ENDODONTIC SYSTEMS AND INSTRUMENTS FOR THE ANATOMICAL, SECTIONAL AND PROGRESSIVE CORONO-APICAL PREPARATION OF ROOT CANALS

Abstract: A root canal is sequentially cleaned in sections from the crown to the apex by dividing it into three sections including an operative coronal portion, an operative middle portion and an apical portion. After an opening is formed into the tooth to provide access into the root canal, the opening is preferably rectified to remove obstructions so that the anatomical root canal can be fully accessed. The pulp material is then sequentially removed from the portion of the root canal above the apical portion of the root canal with a set of instruments (410). The apical portion is then cleaned with another set of instruments (470). An optional set of instruments (440) can also be used to improve the access into the apical portion such that irrigants can be delivered to the apical portion. Cleaning of the pulp material from the root canal also shapes the root canal to ease filling of the root canal with a filling material. The root canal preparation and shaping are completed while maintaining the original anatomy of the root canal. Each file has an abrading portion and terminates at a tip. The files of the set (410) of instruments used to clean the portion of the root canal above the apical portion have properties which enable the abrading portion of the file to conform to the configuration of the root canal while simultaneously moving the file in a cleaning motion.

Description: ENDODONTIC SYSTEMS AND INSTRUMENTS FOR THE ANATOMICAL, SECTIONAL AND PROGRESSIVE CORONO-APICAL PREPARATION OF ROOT CANALS BACKGROUND OF THE INVENTION 1. The Field of the Invention The present invention is related to the field of endodontistry. More particularly, the invention is related to systems and operating methods for the preparation of root canals for obturation. The systems and methods involve the use of at least instruments which are dedicated for specific purposes in the inventive methods and systems and are designed for minimal intrusion into the apical portion. 2. The Relevant Technology To preserve a tooth with a pulp that is diseased or is potentially diseased, it is generally necessary to remove as much of the pulp material as is possible from the pulp canal of the tooth, to shape the root canal(s) without excessively weakening the root canal walls, to prevent or minimize the presence of bacteria through the use of irrigants and dressings, and lastly, to clean the walls of the root canal(s) by removing the smear layer created during instrumentation of the root canal(s). These steps are all done to prepare the root cavity for sealing or obturation which involves filling the root canal with biocompatible materials, such as gutta percha, before the pulp cavity is sealed, thereby promoting the healing and functional recovery of the tooth. This procedure is referred to as root canal therapy. As indicated hereinabove, root canal preparation involves pulp removal, cleaning of the root canal walls and shaping of the canal walls. This is typically achieved through a guided procedure with the use of instruments which are moved either manually, mechanically or by combinations thereof. These instruments are files or bits that are configured to bore and/or cut. Mechanical instrumentation can be achieved through the use of endodontic handpieces coupled to instruments such as files. The endodontic handpieces can impart rotational motion to a file, reciprocal motion by alternately rotating a file clockwise and counterclockwise, sonic movements or ultrasonic movements. Before endodontic therapy is begun, a preoperative x-ray image is obtained to assess the health and the pathological status of the tooth and to determine the approximate initial length of the root canal(s). Once the approximate length of the root canal(s) has been determined, an instrument can be selected for use in the root canal which has an appropriate working length. The schematic representations shown in Figures 1 A and IB are similar to a typical x-ray image. As shown in Figures 1 A and IB, an x-ray image of teeth generally show teeth 10 with sufficient clarity to view some of the properties of roots 12 and the root canals 14 located therein, particularly the location of the radiographic apex 17. The location of the radiographic apex often does not coincide with the true apical terminus of the canal just beyond the apical foramen 16. The distance between radiographic apex 17 and a fixed reference position on the occlusal surface of a tooth is used to determine the working length of the instruments. Figure IB, which is an enlarged view of root 12a shown in Figure 1A, shows the relative position of the radiographic apex designated at line 17 in relation to that of the endodontic apex and the anatomical apex designated respectively by lines 18 and 19. This condition is typical of an apex in living teeth, whereas a pathological apex can appear in a partially autolyzed state, as shown in Figure 34C. Preoperative or intraoperative x-ray images of a tooth requiring endodontic treatment, such as the x-ray image depicted in Figure 1A, are obtained by lingual placement of film packets as shown in Figure 2 at 22 which is supported by an x-ray film packet holder (not shown) and a long cone x-ray head (not shown) located outside of the cheek. Although, x-ray images obtained as shown in Figure 2 from a buccal-lingual x-ray projection are generally useful for determining the overall characteristics of a tooth, the approximate initial length of the root canal(s), and the working length for a file, such images provide only limited information regarding the overall anatomy of the root canal. The information is limited because only one dimension of the overall anatomy of the pulp cavity can be viewed in vivo. In the standard buccal-lingual projection such images show only a linear profile of the root canal and cannot show a tridimensional view of a tooth and its root canal(s). Although, it would be very helpful to view a tooth from a position between the teeth or from the interproximal space such a mesial-distal view cannot be clearly produced when the tooth is still positioned in a patient's mouth. Since information is needed of all three dimensions in order to correctly understand the overall anatomy of the root canal and yet only two-dimensional images of a tooth can be obtained, x-ray images are sometimes relied on to reach incorrect conclusions regarding the anatomy of the root canal. More particularly, if not properly evaluated, x-ray images can be misleading as to the actual length of the root canal and the position of the foramen or foramina. The difficulties encountered by an endodontist in assessing the overall anatomy of teeth from just the x-ray images obtained from buccal-lingual x-ray projections can be clearly identified with reference to Figures 3-6. Figures 3A-6A are longitudinal cross- sectional schematic views of extracted teeth taken from the front or back of the respective tooth which correspond with typical images obtained from buccal-lingual x-ray projections. Figures 3B-6B are longitudinal cross-sectional schematic views of the same extracted teeth shown respectively in Figures 3 A-6A taken from the mesial-distal or side view that cannot be obtained or seen while the teeth are still positioned in a patient's mouth. Note that by varying the angle of incidence of the x-ray beam mesiodistally and distomesially additional x-ray images can be made which provide some additional information about the anatomy of the tooth. However, we can never obtain a three- dimensional image! Figures 3-4 illustrate that in order to properly prepare a root canal it is necessary for practitioners to rely heavily on their experience, knowledge acquired through a study of typical anatomical structures, and on their visually acquired experience with longitudinal and transverse dental cross-sections at various heights. Figure 3A depicts a lower premolar 30 from the buccal-lingual view of the tooth which shows root 32 and a root canal 34 therein that appears to be rather narrow and to have a relatively uniform perimeter along its length. Figure 3B, however, shows that when seen from the mesial- distal view, the root canal is initially fairly wide over more than half its length, and then tapers significantly before reaching the apical foramen 36. Comparing Figure 3A with Figure 3B clearly shows that when limited to knowledge derived from an x-ray corresponding to the image shown in Figure 3A, the practitioner may not be able to accurately assess the anatomical structure of the root anatomy. Additionally, Figure 3C shows that instead of an apical foramen there may be double, triple or quadruple foramina as indicated in research performed by the applicant and by others. The triple foramina 36a, 36b and 36c shown in Figure 3C may not be detectable when viewed only from the buccal-lingual view shown in Figure 3A. Figure 4B depicts an upper premolar 40 with roots 42a and 42b and root canals 44a and 44b located therein. Comparing Figure 4A and Figure 4B reveals a problem which is similar to the problem revealed by comparing Figure 3A with Figure 3B. More particularly, by comparing Figure 3 A with Figure 3B or Figure 4A with Figure 4B, it is easily understood that the practitioner may not be able to accurately assess the anatomical structure of the root anatomy when limited to knowledge derived from an x-ray image. Since the configuration of pulp chamber 48 may be difficult to accurately and fully ascertain from only an x-ray image, a practitioners also relies, as indicated hereinabove, on accumulated experience, knowledge of dental anatomy, and knowledge of typical anatomical structures. The potential inaccuracy of a conclusion derived from information obtained from an x-ray image is further illustrated by comparing Figure 5 A and Figure 5B and also Figure 6 A with Figure 6B. More particularly, as discussed hereinbelow, Figures 5-6 show that practitioners encounter anatomies with widely varying aberrations and intercommunications of root canals which may not be apparent to the practitioner from the limited information derived from x-ray images. Figure 5A depicts a mandibular or lower incisor 50 from the buccal-lingual view of the tooth which shows root 52 and root canal 54. Figure 5B depicts the same lower incisor 50 from the mesial-distal view of the tooth. The mesial-distal view shown in Figure 5B clearly reveals that root canal 54 branches and then rejoins to have a single foramen 56. Root canal morphological variations, such as that shown in Figure 5B, may not be detectable by a practitioner who relies solely on a preoperative or intraoperative x-ray image, such as the image of lower incisor 50 shown in Figure 5 A. Similarly, a root canal may branch without merging so as to yield multiple foramina, such as the root canal of a lower first molar 60 shown in Figures 6A-6B. Again, the buccal-lingual view, as shown in Figure 6A, provides inadequate information when compared with the depiction taken from the mesial-distal view of mesial root 62b in Figure 6B. Figure 6B reveals that branches 64a and 64b do not merge and accordingly have two foramina 66a and 66b. In addition to the morphological variations in anatomy as discussed above, consideration should also be given to the substantially different perimetrical configurations of root canals, as revealed by various dental cross-sections shown in Figure 7 and Figure 8. Additionally, the shape of root canal perimeters varies not only between different types of teeth as shown in Figure 7 and Figure 8 but also along the length of a single root canal of a tooth as is illustrated in Figures 9A-9B. Figure 7 shows a classification system devised by A. Latrou which divides the perimetrical anatomies of root canals into those that have primarily a tubular moφhology and those that have primarily a laminar moφhology. Examples of root canals with tubular perimetrical anatomies are shown at 70, 71, and 72 which are respectively primarily oval, round and triangular. The laminar perimetrical anatomies include root canals with essentially slit-like configurations such as those shown at 73, 74, and 75 which are respectively primarily straight, semi-lunar shaped, and figure eight shaped due to the vestibular and lingual bulges. The laminar shape is more common than the tubular type root canals. Figure 8 shows cross-sectional views of the middle third of different teeth 80a-801 that have been extracted and then cut along a transverse cross-section of the tooth to show root canals 82a-821 as well as corresponding pulp chambers 84 and floors or cervical aspects 86. Conventional file instruments 88 are also shown inserted into root canals 82. From this view, which can only be seen in vitro, it is evident that a certain degree of variation occurs in the perimetrical anatomy of the pulp cavity of teeth. The practitioner may at first be unaware of such variation; however, the practitioner must keep in mind the possibility of such variation while working with instruments in the root canal so that all of the canal walls will be treated and the irregularities caused by greater parietal thicknesses can be removed without unduly weakening the walls. Figures 9A depicts a maxillary right upper first molar 90 with dashed cutting lines included to identify the division of the tooth into transverse cross-sections for segmentation as shown in Figure 9B. Figure 9B displays roots, 92a, 92b and 92c of molar 90 as cut into four respective segments, 100-103, to clearly show the variations of root canals 94a, 94b and 94c. Also displayed in Figure 9B are segments 104 and 105, which respectively contain the pulp chamber 98 and its floor. A comparison of the perimeters of root canals 94a, 94b and 94c starting at segment 104 as each root canal tapers to its respective apices 96a, 96b and 96c, clearly shows that the perimeter anatomy varies and transitions in configuration along the entire length of each root canal. So not only must a practitioner deal with root canals having different shapes as discussed in reference to Figure 7 and Figure 8, but the practitioner must also utilize an instrument in a root canal with a perimetrical or circumferential anatomy that varies depending on the height at which the observation is made. From the discussion above, it is apparent that when a practitioner views a preoperative or interoperative x-ray image of a tooth, the practitioner can only guess about the actual anatomy of the pulp cavity and the root canal(s) of the tooth. While the practitioner may be able to confirm that a root canal has been cleaned along the length of the pulp chamber from the coronal portion to the apex of the root, the length that has been contacted or abraded by the file may only be a portion of the root canal system. Since it is impossible to obtain a mesial-distal view of the root canal or to view the perimetrical anatomy on different points along the length of the root canal, the practitioner is prevented from obtaining a proper preliminary understanding of the overall root canal anatomy in order to assess the necessary relationship between the canal walls and the instrument inserted in the root canal. Accordingly, as shown in Figure 10A and Figure 10B, when a file instrument such as instrument 114 is inserted as far as the apex into a root canal such as canal 112a of tooth 110a or canal 112b of tooth 110b and then rotated, significant portions are not cleaned. The inability to clean all surfaces of a root canal by merely inserting and rotating a file instrument in a root canal is further illustrated by Figure 8. Figure 8 depicts the position of file instrument 88 in transverse cross-sectional views of root canals after file instrument 88 has been inserted to the apex of each respective root canal. Figure 8 clearly shows that simply drilling from one position into the root canal will often miss large sections of the perimeter of the root canal, thereby leaving portions of live, diseased or necrotic pulp material undisturbed. If the operator is unable to apply the instrument to every segment of the perimeter of the canal, the undisturbed pulp material may ultimately cause undue pain, lengthy healing times or even cause the procedure to fail. Solvents or irrigants such as sodium hypochlorite may be used to further clean the root canal. The next step is neutralization or obturation of the root canal which involves coating or filling the root canal with a plastic obturation material such as heated gutta percha. The object of obturation is to prevent the ingress of bacteria or tissue fluids which might act as a culture medium for any bacteria remaining within the root canal system by sealing the system. In order to reach the recesses with the filling material that cannot be treated with the instruments, vertical pressure must be applied with a plugger; however, there is never any assurance that all of the necrotic residue has been coated. There is also a risk that such techniques will cause infected material to be pressed beyond the apex. Such an extrusion of infected material beyond the apex is very undesirable as it may contain polymicrobial loads or charges that may produce damaging bacteremia or cause chronic inflammations of the apical and periapical tissues. Based on all of the foregoing observations, it can be concluded that inadequate attention is given to understanding the dental chambers on a three-dimensional basis, the varying configurations of the perimeter of the root canal(s), the diameter of the canals, and the thickness of the walls. Note that research is still needed to investigate and catalog the thickness of dental walls in order to increase understanding amongst practitioners. The inability to fully identify the anatomy of the pulp cavity restricts the ability of the practitioner to confidently conclude that the procedure has been successful. Although problems may result from having incomplete information regarding the anatomy of a particular root canal, many practitioners using conventional methods and instruments are not overly concerned with completely cleaning the entire root canal since their failure rate is not at an unsatisfactory level. While these conventional methods and instruments may result in satisfactory failure rates, it would be very beneficial to still lower the failure rate and to better preserve the integrity of teeth. As discussed hereinbelow, most of the methods and instruments that have been and continue to be employed and produced are relatively arbitrary with regard to root canal anatomy. To compensate for the limited understanding of the inability to contact all root surfaces and the lack of knowledge of the actual anatomy of the root canal, many working methods have been devised, which in turn have prompted the creation of a multitude of instruments of varying diameters and sizes. With regard to operating procedures, there are two basic methods from which all of the canal-preparation techniques can be derived. These methods have been inteφreted by various authors in an operational context and also in terms of the instrumentation. The primary conventional systems and methods for removing pulp material from the root canal of a tooth are the apico-coronal (step-back) technique and the corono-apical (crown- down) technique. Although these conventional cleaning techniques both rely generally on sequential increases in the diameter of instruments inserted into the root canal, the step-back technique involves cleaning the root canal from the apex toward the crown while the crown-down technique involves cleaning the root canal from the crown down to the apex. Each has its own unique benefits and disadvantages which are discussed hereinbelow. The step-back technique involves the use of various sets of file instruments which are sequentially inserted into a root canal after the root canal has been exposed by removing the roof of the pulp chamber as depicted in Figure 11 A and Figure 1 IB. More particularly, before pulp material 160 can be removed in accordance with the step-back technique, an instrument, such as instrument 120 shown with bur 122 in Figure 11 A and Figure 1 IB, is utilized to remove the overhanging portions of enamel 152 and dentin 154 in order to provide access into the pulp chamber 156. Figure 12 depicts a set of step-back file instruments with each file instrument 130 comprising a handle 132 connected to a file 134 or a shaft with tines or an abrading portion. Each file has a tip 136 opposite a top end 138 where file 134 joins handle 132. As viewed in Figure 12 from left to right, the diameter at top end 138 of each file increases progressively from the smallest to the largest such that the diameter of 138a is less than the diameter of 138b. The diameter of each successive file at tip end 136 is also successively larger. Accordingly, the taper of each file remains essentially the same even though each file is progressively larger that the preceding file. In the step-back technique, the apical portion of the tooth is prepared first and then the remainder of the canal is flared from apex to crown. This process essentially involves inserting a series of progressively larger files into the apex of the root canal and rotating each file and/or moving the file up and down in a longitudinal motion until a file can be inserted that is considered to be a suitable standard size for completing the process or that meets some resistance to rotation. The rest of the canal is then flared by sequentially using each file in the set, as shown in Figure 12, with each file being larger than the preceding file and by alternately advancing and then withdrawing each instrument. Figure 13A depicts a molar 150 being prepared by the step-back technique after the removal of enamel 152 and dentin 154 that extend into pulp chamber 156, and after the first stage of the step-back technique has been completed. The first stage of the step- back technique involves the insertion of a file into pulp chamber 156 and into root canal 158a in order to remove material 160 in the lower portion of the canal above the apex or apical end 162a. After the portion above apex 162a is cleaned, each file shown in Figure 12 is sequentially inserted downward toward apical end 162a of root canal 158a, starting with file instrument 130a as shown in Figure 13 A. As a result of this technique, the diameter of the area being contacted at the apical portion is increasingly larger. Figure 13B is a cross-sectional view taken along cutting line 13B--13B in Figure 13A of tooth 150 during cleaning of root canal 158a with file instrument 130a in the step-back technique. Insertion of the files of the other file instruments 130b and 130c may further clean out material 160 because each file has an increasingly larger diameter. With each increase in diameter, the rigidity increases and the flexibility of the files decreases. As a result, it becomes increasingly difficult for the files to adjust to or to follow the contours of the perimeter surfaces of the root canal. This reduced flexibility also increases the likelihood that the files will fail to contact some portions while removing too much of the surrounding dentin 154 in some areas through excessive abrasion and resulting in overthinning of the walls. Note that the views depicted in Figures 13A and 13B depict the problem previously discussed with regard to the difficulty in assessing the actual root canal anatomy in vivo. When viewed in Figure 13 A, it appears that the root canal has been cleaned; however, Figure 13B shows that a significant portion of material 160 remains. Accordingly, when the root canal is viewed in an x-ray photograph which is the same view shown in Figure 13 A, a practitioner may mistakenly believe that the tooth has been adequately cleaned. This mistaken belief may be further incorrectly relied on as the root canal is widened by the insertion of the larger files which gives an impression of complete cleaning. There is resultingly some possibility for failure of the root canal therapy due to incompleteness. Not only is the completeness effected by the use of a set of files wherein each file is more rigid than the preceding file but the ability to safely move the file within the canal is also limited. More particularly, the increasing rigidity results in decreased ability to negotiate the curves in the canal. Significant problems that can result from inserting increasingly rigid files and also from initially inserting a file all the way down to the apex includes laceration and transportation of the apical foramen, as well as misdirection and perforation of the wall. As shown in Figure 14 A, after tooth 170 was prepared by removal of portions of the enamel 172 and dentin 174, file 132 was inserted into root canal 176 and perforated apex 178. Perforating the apex can also result from an error in estimating the length of a root canal, by failure of a stop such as stop 140 to remain at a predetermined position or by failure to observe the calibration or graduation hatch markings on the file, which can be used instead of a stop to designate the length. The apex can be perforated by extrusion of the infected material 180 through the apex due to the force exerted by the file on the material as the file is pushed downward to reach the apex. As a result, the periapical region can be invaded and contaminated. The potential for extruding infected material through the apical foramen of a necrotic tooth during the initial insertion of a file instrument all the way down to the apex is a particular disadvantage of the step-back technique. Another disadvantage is that the procedure has identical steps for working in either necrotic or vital root canals. In addition to exposing the tissue surrounding the tooth to the infected material, apical perforations may allow irrigants, amalgam filling or obturating material to flow out of the apex. Such apical perforations, as well as wall perforations, may delay tooth healing and may compromise the outcome of the therapy. Perforations can also occur due to a failure to maintain a proper working length of the instrument during the procedure. As the canal is widened, curvatures are straightened thereby decreasing the required working length needed for the instrument to work. Accordingly, the rubber stop 140 must be adjusted, thereby continually providing an opportunity for the instruments to become contaminated by bacteria. To properly determine the appropriate working length, many radiographs must be taken throughout the operation as the canal is continuously being modified, which alters the length. The time required to obtain the x-ray photographs or images and to adjust the working length of the instruments by repositioning the stops can result in a lengthy process. The step- back technique is also time intensive because a large number of instruments are required to complete the root canal therapy. As shown in Figure 14B, another problem is the formation of ledges such as ledge 182. Ledges can occur when a practitioner attempts to insert a file such as file 134 as far as the apex and the file is too inflexible to properly curve with the root canal or move around a protrusion. When a file is too inflexible to curve or flex as needed and is halted prematurely, the downward pressure exerted on the file, in conjunction with the tendency of the file to straighten itself, causes the tip of the file to dig into the side of the root canal and form a ledge. Such ledges are difficult to bypass; and if the ledge occurs very close to the apex, the ledge may give the practitioner the mistaken impression that the apex has been reached. The crown-down technique was developed for several reasons. It was desired to shape the canal "conically" so as to keep the diameter of the foramen as straight as possible. The crown-down technique was also developed to prevent the discharge of septic material or obturation material from the apex after the initial canal-preparation step and to prevent subsequent vertical condensation due to the vertical pressure used to obturate the canals with heated gutta-percha. Additionally, the crown-down technique was intended to reduce the number of instruments utilized compared with the step-back technique. However, as discussed hereinbelow, significant potential problems may inherently result from use of the crown-down technique. The crown-down technique generally involves the use of a set of file instruments wherein each file in the set of file instruments has a progressively different diameter at the top of the cutting portion of the file, i.e., the point where the file becomes smooth and no longer has cutting capabilities. The smooth portion may have a constant diameter. The diameter at the top of the cutting portion of each file may be either constant or graduated for the entire set of instruments such that the top of the cutting portion of each file is progressively larger than that of the preceding file. As a result of this configuration, the taper of each file is larger than the preceding file in the set. By using such files of increasingly larger diameters, the area that is initially and subsequently abraded, as work proceeds toward the apex, will always be primarily at the top portion of the root canal. Gradual progressive conicity or taper, and the constant diameter of the tip (characteristics which, paradoxically, have been inflated, despite the prior teachings of the present applicant in earlier patents, such as Italian patents No. 1,199,941 and No. 1,169,326, and U.S. Patent No. 4,971,556) are characteristics which are now so standard among the multitude of crown-down instruments made of nickel/titanium that have been introduced onto the market, that competitors have shifted toward other features of the instruments. For example, increasing value is being attached to the so-called "overall" originality of an operating procedure that uses so-called "dedicated" instrumentation to solve the multiple problems associated with root canal preparation in terms of ergonomics, operational safety, the time and cost of the procedure, and the likelihood of success. One example of the operational deficiency of the crown-down method lies in its association with instruments made of nickel/titanium. Based on the greater flexibility of files formed from nickel/titanium compared with files formed from steel, proponents of the crown-down method in conjunction with nickel/titanium files assert that such files can better follow the curvatures of a root canal. Additionally, it has been asserted that such files are more likely to stay in the center of the root canal, thereby decreasing the likelihood of ledging or perforating the root canal walls. As set forth hereinbelow in greater detail, each material has its own unique advantages and disadvantages. The ability of a nickel/titanium file to stay in the center is not necessarily desirable, in view of the moφhology and perimetrical variety of root canals, and particularly the variety in the upper two-thirds of laminar root canals. In fact when rotation is imparted to an instrument that stays in the center of the canal, the file instrument works simultaneously and indiscriminately on all of the walls within reach of the file. Since root canal walls do not have equal thicknesses in all directions and at all different points along a root canal, some walls can be overthinned or perforated, while other walls remain untouched. Moreover, because nickel/titanium files are more flexible than steel files, they tend to follow the path of least resistance and therefore cannot be used, in the same way as steel files, to be applied actively and intentionally by the operator. As a result, even when the operator knows the thickness of a particular portion, such as an interference or obstruction which the operator desires to rectify or straighten, the operator lacks the freedom to aggressively drive the file as needed and clean the portions that are difficult to reach. Accordingly, when a nickel/titanium file is used to clean a non-cylindrically shaped root canal, the file moves only at the center of the canal and/or the area of least resistance and fails to remove all of the necrotic tissue. Figures 15 A, 15B, 15C , 15D and 15E depict transverse cross-sections of tooth 190 that has been cleaned in a manner that has resulted in either overthinning of root canal walls, perforation of a root canal wall, excessively weakening of the walls of the tooth or a failure to fully contact all of the canal walls. These problems can be easily caused by the passive, self-guiding use of nickel/titanium files with progressively larger tapers in the transition from the first instrument to the next one in the set. These problems can also be caused by the increasing rigidity, in accordance with the crown-down technique, which prevents the files from being laterally moved to enable the files to clean the entire perimeter of the root canal. The cross-sections shown in Figures 15A-E may be considered independently from each other as being cross-sections from different teeth or from a single tooth such that Figure 15 A shows two roots 192a and 192b of a tooth 190 while Figures 15B-15E show root canal 194a as the root canal tapers to the apex. Figure 15A depicts the overthinning that can occur to the furcation walls of root canals 194a and 194b near the bifurcation as a result from the indiscriminate thinning of the distal walls of the root canals by maintaining a file instrument in a central location during working rotation. The resulting boreholes are shown at 196a and 196b while the outlines of root canals 194a and 194b before cleaning are shown in phantom lines. Such overthinning and potential furcal perforation can have devastating results. The inability to adequately direct a file used in accordance with the crown-down technique based on the practitioner's knowledge of the relative thicknesses of the portions of canal walls is a significant disadvantage of the technique. Figure 15B shows a lateral perforation that has occurred when a hole was made through dentin 198 and cementum 197 during the cleaning of root canal 194a. The lateral perforation resulting from the formation of borehole 196a may be obscured from the x-ray due to concavities or curvatures in the root canal. The practitioner may then mistakenly conclude that the root canal has been successfully cleaned without realizing that there is a perforation. In Figure 15C, the segment shown of root canal 194a was overly thinned during the cleaning of root canal 194a as borehole 196a is shown extending through dentin 198 and into the cementum 197. As mentioned in reference to Figure 15B, the formation of borehole 196a may be obscured from the x-ray view. As a result, the practitioner may not realize that the borehole extends into the cementum and may therefore mistakenly conclude that the root canal treatment has been successful. Infective bacteria that remained in the root canal, perhaps in the portions that were not contacted with the files, as well as toxins produced by the bacteria may then permeate through the cementum and cause infection or other complications. Figure 15D provides an example of a cross-section of a laminar-type root canal cleaned by the crown-down technique which may result in successful root canal therapy since the instrumentation has not resulted in a perforation and the cementum 197 has not been exposed. Although, problems such as perforations or overthinning have been avoided, Figure 15D shows that large portions of root canal 194a remain untouched despite the change in moφhology through the formation of large borehole 196a. Note that the change in the moφhology of the canal shown in Figure 15D resulting from crown-down technique instrumentation occurs due to drilling in a passive, circular manner with instruments having gradual and progressive tapers. The failure to contact significant portions of a root canal while forming a large borehole in a root canal as shown in Figure 15B-D is a very typical result of the crown-down technique since most root canals can be characterized as a laminar-type root canal. It would be preferable to avoid the risk posed by failing to contact significant portions of the root canal as shown in Figure 15D. Since the practitioner is prevented from removing and cleaning essentially all pulp material, the practitioner cannot be assured of the reliability of the treatment. Additionally, the practitioner may not suspect that the working instruments have failed to contact every segment of the root canal as use of a set of files with increasingly greater tapers can contribute to a potentially incorrect conclusion that cleaning by such a conventional process has resulted in removing all material from root canal 194a. Further, the x-ray view of tooth 190, as with the step-back technique shown in progress in Figures 13 A and 13B, would give the impression that the root canal had been cleaned. It should also be remembered that while rotation of a set of passively actuated files, with increasingly greater tapers, in the center of the canal, in accordance with the crown-down technique, may yield a configuration as shown in Figure 15D and result in successful root canal therapy, there is a significant hazard, as shown in relation to the Figures 15 A-C, due to the passivity of the instruments when linked to canal diameters and wall thicknesses that are still statistically unknown. As in the configuration shown in Figure 15D, the configuration shown in Figure 15E may also result in successful root canal therapy ~ but only for canals of the wholly tubular type. Although, borehole 196a does not extend through dentin 198 and into the cementum 197, the diameter of the preparation or borehole 196a is nevertheless significantly larger than that of the original root canal was as shown by the phantom lines at 194a. The excessive thinning of the dental wall may resultingly significantly weaken the resistance of the walls to the stress of chewing, and may also cause a fracture of the root. From the above discussion in relation to Figures 15A-E, it is clear that the actual moφhology of the canals is not sufficiently considered when using this method and that the use of files with increasingly larger tapers limits the range of motion of the files. More specifically, due to the use of files with successively larger tapers which therefore are increasingly rigid, each file, if actuated passively, is primarily limited to being rotated without substantial lateral movements guided by the operator. Since the majority of files are of the laminar type, this limitation poses a significant problem. Without the ability to laterally move the files, it is not possible to make contact with every segment of the perimeter of the canal and some portions may receive too much contact. In any event, if the files are rotated passively in a laminar canal or a canal which has a laminar-type anatomy for the first two-thirds of the canal, the result is a circular opening whose diameter corresponds to that of the file that was used. The file typically stays in the center of the canal during rotation, such that the tip of each file acts like a fulcrum and "ideally" stays in the same position as a rotation point. Since each successive file can move less laterally, each file simply makes a bigger borehole than the preceding file. Accordingly, the files cannot clean a root canal without significantly altering the original anatomy by leaving a footprint or borehole corresponding to the configuration of the instruments used. More specifically, the result is a footprint or borehole with a perimeter that corresponds to the perimeter of the biggest file that extends well beyond the original anatomy of the root canal and yet in most instances does not adequately clean significant portions of the root canal. As discussed above, the flexibility of the files used in the crown-down technique, which are typically formed from nickel/titanium, prevents the files from being successfully urged against the perimeter or against the various surface features of the root canal. As also discussed above, the flexibility of the files also increases the tendency of the files to remain in the center or at the location where less resistance to movement is encountered. Accordingly, the flexibility of the files also contributes to the configuration of borehole 196a, which substantially deviates from the original anatomy of the root canal 194a. There are also other disadvantages to the use of nickel/titanium files. The flexibility of nickel/titanium files increases the likelihood that the file may bend and be deformed upon encountering a hard substance. Since nickel/titanium files are more fragile and more flexible than stainless steel files, the nickel/titanium files can break more easily and unexpectedly than steel files. When a nickel/titanium file instrument is used with a large file diameter the flexibility decreases to the point of being as rigid as stainless steel and yet breaks more easily. More particularly, beyond a certain diameter, the upper halves of larger diameter files are still as rigid as that of steel files while the flexible lower halves of nickel/titanium file instruments are more prone to break. Additionally, rotation of a file in a canal that has a laminar upper two-thirds exposes the tip of the file to the risk of breaking when the tip of the file is embedded or stuck in a canal whose diameter is smaller than its own diameter! To avoid breaking the tip when it is embedded or stuck in a canal whose diameter is smaller than the diameter of the tip, operators who use nickel/titanium files are advised to employ catheterization in order to obtain a prophylactic widening of the canal, using a series of instruments with increasingly larger tip diameters. Another disadvantage of nickel/titanium files is that nickel embodied in the alloy may potentially result in an allergic reaction. Further, nickel/titanium files costs about four times as much as steel files and yet nickel/titanium files generally wear out faster than steel files. Nickel/titanium files wear out so quickly that some manufacturers mark their products as being intended for single use only. Moreover, the crown-down instruments currently available on the market, almost all of which are made of nickel/titanium, in some respects violently conflict with the use of the crown-down method, because, paradoxically, these instruments are smooth in areas where the method requires that they first perform a cutting action. The reason for this deficiency lies in the length of the abrading portion of the instruments, which portion is only 16 mm long and which extends into a smooth portion leading to the handle, onto which rubber stops are affixed, or into which millimeter-based calibration marks are engraved in order to allow visual control of the working depth of the instrument in the canal. For example, note in Figures 13 A and 13B that when file 134a is inserted into root canal 162a that the abrading portion 138a is not long enough to contact the dentinal shelves 166, instead the upper portion of the file is smooth shank portion 136a. Since the length of the root canal often exceeds the standard 16 mm length abrading portion of conventional instruments, see Table 1 hereinbelow, we may reasonably ask how an instrument which, according to the crown-down method, is supposed to prepare a canal starting at its coronal third, can perform this task if its coronal segment is smooth! Table 1/Average Root Canal Lengths Obviously, from a review of the average root canal lengths in Table 1 , significant segments of a root canal cannot be abraded by standard 16 mm long abrading portions of conventional files and are contacted only by the smooth portion of the files. Although, the crown-down technique typically enables a practitioner to more efficiently clean a root canal than the step-back technique, they both require the practitioner to utilize many different instruments. The need to frequently change the cleaning instrument results in significant time requirements for cleaning a root canal. However, careful instrumentation in accordance with either tedious time consuming method does not avoid the problems set forth above in relation to apical perforation, wall perforation, overthinning or failure to clean all of the wall surfaces. Based on the foregoing observations, methods and systems are needed in the endodontic arts which enable a dental practitioner to remove and clean essentially all pulp material in a root canal requiring root canal therapy. It would also be an advancement in the endodontic arts to provide methods and systems that are based on the three-dimensional reality of teeth and do not relate solely to buccolingual x-ray views, thereby enabling a practitioner to remove and clean pulp material in a root canal without compromising the strength of the walls and the apical anatomy. It would also be a beneficial development in the endodontic arts to provide methods and systems which encourage perimetrical contact of the instruments with the canal walls. Additionally, it would be an advancement in the endodontic arts to provide methods and systems that enable a practitioner to remove and clean pulp material in a root canal in a manner that is less likely to result in failure due to bacterial contamination, overly thinning the root canal, perforations or due to infected material being pushed beyond the root from the coronal aspects of canals. Finally, it would also constitute progress in the endodontic arts to provide methods and systems which yield a predictable success rate, minimal risk of breaking an instrument, lower costs, and an abbreviated operating time or an operating time that is at least as efficient as conventional techniques. SUMMARY OF THE INVENTION Some of the features of the invention are summarized hereinbelow. Root Canal Terminology Rather than speaking generally of "canals" in connection with operative practice, the present applicant prefers the term "canal element", in order to emphasize that each canal has its own "anatomical personality" with which the operator should be familiar. For example, one canal element may have a perimeter shape which is primarily laminar according to the Latrou classification system discussed in the above section entitled the "Background of the Invention" while another canal element may be tubular. Even in a single tooth which has multiple canal elements, it is important to bear in mind that each canal element has a unique moφhology. When referring to a polyradiculated tooth, which has more than one canal element, such as an upper first premolar, applicant prefers the term "canal apparatus" when referring to a set of canal elements. Applicant utilizes a terminology based on the methodology disclosed herein. The term "operative canal" refers to the pathway which starts at the occlusal surface of the tooth, continues with the cameral wall segment and the anatomical canal perse, and finally reaches the foramen. Of course, the anatomical root canal extends from the pulp chamber or the floor of the pulp chamber to the apex. The operative root canal is divided into three sections or portions which are referred to herein as "the operative coronal portion", "the operative middle portion" and "the apical portion". The operative coronal portion essentially includes the access cavity walls. The operative middle portion is the upper portion of the anatomical root canal while the apical portion is the lower portion of the anatomical root canal. A typical apical portion is the last or bottom 3 mm of the anatomical root canal. The terms "operative coronal portion", "operative middle portion" and "apical portion" are unique terms that are distinct from the terminology conventionally utilized to refer to segments of a root canal. In the conventional crown-down method, the canal is customarily divided into the so-called "three thirds", including: the crown, the middle third, and the apical third. In reference to the conventional crown-down method, it is common to use the term "coronal third" to refer to the first part of the "anatomical" canal, originating at the floor of the pulp chamber or the upper limit of the middle third into which a tooth is customarily divided, with a theoretical line at the height of the neck. Methodology Overview During the root canal therapy, the pulp chamber can be opened to expose the anatomical root canal by any conventional method or instrument. Additionally, conventional methods and instruments can be used to prepare the operative coronal portion. However, unique methods and instruments are used in the operative middle portion while preferably simultaneously abrading the operative coronal portion. Additionally, after the operative middle portion has been cleaned, unique methods and instruments are used to improve access into the apical portion and to then clean the apical portion. The present applicant developed the methodology disclosed herein based on the anatomical reality discussed above in the section entitled "Background of the Invention". By envisioning the canal in which they are operating as starting at the occlusal surface, practitioners can immediately identify any "interferences" or obstructions, as well as any protrusions of enamel, which may be disregarded. As a result, the instruments disclosed herein come into contact with every segment of the canal walls, including the obstructions, in order to achieve anatomical widening and also the rectification or straightening of the first two portions of the canal which include the operative coronal portion and the operative middle portion. This procedure opens the pathway for the preparation of the apical portion of the canal. The methodology disclosed herein involves the use of distinct instruments in the three portions of the anatomical root canal in different phases such that the root canal is cleaned progressively and sectionally. The instrument(s) associated with each phase have been designed specifically for that particular phase and accordingly have unique customized characteristics and features. The instruments are described hereinbelow after explaining the procedures for completing each phase. By cleaning the root canal in sections, the instruments can be adapted to the perimetrical or perimetral anatomy of the root canal. As a result, the entire perimeter or substantially all of the perimeter is contacted and cleaned along the length of the perimeter without substantially altering the configuration of the perimetrical anatomy. For example, a perimetrical anatomy that was primarily tubular or laminar perimetrical anatomy will be enlarged but will still be primarily tubular or laminar. There will not be a large round borehole in the canal superimposed on the original perimetrical anatomy which corresponds to the diameter of the file that is used; as is the case with the nickel/titanium files that stay in the center of the canal even when the canal is laminar. Additionally, the invention also enables the practitioner to prepare root canals in accordance with the anatomy of the root canal, even though the practitioner may not have been able to adequately identify the overall anatomy due to the inability to see the root canal as is the case from the mesial-distal view using standard radiography. Further, the invention also enables the practitioner to adapt to the contours of the root canal of all different types of teeth, by guiding instruments that have been designed to come into contact with every perimetrical segment of the walls. Interferences and Rectification The term "interference" refers to everything in the operative canal that hinders the rectilinear insertion of the instruments used, during the final cleaning phase of the procedure, preparation of the apical portion. The term "rectification" refers to the placement of the operative coronal portion or access cavity on the same axis as the operative middle portion. Rectification is achieved through the removal of interferences from the operative coronal portion and preferably from the operative middle portion of the operative canal as well. Instrumentation of the Operative Coronal Portion In this phase, the access cavity is created, after elimination of all of the coronal tissue from a carious and weak tooth, and after removal of any infiltrated restoration(s). The access cavity is also created prior to coronal reconstruction, if considered necessary in order to facilitate the installation of the dam. It is not necessary to perform a prophylactic cuspidal flattening or cuspidectomy in accordance with the methodology as disclosed herein. However, it may desirable to perform a cuspidectomy with some teeth, particularly lateral postcanine quadrants, in order to create a flat reference plane for the stop, to create an approach nearer to the pulpar horns, to eliminate occlusal contact, and to reduce the masticatory stress on a weakened coronal structure. Weakening of the coronal structure is typically caused by the primary carious process and by the subsequent removal of the roof or top of the chamber due to the need to create the cavity that allows access to the pulp chamber and to the root canal. However, in view of the fact that the top of the chamber is the natural connection between the cuspids, and that after destruction of the top of the chamber, which connects the cuspids, the diameter of the base of the cuspidal columns remains weak in terms of resisting lateral masticatory stress; the operator needs to be assured of the usefulness of performing the prophylactic cuspidectomy on the postcanine teeth. Apart from avoiding the risk of fractures, the rehabilitative reconstruction of the root canal element may subsequently be facilitated. Instrumentation of the Operative Middle Portion The most important part of this phase is the determination of the so-called "working length" of the first two portions of the operative root canal including the operative middle portion and the operative coronal portion. The methods for identifying the working length involve the use of x-rays or videography, performed with the aid of a centering device and through use of the long-cone method. After the working length has been determined, then the proper instruments can be selected for use in the preparation of the operative middle portion. The working length is determined by measuring the canal axis from the occlusal plane, in order to arrive at the apical limit of the root as indicated on the x-ray. A distance of 3 mm is deducted from the measured length. The result is the maximum working depth that the operative middle portion instrument(s) should reach. The foregoing calculations also figure in the predetermination of the working lengths for all other instruments utilized in the procedure. The instruments preferably are selected to have files with lengths that are equal to the working length; however, stops may also be used to ensure that the files have the desired working length. The preparation of the first two portions also involves catheterization. Additionally, this phase involves the anatomical widening of the perimeter of the operative middle portion as well as the removal of the interferences from the operative coronal portion and the operative middle portions, thereby allowing the rectification of the first two portions of the operative root canal. One of the instrument used during this phase may have a file with an upper portion that is covered with abrasive material or grit such as diamond particles in order to aggresively abrade the upper region of the operative middle portion and the operative coronal portion. Please note that during preparation of the operative middle portion and rectification of the first two portions, any and all intrusion of the instrument(s) into the apical portion is avoided. The boundary between the operative middle portion and the apical portion has been estimated to be located between 3 mm and 5 mm from the end of the root canal, as shown on the x-ray. After preparation of the operative middle portion and rectification of the first two portions have been completed, the procedure moves to the third stage, in which the apical portion is prepared. After the working length has been determined for the first two portion including the operative coronal portion and the operative middle portion, the operator selects an instrument from a set of instruments designed for use in the operative middle portion. The instruments are preferably held in a mini-container whose length is about the same as the identified working length of the instruments. The contours of the perimeter of the root canal in the operative middle portion are followed as the file of the instrument(s) is flexed or curved against the surfaces of the root canal and simultaneously moved in a cleaning motion. Since the contours are followed, the perimeter is widened and smoothed but the original shape is not substantially altered. Preparation of the Apical Portion After the operative middle portion has been cleaned, the apical portion may be cleaned by several different techniques or combinations thereof. One method involves no abrasive instrumentation within the apical portion just appropriate just insertion of appropriate irrigation instruments. Since removal of the pulp material from the operative middle portion removes the majority of bacteria in the pulp canal, it has been found that it is not necessary to abrade the apical portion. Irrigants are delivered into the apical portion to maintain the debris derived from cleaning the root canal in suspension. The debris is then removed as the particles of the smear layer yielded from the action of the files used to prepare the canal may result in clogging the apical portion of the root canal with a plug. After the debris has been removed, the proper preparation and filling of the apical portion of the root canal can be achieved. By eliminating or minimizing abrasive instrumentation within the apical portion, the potential for complications is diminished. As discussed above in the Background, most errors in performing root canals occur during instrumentation of the root canal. The apical portion is the most delicate part of the root canal and it is the most distally located. Accordingly, it is highly advantageous to just irrigate and then remove the irrigant and debris, since many complications occur during abrasive instrumentation. However, in some instances, it may be necessary to improve access into the apical portion such that an irrigation needle can be deployed to deliver irrigants to the apical portion. Access into the apical portion is improved by widening, for example, at least the entrance of the apical portion or the entire apical portion. Alternatively, another method involves the use of a set of instruments designed for cleaning the apical portion in an abrasive manner. Such a method may be initiated directly after the operative middle portion of the operative root canal has been cleaned. However, it may be necessary to have two phases of instrumentation within the apical portion of the operative root canal including widening and abrasive cleaning of the apical portion. More particularly, it may be necessary to improve the access into the apical portion before performing the abrasive instrumentation by widening the transition between the operative middle portion and the apical portion to enable irrigants to be delivered into the apical portion. Before preparation of the apical third is begun by one of the above described methods, the apical and periapical condition of the element is evaluated, in accordance with the following guidelines. For living or necrotic teeth "without rearrangement of the apex" or apical rarefaction, the instrument(s) should be kept no closer than 2 mm from the apex as shown on the x-ray image. Conversely, for necrotic teeth with apical autolysis, the preparation work may be performed up to a distance of 1 mm from the apex as shown on the x-ray image. The predetermination of the widening of the canal leading to the apex, and the widening of each root canal for polyradiculated teeth, should be made bearing in mind the guidelines for the widening limits set forth in the moφhometric data provided in Tables 2 and 3. In most cases, the radicular apex contains the final segment of the main canal, which divides into a delta configuration as discussed above in reference to Figure 3C. This structure is hard to detect with x-rays. Therefore, the moφhology of the dental apex is unpredictable, and the location of the junction between the cementum and dentin in any endodontic apex is random. Likewise random is the hypothetical apical constriction that can be detected by the most expert professionals. A degree of confidence can be obtained through the use of electronic measurement devices in living canals that have not been treated with liquid medications, but only when the foramen has been passed, in order to be subsequently withdrawn into the canal with a probe instrument. This maneuver should be avoided in necrotic canals, because of the risk of carrying germs beyond the apex. The guidelines discussed above should be kept in mind when redetermining the approximately working length to the apex after the operative middle portion has been prepared. It is necessary to redetermine the working length as the working length has likely changed due to the instrumentation of the operative middle portion. Instruments The operative middle portion of the operative root canal is cleaned with a first instrument or set of instruments. The root canal, inclduing the apical portion, is then cleaned with an irrigation instrument. An optional second instrument or set of instruments can then be used to improve the access into the apical portion to enable irrigants to be delivered into the apical portion from an irrigation needle. An optional third instrument or set of instruments is provided to abrasively clean the apical portion of the operative root canal after the operative middle portion of the root canal has been cleaned and after the access into the apical portion has been widened. Each instrument in the first set of instruments comprises a handle connected to a file with an abrasive surface or in other words a shaft with tines or an abrading portion. Each file has a length such that the operative middle portion of the operative root canal is cleaned without significantly removing pulp material from the apical root portion. Additionally, each file is designed to have a taper that is larger than the taper of each preceding file. Each file or shaft has an abrading portion for abrading the surfaces or walls of the root canal. In contrast to conventional files, as set forth in greater detail hereinbelow, the abrading portion may extend along the entire length of the file to enable the instrument to be used to clean the operative middle portion while also abrading the operative coronal portion. The files of the instruments in the first set are designed such that each file has sufficient flexibility to be flexed or curved to urge the abrading portion against the surfaces of the root canal and sufficient rigidity to apply pressure against the surfaces of the root canal as the abrading portion of the file is urged against the surfaces of the root canal and simultaneously moved in a cleaning motion. Additionally, the files have adequate resilience to avoid being substantially deformed as the file is flexed or curved to urge the file, particularly the abrading portion, against the surfaces of the root canal. Each instrument in the optional second set of instruments used to improve or widen the access for the introduction of an irrigation needle to the apical portion comprises a handle connected to a file. Each file terminates at a tip and each file is configured with an abrading portion. Each file has a length sufficient to at least approximately reach the apex and to enable the abrading portion of the files to improve the access into the apical portion of the root canal. Each instrument in the optional third set of instruments used to clean the apical portion comprise a handle connected to a file. Each file terminates at a tip and each file is configured with an abrading portion. Each file has a length sufficient to at least approximately reach the established apical working limit and to enable the abrading portion of the files to substantially contact and clean the pulp material in the apical portion of the root canal. The tip of the file is preferably rounded to prevent ledging. These and other features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS In order that the manner in which the above-recited and other advantages of the invention are obtained, a more particular description of the invention briefly described above will be rendered by reference to a specific embodiment thereof which is illustrated in the appended drawings. Understanding that these drawings depict only a typical embodiment of the invention and are not therefore to be considered to be limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings listed hereinbelow. Figure 1A is a perspective view of an x-ray image of several adjacent teeth taken in vivo. Figure IB is an enlarged perspective view of a root of a tooth shown in Figure 1 A. Figure 2 is a perspective view of an x-ray film positioned adjacent to teeth to produce an image as shown in Figure 1 A. Figure 3 A is a longitudinal cross-sectional view of an extracted lower premolar to show the anatomy of the tooth from the buccal-lingual view. Figure 3B is a longitudinal cross-sectional view of the extracted lower premolar shown in Figure 3A from the mesial-distal view. Figure 3 C is an enlarged longitudinal cross-sectional view of an apex which divides into a delta configuration having three apical foramina. This configuration is presented as a possible alternative to the configuration of the tooth shown in Figure 3B. Figure 4 A is a longitudinal cross-sectional view of an extracted upper premolar to show the anatomy of the tooth from the buccal-lingual view. Figure 4B is a longitudinal cross-sectional view of the extracted upper premolar shown in Figure 4A from the mesial-distal view. Figure 5 A is a longitudinal cross-sectional view of an extracted lower incisor to show the anatomy of the tooth from the buccal-lingual view. Figure 5B is a longitudinal cross-sectional view of the extracted lower incisor shown in Figure 5A from the mesial-distal view. Figure 6A is a longitudinal cross-sectional view of an extracted lower first molar to show the anatomy of the tooth from the buccal-lingual view. Figure 6B is a longitudinal cross-sectional view of the extracted lower first molar shown in Figure 6A from the mesial-distal view. Figure 7 is a cross-sectional view of extracted teeth which have been cut along into transverse cross-sectional segments to show the general categorization of root canal perimetrical anatomies. Figure 8 is a cross-sectional view of extracted teeth which have been cut along into transverse cross-sectional segments to show the anatomy of various root canals. Figure 9A is a schematic perspective view of an extracted maxillary right first molar with cutting lines which show the division of the tooth into transverse cross- sectional segments. Figure 9B depicts the cross-sectional segments of the molar shown in Figure 9 A to clearly show the variations of the root canals. Figure 10A is a perspective view of a prior art instrument cleaning a tooth that has been partially cut-away to reveal the inability of the instrument to clean the root canal. Figure 1 OB is a perspective view of a prior art instrument cleaning another tooth that has been partially cut-away to reveal the inability of the instrument to clean the root canal. Figure 11 A is a longitudinal cross-sectional view of a burr being utilized to remove the overhanging enamel and dentin above the pulp chamber. Figure 1 IB is a longitudinal view of a burr extending through the enamel and the dentin into the pulp chamber. Figure 12 is a perspective view of a prior art set of endodontic instruments utilized in the step-back technique. Figure 13A is a longitudinal cross-sectional view of a tooth being cleaned with a file instrument used in the step-back technique. Figure 13B is a longitudinal cross-sectional view of the tooth shown in Figure 4A taken along cutting line 13B--13B, which shows the portion of the root canal which cannot be viewed in vivo. Figure 14A is a longitudinal cross-sectional view of a tooth depicting apical perforation during cleaning of the root canal. Figure 14B is a longitudinal cross-sectional view of a tooth depicting ledging during cleaning of the root canal. Figure 15 A is a transverse cross-sectional view of a tooth depicting a root canal cleaned by a prior art technique that has resulted in over thinning of the root canal. Figure 15B is a transverse cross-sectional view of a tooth depicting a root canal cleaned by a prior art technique that has resulted in lateral perforation. Figure 15C is a transverse cross-sectional view of a tooth depicting a root canal cleaned by a prior art technique that has resulted in over thinning of the root canal. Figure 15D is a transverse cross-sectional view of a tooth depicting a root canal cleaned by a prior art technique that has resulted in over thinning of the root canal. Figure 15E is a transverse cross-sectional view of a tooth depicting a root canal cleaned by a prior art technique that has resulted in over thinning of the root canal. Figure 16A is a perspective view of a set of endodontic instruments for cleaning of the coronal portion and operative middle portion of a root canal. Figure 16B is an enlarged perspective view of a tip of one of the files of an endodontic file instrument shown in Figure 16A. Figure 17A is a perspective view of another embodiment of a set of endodontic instruments for cleaning of the coronal portion and operative middle porttion of a root canal. Figure 17B is an enlarged perspective view of a tip of one of the files of an endodontic file instrument shown in Figure 17A. Figure 18 A is a perspective view of another embodiment of a set of endodontic instruments for cleaning of the coronal portion and operative middle porttion of a root canal. Figure 18B is a perspective view of another embodiment of a set of endodontic instruments for cleaning of the coronal portion and operative middle portion of a root canal. Figure 18C is another embodiment of a file tip of an endodontic file instrument shown in Figure 18B. Figure 19A is a longitudinal view of a tooth with an exposed pulp chamber. Figure 19B is a longitudinal cross-sectional view of of the tooth shown in Figure 19 A with a file portion of a file instrument 200a inserted into the root canal up to the apical portion. Figure 19C is a longitudinal cross-sectional view of the tooth shown in Figure 19B taken along cutting line 19C— 19C to depict the cleaning of the pulp material from the operative middle portion of the root canal. Figure 19D is a longitudinal cross-sectional view of a tooth with a file portion of a file instrument 220a inserted into the root canal up to the apical portion and being moved by a handpiece. Figure 19E is a longitudinal cross-sectional view of the tooth shown in Figure 19D taken along cutting line 19E— 19E to depict the file instrument 220d being moved by a handpiece to clean the pulp material from the operative middle portion of the root canal. Figure 19F is a longitudinal cross-sectional view of the tooth shown in Figures 19A-C depicting a coronal portion and an operative middle portion of a root canal which have been cleaned by the removal of the pulp material. Figure 19G is a longitudinal cross-sectional view of the tooth shown in Figure 19F to show that essentially all pulp material has been removed from the coronal portion and the operative middle portion of the root canal. Figure 20 A is a depiction of a practitioner employing an endodontic irrigation tip to demonstrate the convenience of employing the angled tip. Figure 20B is a view of a cross section of a tooth with the apical root portion being irrigated by the endodontic irrigation tip shown in Figure 20B. Figure 21 is a perspective view of an optional set of endodontic instruments for improving the access into the apical portion of a root canal. Figure 22 is a perspective view of an optional set of endodontic instruments for cleaning the apical portion of a root canal. Figure 23 is a perspective view of another embodiment of an optional set of endodontic instruments for cleaning the apical portion of a root canal. Figure 24 is a perspective view of an additional embodiment of an optional set of endodontic instruments for cleaning the apical portion of a root canal. Figure 25 is a longitudinal cross-sectional view of a tooth with a file inserted into a root canal having a length that is sufficient to reach the apex. Figure 26A is a longitudinal cross-sectional view of a tooth with a root canal that has been cleaned. Figure 26B is a longitudinal cross-sectional view of the tooth shown in Figure 26A taken along cutting line 26B— 26B to show that essentially all pulp material has been removed from the root canal. Figure 26C is an enlarged transverse cross-sectional view of the tooth shown in Figure 26 A taken along cutting line 26C—26C to show that the anatomy of the root canal has not been substantially altered by the cleaning thereof and to show the shaping of the canal in preparation of filling the root canal. Figures 27A-J are transverse cross-sectional views of endodontic files. Figure 28 is a longitudinal cross-sectional view of a tooth with a root canal being cleaned with a file instrument having a file formed by machining a groove into a metal blank. Figure 29 is a perspective view of another embodiment of an endodontic instrument. Figure 30 is a partial perspective view of an endodontic file depicting the tip of the file. Figure 31 is a partial perspective view of an endodontic file depicting the tip of the file. Figure 32 is a partial perspective view of an endodontic file depicting the tip of the file. Figure 33 is a partial perspective view of an endodontic file depicting the tip of the file. Figures 34A is an enlarged perspective view of x-ray image of a root canal of a vital tooth without periapical rarefaction. Figures 34B is an enlarged perspective view of an x-ray image of a root canal of an infected root canal without periapical rarefaction. Figures 34C is an enlarged perspective view of an x-ray image of a root canal of an infected root canal with apical and periapical resoφtion. Figure 35 is a view of a system of endodontic tools including a first set of instruments for cleaning the operative middle portion of an operative root canal, an optional second set of instruments for improving the access into the apical root portion and an optional third set of instruments for cleaning the apical root portion. Figure 36A is a cross-sectional view of a tooth after the pulp chamber has been accessed and before rectification. Figure 36B is a cross-sectional view of the tooth shown in Figure 36A after rectification and after the operative middle portion has been cleaned. Figure 36C is a cross-sectional view of the tooth shown in Figure 36 A after the apical portion has been widened. Figure 36D is a cross-sectional view of the tooth shown in Figure 36A after the apical portion has been cleaned. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to systems and methods for cleaning root canals through the removal of pulp material from the root canals. The invention provides for cleaning the root canal in progressive sections from crown to apex. After the pulp chamber is opened and preferably after further preparations, a first instrument or set of instruments is introduced into the root canal to clean the root canal up to the apical root portion. The apical portion is then cleaned by various alternative methods. The apical portion is preferably cleaned by deliverying an irrigant into the apical portion and then removing the irrigant along with any debris. In some instances, a second instrument or set of instruments may be optionally introduced to improve the access into the apical portion for introduction of a cannula of an irrigation tip. Alternatively, the apical root portion may also be cleaned with a third instrument or set of instruments. The invention enables a dental practitioner to remove and clean essentially all the pulp material in a root canal requiring root canal therapy. The cleaning is achieved in a manner that is safer in terms of over thinning of the root canal and perforations and yet requires less instrumentation than conventional techniques. The techniques described herein for progressive root canal therapy, from crown to apex, are essentially divided into distinct phases. The phases generally correspond with the particular sections or portions of the operative root canal. After the pulp chamber has been opened to expose the anatomical root canal, during the root canal therapy, as shown in Figure 18, the operative root canal is considered to include the anatomical root canal, which extends from the pulp chamber or the floor 256 of the pulp chamber 246 to the apex 254, and the operative coronal portion thereabove. More specifically, the operative root canal comprises the operative coronal portion 260, the operative middle portion 262 and the apical portion 264. Operative coronal portion 260 essentially includes the access cavity walls. The operative middle portion 262 is the upper portion of the anatomical root canal while the apical portion 264 is the lower portion of the anatomical root canal. The divisions of the operative root canal are distinguished from the nomenclature of the anatomical root canal as used to designate the sections before opening the tooth wherein the anatomical root canal is divided into the apical portion and the coronal portion. The coronal portion of the anatomical root portion is conventionally defined as the upper portion of the anatomical root canal which terminates at the floor of the pulp chamber. However, once the pulp chamber is exposed and instruments are introduced into the root canal, the opening into the tooth should be treated as an extension of the operative root canal as it is then a continuous chamber or open tract. Accordingly, the access walls are considered part of the operative root canal and are designated as the operative coronal portion or the access portion. Apical portion 264 extends from the apex of root canal 252 up to an area of anatomical root canal 252, such that the length of the apical portion is less than half of the length of the anatomical root canal as measured from the apex to floor 256. More specifically, apical portion 264 is generally the bottom one-half of the anatomical root canal 252. The actual length of the apical portion varies depending on many factors such as the type of tooth and the age of the tooth. However, the apical portion typically has a length in a range from about 3 mm to about 4 mm as measured from the apex. As also indicated hereinabove, operative middle portion 262 is the top portion of the anatomical root canal 252 and extends from floor 256 down to an area of anatomical root canal 252, such that the length of the operative middle portion is greater than half of the length of anatomical root canal 252. More specifically, operative middle portion 262 is generally the top two-thirds of anatomical root canal 252 as measured down from floor 256. The length of operative middle portion can be estimated by identifying the overall length of the root canal, typically by use of radiography, and then subtracting about 3 mm to about 4 mm from the overall length. As previously indicated, the three sections are treated in primarily distinct sequential phases including: preparation of the operative coronal portion, then cleaning or preparation of the operative middle portion, optionally improving access to the apical root portion and finally cleaning of the apical portion preferably by just irrigating the apical portion or alternatively by use of abrasive instrumentation. Examples of instruments intended for use in the cleaning the operative middle portion are shown in Figure 16A and Figure 17B. Figure 37A and Figure 20B depict insertion of a cannula of an endodontic irrigation tip into a root canal to deliver irrigants. Figure 21 depicts an example of a set of optional instruments designed for use in improving the access to the apical root portion. Examples of optional instruments intended for use in cleaning the apical portion in an abrasive manner are shown in Figures 22-24. The first phase or coronal phase involves exposing the pulp chamber and also preferably other steps to enhance accessibility into operative middle portion 262 and also apical portion 264. Accordingly, the coronal or access phase is initiated by removing the top of the chamber to expose the pulp chamber. This can be achieved, for example, through the use of an instrument such as instrument 120 with bur 122 as shown in Figures 11 A and Figure 1 IB, which is preferably a diamond bur used in conjunction with a low or high speed handpiece. However, any suitable instrument can be utilized. After the pulp chamber has been exposed and after the pulp material has been removed, a tooth appears as shown in Figure 19A wherein a molar 240 is depicted with the overhanging portions of enamel 242 and dentin 244 removed to provide access into pulp chamber 246. Pulp material 250 still extends within root canal 252 from apices 254a and 254b to the floor 256 of pulp chamber 246. Also designated at 248 is the cementum of the tooth. During the first phase, it is preferable to remove or reduce dentinal or enamel protrusion or irregularities that may obscure or hinder access of instruments into the remaining portions of the operative root canal. For example, dentinal shelves 266 depicted in Figure 19A are preferably reduced or rectified to provide greater access for instrumentation during the subsequent phases. More particularly, interferences are preferably removed or minimized such that instruments can be inserted in the anatomical root canal in a relatively straight manner. Accordingly, in the subsequent related drawings, such as Figure 19B, the dentinal shelf is shown removed on the canal being cleaned and as not being yet removed above the other canal. Rectification or regularization can be achieved by any suitable means. It may also be necessary to widen the tract of the operative coronal root canal. Some dentists may prefer to obtain greater access through a cuspidectomy. Note that during the root canal procedure procedure, a rubber dam is typically used to isolate the tooth, which may require in some instances, the rebuilding of the pulp chamber walls. During this phase as well as the others, it is generally necessary to inigate the root canal with irrigants or a root canal conditioner/lubricant. After the operative coronal portion has been adequately prepared, it is preferable to prepare an x-ray image of the tooth to identify the length of the operative root canal in order to determine the prefened working length for the instrument or set of instruments to be used in the next phase. The prefened working length is preferably identified by subtracting about 3 mm from the total radiographic length of the operative root canal. The total radiographic length is preferably derived from a radiograph made using a localizator and a long cone radiographic head. The second phase involves cleaning or preparation of operative middle portion 262. It may also involve to some extent further rectification of the operative coronal or access portion 260 through further removal of any ledges or outcroppings which prevent straight and easy access into the operative middle portion 262. Additionally, it may also involve some degree of rectification of the upper region or segment of operative middle portion 262. An example of a set of instruments designed for cleaning the operative middle portion is shown in Figure 16A. The set comprises three file instruments 200 which each comprise a handle 202 connected to a file 204 or a shaft with tines or an abrading portion. Each file 204 has a top end 203 where the file joins handle 202. Handle 202 is connected to top end 203 of file 204 such that movement of handle 202 also moves at least top end 203 of file 204 along a common longitudinal axis with handle 202. The diameter of top end 203a is less than the diameter of top end 203b and the diameter of top end 203b is less than the diameter of top end 203c. When utilized to clean the operative middle portion of a root canal, file 200a is first introduced into the operative middle portion followed by file instrument 200b and then 200c. Accordingly, the diameter of the top end of each successive file introduced into the operative middle portion is greater than the diameter of the top end of each preceding file. Each file terminates at a tip 208 located opposite top end 203. The diameter of each tip 208 in a set of instruments is essentially the same such that the diameter of tip 208a is about the same as the diameter of tip 208b and tip 208c. For example, a set of instruments may all have tip diameters of about JO mm. A set may also be designed such that the instrument intended to be inserted first has a tip diameter of about JO mm while the other instruments in the set have a tip diameter of about J3mm. A set with slightly different tip diameters, such as a set of three or four instruments with respective tip diameters of J 0 mm, .10 mm, .13 mm and .13 mm, and in any event not exceeding 0J5 mm, is still considered to have substantially constant tip diameters within the set as the difference in size is very minor and the diameters do not sequentially increase for each instrument. In an alternative embodiment, the tip diameter may vary between instruments in a set such that, for example, the tip diameter of each sequentially inserted file is progressively larger. As shown in Figure 16B, which is an enlarged view of tip 208b, the tips are generally shaφ and are configured for at least minimal cutting capability. Each operative middle portion file 204 is configured with a suitable abrading portion 209 along most or all of the length of each file. The file is preferably configured such that the abrading portion 209 extends along its entire length as shown in Figure 16 A, however, the files may also have a smooth upper shank portion. Abrading portion 209 is at least the outer edge of the file 204. The abrading portion of the files in Figure 16A are formed by twisting a blank such as a rectangular blank. Figure 17A depicts another set of file instruments 210 which have files with a different abrading portion compared to the abrading portion of the files of file instruments 200. The files 214 have abrading portions 219 that were formed by machining the files to have knurled surfaces. Abrading portion 219 as well as abrading portion 209 and the other abrading or cleaning surfaces disclosed herein are examples of means for abrading the walls of the root canal or root canal surfaces. Figure 17B is an enlarged view of tip 218a which is shown with a more rounded configuration than tip 208b such that the tip has essentially no cutting capability. Figure 18B shows another embodiment of a suitable tip which is designed for more aggressive cutting than tip 208b at least as the tip is pushed downward. Since the tip diameters are essentially equal and since the diameter of the top end of each successive file introduced into the operative middle portion is larger than the diameter of the top end of the preceding file, the taper of each successive file in the set is larger than the preceding file. For example, the taper may range from .04 to .13 and increase in increments for each successive file. Each successive file accordingly has an increased surface area for cleaning the root canal. Additionally, as files are inserted into a root canal with larger and larger tapers, the rigidity of the upper half of each successive file also increases. The increase in rigidity is, however, minimized by maintaining the tip of each file at about the same diameter. The flexibility of the lower half remains essentially constant. The rigidity in the upper half is used to remove interferences and to properly rectify the operative coronal portion 260 and the operative middle portion 262. The consistency in rigidity at the upper half is useful since the lateral perimetrical force applied to the handle is primarily transfened to its upper half or at least the part closest to the handle, which is the strongest part of the file. By properly selecting a combination of factors including the diameters of the files at the top ends and at the tips as well as the material used to form the files, the files are designed such that each file has sufficient flexibility to be flexed or curved to urge the abrading portion against the surfaces or walls of the root canal and sufficient rigidity to apply pressure against the surfaces of the root canal as the abrading portion of the file is urged against the surfaces of the root canal and simultaneously moved in a cleaning motion. Additionally, the files have adequate resilience to avoid being substantially deformed as the file instrument is flexed or curved to urge the abrading portion against the surfaces of the root canal. The file can be formed from any suitable material. In forming a suitable file, the material is preferably selected in view of the dimensions and design, to yield a file having the desired properties with respect to flexibility, resilience and/or rigidity as set forth above. The prefened material for forming files used to clean the operative middle portion of root canals is stainless steel. Other metals can also be used such as nickel/titanium; however, it may be necessary to design the files to have larger diameters than files formed from stainless steel when using nickel/titanium as nickel/titanium tends to be more flexible than steel. Alternatively, the files can be formed from suitable non-metal materials, such as a plastic. When the files are formed from stainless steel or a material with comparable properties, the top end diameter of each file, where the abrading portion terminates, may range from about .25 mm to about 2 mm. However, the diameter will more typically range from about .3 mm to about 1.8 mm and most typically from about .4 mm to about 1.5 mm. Additionally, when the files are formed from stainless steel or a material with comparable properties, the tip diameter of each file may range from about .06 mm to about .4 mm. More typically, however, the tip diameter will range from about .08 mm to about .15 mm and most typically from about .08 mm to about A mm. The length of each file in the set used to clean the operative middle portion depends on the length of the tooth being cleaned. More particularly, after identifying the length of the root canal from an x-ray image, the length of the file to be used in the operative middle portion is determined by subtracting 3 mm from this identified length of the root canal. This length is typically between about 15 and about 20 mm, however, longer files, such as a 25 mm long file, are typically required for canine teeth. To provide for the different root canal configurations which may be encountered, it is prefened to have files with lengths ranging from about 8 mm to about 35 mm. However, files with lengths ranging from about 10 mm to about 30 mm will be most utilized and files with lengths ranging from about 14 mm to about 26 mm will be the most frequently utilized. After identifying the combined length of the operative middle portion and the operative coronal portion and after removing the overhanging enamel 242 and dentin 244, the practitioner selects a file instrument or a set of file instruments as shown in Figure 16A or Figure 17A with an appropriate file length. In an embodiment that utilizes no stops, the appropriate length conesponds to the combined length of the operative middle portion length and the operative coronal portion. As shown in Figure 19B, file 204a of file instrument 200a is then inserted into root canal 252 down through operative middle portion 262 without extending substantially into apical portion 264. Each file 204 of each file instrument 200 in the set of instruments shown in Figure 16A has a length that is only sufficient to enable the file to contact the operative middle portion and the operative coronal portion of the root canal. Accordingly, a file instrument such as file instrument 200a or a set of file instruments such as 200a, 200b and 200c comprises a first endodontic instrument means for anatomically removing and anatomically cleaning essentially all pulp material from the operative middle portion without significantly extending into the apical root portion. The file length of files 204 enables a practitioner to aggressively clean the operative middle portion without worrying that the instrument will overly thin the root canal, perforate the apex or that cleaning will cause extrusion of material through the apex. Another benefit of cleaning the operative middle portion first is that the apical portion is then generally more accessible and easily cleaned. Additionally, since instruments are selected for use in cleaning the operative middle portion which have files lengths that do not permit entry into the apical portion, the likelihood of jamming or breaking a tip of an instrument while working in the confined space of the apical portion is prevented. By instrumenting in the operative middle portion and the operative coronal portion before the cleaning the apical portion, the practitioner can use an instrument that is relatively flexible compared to the conventional instruments. As shown in Figure 19C, which is a cross-sectional view taken along cutting line 19C--19C of tooth 240 in Figure 19B, file 204a of file instrument 200a is sufficiently flexible to be flexed against any surface of operative middle portion 262 or operative coronal portion 260 and yet is sufficiently rigid to remain flexed against the surface during a cleaning motion such as a longitudinal motion, a rotational motion or a reciprocating rotational motion. The file is also sufficiently resilient that substantial deformation of the file does not occur due to the forces experienced during cleaning of the pulp material from the root canal. File instrument 200a is shown in Figures 19B and 19C being moved in a longitudinal movement or up and down movement as well as being rotated while file 204a is flexed or arched to urge the file against the root canal surfaces. As shown, the configuration of the files used to clean the operative middle portion, and preferably the operative coronal portion as well, enable a practitioner to move the files around the perimeter or from side to side to contact the perimeter. Further, since the file is moved around the perimeter, the file has more than one center of motion during cleaning of the operative middle portion of the root canal, such as a pivot point or center of rotation, as the tip of the file or at least a part of the abrading portion does not generally remain primarily in one position. This is in shaφ contrast to prior art methods which limited the practitioner to essentially rotating a conically shaped file to yield a cone shaped borehole. Due mainly to the configuration of the files, each file is able to flex such that its abrading portion is urged against root canal surfaces while the instrument is rotated and moved in a cleaning motion. Accordingly, the contours of the operative coronal portion and the operative middle portion can be used during their cleaning by a practitioner as a guide for the movements of the instruments as the files are pushed against the surfaces of the root canal and simultaneously moved around the perimeter or periphery of the root canal until the practitioner has reached the beginning location of the cleaning and shaping process. For example, in root canals that are primarily noncircular, the files can be urged along one side and then along the next side wall in a manner such that the resulting cleaned and shaped root canal is generally widened but still primarily noncircular. In other words, there is essentially no borehole that obviously conesponds to the shape of the file as the instruments have been moved in conformance to the anatomical shape of the operative middle portion. Due to the ability to move the file as discussed, the anatomy of the root canal remains substantially unaltered despite the cleaning of essentially all pulp material from the operative middle portion. The understanding that the final anatomy is guided by the shape of the original anatomy enables a practitioner to more confidently urge a file such as file 204a against all surfaces of root canal 252 and aggressively clean all of the surfaces of operative middle portion of the root canal since the likelihood of overly thinning the root canal or causing lateral perforations as shown in Figure 15A-C and Figure 15E is diminished. The assurance of the safety of the methodology is further bolstered by a general knowledge of wall thickness variations. Another advantage of the configuration of operative middle portion instruments, such as file 204a shown in Figures 19B and 19C, is that the file can simultaneously abrade both operative coronal portion 260 and operative middle portion 262. The files can simultaneously abrade both portions as each file has an abrading portion along the entire length of the file. A primary benefit of simultaneously abrading both portions is the ability to further straighten the operative coronal portion while cleaning the operative middle portion. Use of files in the operative middle portion which have an abrading portion along their entire length is in contrast to files formed in accordance with ISO standardization. ISO standardized files have abrading portions of up to 16 mm and the remainder of the file is a smooth shank. Examples of such files are shown in Figures 13A-B and 14A-B. Since such conventional files are inserted down to the apex, it is generally not possible to abrade any portion beyond the anatomical root canal. Since such conventional files frequently fail to remove interferences extending from the access or root chamber above the anatomical root canal, as shown in Figure 13 A, the instrument must bend around the interferences, thereby further increasing the likelihood of wall perforations, overthinning and failing to clean significant portions of the canal. It especially increases the likelihood of iatrogenic modifications resulting from the tip of the file. The instruments in the sets shown respectively in Figure 17A and in Figure 18 A at 210a-c and at 220a-d are each depicted with a stop 140. Stops such as stop 140 may be used to ensure that the length of the portion of the file inserted into the tooth is such that the file does not extend significantly into the apical root portion. Figure 19D depicts the use of stop 140 on instrument 220a. The advantage of using such a stop is that less sets of instruments are needed in order to have a set that can be utilized in teeth of varying lengths. Note that while stops are shown which have a thickness of about 1 mm, the stops may have varying thickness. Also, the stops may also be positioned such that one or more stops are positioned adjacent to the handle such that movement is not possible since the stops already abut the handle. For example, in Figure 18A two stops are positioned on shank portion 226a of file 224a. One of the stops has a thickness of 2 mm while the other has a thickness of of 1 mm as shown respectively at 141 and 140. Note that stop 141 abuts handle 222a to prevent any possible movement. All of the stop disclosed herein are examples of stop means for limiting the operative middle portion instrument means to insertion into the operative coronal portion and the operative middle portion. When a stop is used, the length of the root canal from an x-ray image is first identified and then the length of the root canal above the apical root portion is determined by subtracting 3 mm from this identified length of the root canal. An instrument is then selected that has a length that is slightly longer than the determined length of the root canal down to the apical portion. Note that this determined length is the combined length of the coronal portion and the operative middle portion. It may also be advantageous to use a stop such as stop 140 to more easily flex the file against the root canal surfaces. More particularly, using an instrument with a stop alters the curvature of the file since the portion above the file is also flexed. This results in a different flexed configuration or pivot point so that greatest pressure is applied at a higher part of the root canal than when an instrument is used without stops. The desirability of applying pressure in such a manner depends on the particular tooth. Note however that if an instrument is used without a stop as in Figure 19B and Figure 19C the portion of the file that is flexed against the root canal can also be used to abrade sections thereabove by merely moving the file upward as it is flexed. Although the file instruments used to clean the operative middle portion, can be manually moved, they are preferably used in conjunction with an instrument designed for movement of endodontic file instruments such as a conventional dental handpiece instrument. The handpiece 500 shown in Figure 19D and in Figure 19E at 500 corresponds with the handpieces disclosed in Serial No. 09/425,849 and Serial No. 09/425,857. Handpiece 500 has a head 600 with a head element 610 that holds a chuck 700. One of the advantages of handpiece 500 is that rim 614 of head element 610 is essentially coplanar with any bottom surfaces of head element 610. This essentially coplanar configuration is particularly useful since rim 614 is used as a stop as it is rested on the coronal surface of tooth 240'. The ability to use rim 614 as a stop eliminates the need for rubber stoppers. Although, it is not necessary to use a stop when using instruments adapted for use with the handpiece disclosed in the above-identified applications, a stop is shown being used in Figure 19D in order to illustrate the use of stops with handpieces in general. Accordingly, it is understood that the instruments disclosed herein can be used with any conventional handpiece. When rotated by a handpiece, the file instrument such as instrument 220a shown in Figure 19D can be continuously rotated in one direction only or the file instrument can be rotated in a reciprocating motion such that the file instrument rotates for example, clockwise for half of a revolution and then counterclockwise for half a revolution. A reciprocating motion is preferred as such motion enables the file to alternately engage material 250 and the walls of the operative middle portion of the root canal in a manner that removes material 250 and to then rotate in the opposite direction such that the file less aggressively engages material 250 and the operative middle portion walls, depending on the file design. Accordingly, rotating file instrument 220a in a reciprocating motion minimizes breakage of file 224a when file 224a encounters a surface that prevents rotation of file instrument 220a in a direction that enables cleaning and removal of material 250. Handles 202a-c, 212a-c, and 222a-d are latch-type handles designed for coupling with a handpiece. Note that although instrument 200a has a latch-type handle, a handpiece is not depicted in Figure 19B and Figure 19C being used to move the file instrument, in order to optimally view the movement of the instrument. An example of a handle adapted for manual manipulation is shown in Figure 28 at 312. Movement of the file instrument with a handpiece is prefened as hand milling is more difficult and time consuming. A file instrument can also be vibrated to clean the coronal portion and the operative middle portion. File instrument 220a shown being utilized in cleaning the coronal portion 260 and the operative middle portion 262 of tooth 240' in Figure 19D is part of a set of instruments depicted in Figure 18 A at 220a-d. File instruments 220a-c have the same dimensions as instruments 200a-c and are similarly configured except that each of file instruments 220a-c has a shank portion 226. The shank portions 226a-d at respective top ends 223a-d provide for easy movement of stops 140. As previously indicated in reference to the set of instruments depicted in Figure 16A at 200a-c, the instruments used to clean the coronal portion and the operative middle portion may be configured without a smooth shank portion. If the instruments have a shank portion it is preferably about 2 to about 4 mm in length and is preferably about 4 mm. Note that the instruments in Figure 17 A depict relatively short shank portions that are about 2 mm in length while the instruments in Figure 18A depict longer shank portion that are about 4 mm in length. The shank portions depicted in Figure 17 A, Figure 18 A, Figures 18C have a slight taper; however, the shank portions may also be non-tapered like the shank portions of the instruments shown in Figure 23 and in Figure 24. The set of instruments shown in Figure 18A also includes an aggresive abrasion instrument 220d. After the operative coronal portion and the operative middle portion have been cleaned and shaped through the use of instruments such as abrasion instruments 220a-c then the root canal can be more aggresively shaped with instrument 220d. Like the other instruments in the set, instrument 220d has a file 224d with a shank portion 226d at its top end 223d; however, the file 224d has a unique abrading portion 229d. File 224d, more particularly abrading portion 229d, has an abrasive upper section 225d for aggresive abrasion and a lower section 227d that is relatively less abrasive than the upper section. The upper section 225d has abrasive particles positioned thereon while the lower section 227d is not coated with abrasive particles but is twisted or fluted. File 224d is formed by twisting the lower section and positioning an abrasive on part of the smooth or non-fluted upper section of the file above the lower fluted section. All of the smooth or non-fluted upper section may be coated so that there is no shank portion or a portion may be left uncoated so that there is shank portion as shown in Figure 18A at 226d. The advantage of using an instrument with a file having an upper section with abrasive particles such as instrument 220d as shown in Figure 18 A or instrument 220d' as shown in Figure 18B is that the coronal portion and the top of the operative middle portion can be more aggresively shaped while shaping the bottom of the operative middle portion less aggresively. The usefulness of an instrument such as instrument 220d to clean or shape with greater abrasiveness at its upper half and less abrasiveness at its lower half is depicted in Figure 19E which is a cross-sectional view of tooth 240' with instrument 220d being moved by chuck 700 of endodontic handpiece head 600. The upper abrasive particle coated section 225 d enables the removal or reduction of dentinal or enamel protrusions or inegularities such as dentinal shelves shown at 266 in Figure 19D that may obscure or hinder access of instruments into the operative root canal. In many instances, use of an instrument such as instrument 220d eliminates the need for rectification of such protrusions with a rectification instrument. Note that tooth 240' shown in Figure 19E is nearly identical to tooth 240 shown in Figure 19C, the only difference is that tooth 240' does not have an outcropping of dentin to divide the canal like that identified as 244 in Figure 19C. Tooth 240' appears without such an outcropping to clearly illustrate that the depicted movements of the instruments in Figure 19C and in Figure 19E occur in accordance with the present invention in the operative middle portion of all teeth. Stated otherwise, such movements enable the file to follow the contours of the root canal and are utilized in the operative middle portion of all root canals. The abrasive particles are preferably diamonds. The application, impregnating, coating or attachment of the diamond coating may be achieved by any conventional method. For example, the abrasive particles may be electrolytically applied, plated, sintered, bonded with adhesives or impregnated into the surface of the smooth part of the file. Examples of prefened methods of positioning abrasive particles includes forming the coating by electro-deposition or by direct or indirect sputtering. Although, diamond is the prefened material other materials may be optionally used instead of or in addition to diamond. Examples of suitable materials for use as abrasive particles include: carborundum™ or other suitable refractories of silicon carbide, fused alumina and other materials; aluminum oxide; natural aluminum oxide such as corundum; alumina ceramics; glass; silicon dioxide or silica; silicon carbide; boron nitride; and other comparably hard materials. The abrasive particles may form a coating, layer or covering with any suitable thickness and the particles may have any suitable average size. More particularly, the thickness of the abrasive particle coating is preferably in a range from about 100 μm to about 700 μm, more preferably about 200 μm, and most preferably about 500 μm. A prefened average particle size is in a range from about 30 μm to about 350 μm. A more preferred average particle size is in a range from about 50 μm to about 250 μm. Files with abrasive particle coated upper sections also preferably have a smooth shank portion below the handle. The smooth shank portion preferably has a length of about 2-4 mm. The upper abrasive particle coated section is preferably no greater than about half of the length of the file extending from the handle and is more preferably less than half of the length of the file extending from the handle. Instruments having an abrading portion with an upper abrasive particle coated section and a lower less abrasive section are preferably configured such that the length of the upper abrasive particle coated section is about the same as the lower less abrasive section. The lengths of such upper abrasive particle coated sections are accordingly in a range from about 4 to about 10 mm in length and are preferably in a range from about 4 to about 8 mm in length. Lower fluted section 227d is an example of a lower less abrasive section. The lower less abrasive section may also be configured like the knurled surface of abrading portions 219 or any other surface which abrades less aggresively than the use of abrasive particles. The lower section may also alternatively be smooth like the shank portion and terminate at a tip so that it has essentially no abrasive ability. The file of the instrument preferably has the abrasive particle coating on only the upper section of its abrading portion as shown in Figure 18 A, Figure 18B and in Figure 19E; however in some embodiments, the entire abrading portion may be coated with abrasives. Additionally, the upper section that has abrasive particles may also be twisted or fluted as shown in Figure 27J so that the entire abrading portion is twisted or fluted while only the upper section is covered with abrasive particles. Similarly, the entire abrasive portion may be configured as shown in Figure 17A with a knurled surface while the upper section is covered with abrasive particles. Further, the abrading portion may have any appropriate configuration and have an upper portion with abrasive particles that enable more aggresive abrasion in the operative coronal portion of the root canal and in the top region or segment of the operative middle portion of the root canal. An instrument such as instrument 220d or 220d' is preferably part of a set of instruments such as the sets shown in Figure 18 A or 18B such that the set includes at least one abrasion instrument and one aggresive abrasion instrument. The set of instruments shown in Figure 18B includes only the last two instruments of the set shown in Figure 18 A. Note that the only difference depicted between instrument 220d and instrument 220d' is that instrument 220d has a smooth tip 228d for less aggresive cutting while instrument 220d' has a pointed tip 228d'. Pointed tip 228d is shown in greater detail in Figure 18C. Advantages of using a set such as instruments 220c-d' instead of a larger set such as instruments 220a-d is that the set is less expensive and is simpler to use. However, it may also be preferable to use a set with three, four or more instruments to clean the operative coronal portion and the operative middle portion with very gradual increases in rigidity so that the aggresiveness of the abrading is gradually increased as the instruments are sequentially utilized. As indicated above, while instruments 220a-c have shank portions these instruments have the exact same dimensions as instruments 200a-c. Accordingly, the files of instruments 220a-c all have essentially the same length and tip diameter and also have sequentially larger top end diameters and tapers. Aggresive abrasion instruments 220d and 220d', however, are each shown with a file having a length, tip diameter, top end diameter and taper that is essentially the same as that of file 224c. Although, the file of the aggresive abrasion instrument preferably has the same dimensions as the instrument previously inserted into the root canal, other configurations may also be utilized. For example, the aggresive abrasion instrument may have a larger top end diameter and a larger taper than the file of the instrument introduced previously in the sequence or a smaller top end diameter and a smaller taper. Instruments such as instruments 220d or 220d' may be used alone or as part of a set to remove and clean essentially all pulp material from the operative coronal portion and the operative middle portion. Instruments such as 220d or 220d' as well as sets that includes such instruments are additional examples of first endodontic instrument means for anatomically removing and anatomically cleaning essentially all pulp material from the operative middle portion without significantly extending into the apical root portion. Figure 19F shows a cross-sectional view corresponding to the x-ray view after pulp material 250 has been removed from the operative middle portion 262 of root canal 252a and after the surfaces of root canal 252a have been shaped to yield shaped surfaces 268a of the root canal. Figure 19G is a longitudinal cross-sectional view taken along cutting line 19G--19G of tooth 240 in Figure 19F which clearly shows that essentially all pulp material has been removed and cleaned from operative middle portion 262. Removal of pulp material 250 from operative middle portion 262 removes the majority of bacteria in the pulp canal since the majority of bacteria in an infected root canal is typically located in the operative middle portion. Not only is the greatest volume of bacteria in the operative middle portion but it is also believed that the concentration is greater in the operative middle portion. Since a certain minimum threshold must generally be reached for complications to arise due to microbial presence in a root canal, removal of the pulp material in the operative middle portion significantly reduces the likelihood of such complications. By removing the majority of bacteria before cleaning the apical portion there is also less likelihood of exposing the sunounding tissue to bacteria due to overly thinning the root canal, perforation or extrusion of material from the canal. The greatest likelihood for the occurrence of complications such as over thinning of root canal walls, perforation or extrusion of material from the canal is in the apical portion. The apical portion is the most likely site for such complications as apical portions are more complex and delicate compared to the operative middle portions of teeth. Since such complications are most likely to occur in the apical portion, it is highly beneficial to have the material removed from the operative middle portion in order to minimize the amount of material that can come out of the root canal to cause problems. For example, in the event of an apical extrusion far less septic material may be expressed during instrumentation in accordance with present methodology than if the apical extrusion occcured as a result of cleaning in accordance with conventional methods wherein files are inserted to the apical portion before cleaning the operative middle portion. As a result, removal of the majority of bacteria before cleaning the apical portion increases the likelihood of successful root canal therapy in several ways compared with conventional methods. To minimize the possible introduction of bacteria, it is preferable to utilize a kit. The kits preferably support a set of several instruments with identical lengths positioned to be easily grasped and preferably in an antimicrobial solution. It should be noted that when there is an atresic root canal, it is preferable to use EDTA in a hydrosoluble gel and leave the composition in the canal for a few minutes. Similarly, for necrotic canals, it is advisable to work in a sodium hypochlorite saturated environment. For canals with living pulp, it is advisable to work in an environment saturated with 10% hydrogen peroxide. As previously discussed, the majority of bacteria in an infected root canal is typically located in the operative middle portion. Accordingly, it has been found that after the operative middle portion has been cleaned in an abrasive manner effective root canal procedures are completed by cleaning the apical portion without abrading the apical portion. More particuarly, after removing and cleaning essentially all pulp material from the operative middle portion of an operative root canal in conformance with the anatomical shape of the operative middle portion by flexibly moving an instrument within the operative middle portion, the root canal procedure can be effectively completed by merely irrigating the apical portion of the root canal and then removing the irrigant and debris. This eliminates the possibility of exposing the sunounding tissue to bacteria due to overly thinning or perforating the apical portion of the root canal and minimizes the possibility of extrusion of material from the canal. Since such complications typically occur during abrasive instrumentation within the apical portion due to the delicate and complex structure of the apical portion, the elimination of the need for abrasive instrumentation in the apical portion is highly advantageous. Further, this methodology is particularly advantageous in light of the prior cleaning of the root canal above the apical portion. Another benefit of cleaning the apical portion by irrigating the apical portion with an inigant and then removing the inigant and debris from the apical portion, is the reduction in the number of instruments needed to complete the procedure. More particularly, since instruments adapted for abrading the apical portion are not necessary but are optionally used, the total instruments used in performing root canal procedures is reduced. In addition to cleaning the apical portion, irrigation is used to maintain the smear layer in solution within the apical portion, thereby avoiding smear layer accumulation. Additionally, it is useful to maintain the debris derived from cleaning the root canal in suspension to avoid filling the apical portion of the root canal with a plug. If the apical portion becomes filled, there is an increased likelihood that the progression may be prevented or that debris may be pushed out of the tooth. In addition to conventional irrigation devices, a prefened irrigation device is shown in Figure 20A and Figure 20B which is a syringe 790 coupled to an irrigation tip 720. While such irrigation devices are prefened, any conventional inigation tip and associated delivery device such as a syringe may be utilized. Note that due to the angled configuration, as shown in Figure 20A and Figure 20B, a practitioner is readily able to place the cannula 760 extending from neck 740 of angled tip 720 into a root canal 782 of a patient's tooth 780 while holding a syringe 790 coupled to tip 720 at an angle with respect to the patient's mouth. This angled configuration enables the practitioner to more easily insert cannula or needle 760 into a root canal and to move the tip within the root canal. As shown, the practitioner is able to strategically, conveniently position stop end 744 on the rim of the occlusal surface of a crown and orient cannula 760 in a controlled manner within root canal 782. Note that neck 740 has a stop end 744 with a distal flat face 746 which is configured to act as an integral stop to prevent penetration into the root canal 782 of endodontic irrigator tip 720 beyond the length of the portion of cannula 760 extending from stop end 744 of neck 740. The working length of cannula 760 is the portion of cannula 760 extending past stop end 744 of neck 740. By using an irrigator tip having a cannula with the appropriate working length and a neck 740 having an integral stop end 744, the practitioner is able to avoid apical perforations. For example, as shown, a tip may be selected with a cannula length which extends within about 1 millimeter above the apex 784, while stop end 744 prevents cannula 760 from penetrating too far. This permits the calculated delivery of fluid all the way to apex 784 without perforating apex 784. Thus, because of stop end 744 and a cannula 760 having an appropriate working length, the practitioner can confidently place cannula 760 in close proximity to apex 784 without perforating apex 784. Note that it is prefened to slowly withdraw cannula 760 while deliverying the irrigant. Although, tip 720 is prefened, other conventional endodontic irrigator tips may also be utilized and conventional stops may also be utilized. Another prefened inigation tip is the Endo-Eze® inigator tip sold by Ultradent Products, Inc which has a straight cannula or needle. Examples of suitable Endo-Eze® irrigator tip include those which have a 27 gauge cannula (.40 mm out diameter), 30 gauge cannula (.30 mm outer diameter) and a 31 gauge (.25 mm outer diameter). In some circumstances, larger needles may be used. In any event, the needle or cannula is preferably sufficiently small to avoid binding within the cannula and also to enable backflow for flushing the apex. The inigator tips and other suitably shaped nanow tubular devices such as pipettes, are refened to herein as apical portion cleaning instruments. The irrigator tips disclosed herein and other suitably shaped narrow tubular devices, are examples of means for cleaning the apical root portion, after the pulp material has been essentially removed from the operative middle portion. More specifically, the inigator tips are examples of means for cleaning the apical root portion by deliverying an irrigant into the apical root portion. In addition to syringes, such irrigator tips may be coupled to a Stropko device. Syringes and the Stropko device are examples of delivery devices. These same devices are examples of irrigant delivery devices when coupled with an irrigator tip that enables the delivery devices to easily access the root canal. While these irrigant delivery devices are particularly useful when cleaning the apical portion, note that all of these irrigant delivery devices may also be used in irrigating the canal at any appropriate time during the root canal procedure. Note that syringes and other delivery devices such as a Stropko delivery device are examples of means for deliverying irrigants and/or removing irrigants and any remainig debris via the irrigator tip or means for cleaning the apical root portion. Pipettes are a less prefened alternative to the use of irrigation tips as apical portion cleaning instruments to deliver inigants into the root canal. Such conventional pipettes are well known in endodontistry and are used to deliver irrigants by squeezing part of the pipette. The pipettes may be prefilled or used with a separate reservoir or container of lubricant. A pipette is an example of an integral irrigant delivery device while an irrigator tip coupled to a syringe or a Stropko device is an example of a separable irrigant delivery device. Such integral irrigant delivery devices are additional examples of means for cleaning the apical root portion or more specifically, means for cleaning the apical root portion by deliverying an irrigant into the apical root portion. These same irrigant delivery devices are typically used to remove the irrigant and any remaining debris. For example, the syringe may be used to aspirate the inigant and any remaining debris out of the apical portion. Similarly, a pipette may apply appropriate suction to remove the irrigant and any remaining debris. The endodontic irrigator tip may also be coupled to other conventional aspiration devices. Other irrigant removal devices include conventional paper points. When the irrigant and debris have been removed, the tooth appears as shown in Figure 20B at 780. Although, the irrigant preferably is capable of dissolving or disrupting soft tissue remnants to permit their removal, the irrigant may be any suitable liquid such as water or various alcohols. More particularly, although some degree of debridement is prefened, any fluid may be used to flush debris from the root canal. General examples of appropriate irrigants include hydrogen peroxide, primarily for use in the canals of living teeth, or sodium hypochlorite, primarily for the canals in necrotic teeth. The preferred irrigant is the aqueous sodium hypochlorite solution sold as ChlorCid® by Ultradent Products, Inc which contains about 2.5-3% NaOCL. The irrigant may also be a chelator or calcium remover such as EDTA solutions or citric acid solutions. A prefened chelator is sold as File-Eze® by Ultradent Products Inc. which is a 19% EDTA water soluble viscous solution. File-Eze® is a prefened chelator as it is also a lubricant. Another example of a commercially available chelator is the Pulpdent EDTA solution sold by Pulpdent Inc. In some circumstances, it may be necessary to improve the access into the apical root portion before cleaning the apical root portion of the root canal. More particularly, it may be beneficial or necessary to widen the tract of the root canal to provide access for thin inigation needles. This may be achieved by widening the transition between the operative middle portion and the apical portion or by widening the entire apical portion such that a thin irrigation needle can access the apical portion as needed. Thin irrigation needles typically have a diameter no smaller than about .30 mm so it may be necessary to increase the diameter of portions of the root canal up to about .35 mm or even up to about .40 mm, particularly within the region of the boundary between the operative middle portion and the apical root portion. Note that the diameter need only be slightly larger than a thin irrigation needle in order to provide adequate access. Improving access into the apical portion not only enables such irrigation needes to have move as needed, it also reduces the likelihood that the thin inigation needes will be blocked. The diameters of many root canals within the region of the boundary between the operative middle portion and the apical root portion and even within the apical portion are alreadly large enough to enable irrigation needles to deliver irrigants as far as is necessary. However, even though it is prefened not to widen the diameter within the apical portions or even the tops of the apical portions, it is often necessary to do so. Refer to Tables 2 and 3 in Example 1 for some average root canal diameters as measured 2 mm from the apex of each root canal. In Table 2 and Table 3, the largest average diameter in the apical portion for a particular type of tooth measured in the sampling was 0.54 mm while the smallest average was 0J8 mm. Note that the tip diameter of operative middle portion instruments, as indicated hereinabove, typically range from .06 mm to .40 mm, more typically from about .08 mm to about .15 mm and most typically from about .08 mm to about .1 mm. In light of the apical portion diameters that are likely to be encountered, as indicated in Table 2 and Table 3, and the tip diameters of the instruments used to clean the operative middle portion just above the apical portion, it is apparent that widening is often necessary inorder to enable irrigation needles to adequately deliver inigants. It is not necessary for the entire apical portion to be widened up to about .35 mm or about .40 mm; just enough of the apical portion should be widened so that the irrigants can be delivered as needed. However, the length of files used to widen the apical portion is preferably sufficient to at least approximately reach the apex. Accordingly, the top of the abrading portion may be flared to enable the upper area of the apical portion to be widened up to about .40 mm while the tip diameter which is at or near the apex is preferably significantly smaller. Note that in addition to abrading at least the top of the apical portion, it may also be necessary to widen the diameter at the region of the base of the operative middle portion with the widening at the top of the apical portion. Note that before widening the apical portion of the root canal, it is preferable to make a predetermination of the desired diameter. This predetermination is preferably made in light of average diameters, wall thicknesses, etc. for the particular root canal being cleaned. As indicated hereinabove, Table 2 and Table 3, hereinbelow in Example 1 , provide a sampling of such moφhometric data. An example of an optional set of instruments designed for improving the access into the apical root portion is shown in Figure 21. The set comprises four file instruments 270a, 270b, 270c and 270d. Each file instrument comprises a handle 272 connected to a file 274. Each file 274 has a top end 276 where the file joins handle 272. When utilized to widen the access into the apical root portion of a root canal, file 270a is first introduced followed sequentially by file 270b, 270c and then 270d. Each file terminates at a tip 278 located opposite top end 276. A file instrument such as file instrument 270a or a set of file instruments such as 270a, 270b, 270c and 270d comprises a second endodontic instrument means for optionally, improving access into the apical root portion after the pulp material has been essentially removed from the operative middle portion by the first endodontic instrument means. Each file 274 of the file instruments designed for improving access to the apical root portion of a root canal is configured to have an abrading portion 279 along at least a portion of the length of file 274. The entire length of each file 274 can be configured with an abrading portion 279, however, abrading portion 279 preferably extends from tip 278 part way upward towards top end 276 such that the remainder of file 274 is relatively smooth. More particularly, each file is preferably configured with an abrading portion along less than about half of the length of the file and more preferably about one- third of the length between tip 278 and top end 276. Accordingly, the abrading portion may have any suitable length such as 3 mm or 10 mm; however, the abrading portion in a prefened configuration is about 5 mm or about 6 mm. The abrading portions as well as the tips can have a similar or identical configuration to the abrading portions and tips of the files disclosed herein for cleaning either the operative middle portion of the root canal or the apical root portion. However, the abrading portions and tips are preferably rounded as shown in Figure 21. As indicated above, the length of a file such as files 274a, 274b and 274c is preferably sufficient such that when the file is inserted into the root canal the tip can at least approximately reach the apex and the abrading portion 279 of the file can improve the access into the apical portion of the root canal. Although files used to improve the access into the apical root portion may be long enough to approximately reach the apex, the files can be used to improve the access as long as the files can reach the bottom of the operative middle portion and the top of the apical root portion. Such file lengths are typically within a range from about 8 mm to about 35 mm, more typically in a range from about 14 mm to about 35 mm and most typically in a range from about 12 mm to about 33 mm. The length of the abrading portion is generally within a range from about 1 mm to about 35 mm, more preferably in a range from about 2 mm to about 16 mm and most preferably in a range from about 3 mm to about 6 mm. The abrading portion is preferably long enough so that the entire apical portion can be abraded as well as at least the bottom of the operative middle portion. Note that stops such as stop 140 may alternatively be utilized with instruments used to improve the access into the apical root portion. In an optional set of instruments used to improve the access into an apical root portion, the file tips of the instruments preferably all have about the same diameter as shown in Figure 21 at 278a-d. The diameter of the tips is generally within a range from about .06 mm to about 1 mm, however, the tips preferably have a diameter of about .08 mm. In a less prefened embodiment, the tip diameter of each file may also increase sequentially. As shown in Figure 21 , the diameter of the abrading portions 279a-d increases from the tips 278a-d towards the top of the abrading portions. The diameter of the abrading portion at the top is preferably within a range from about .1 mm to about .4 mm and is more preferably in a range from about .2 mm to about .35 mm. As shown in Figure 21, each successive file has an abrading portion, 279a, 279b, and 279c which is successively larger in diameter at the top of the abrading portion than the abrading portion of the preceding file. Accordingly, a set may have files with abrading portions having the following respective top diameters: about .2 mm, about .25 mm, about .3 mm and about .35 mm. Each abrading portion in such a set has a different taper as is shown in Figure 21. Figure 21, however, also shows that the taper of the smooth or shank portions above the abrading portions may have essentially the same taper so that the taper of the shank portions remains essentially constant as the different files in the set are sequentially inserted. However, the shanks portions may have any suitable configuration. Accordingly, the diameter at top end 273, in addition to being greater than the diameter of the abrading portion, can also be equal to or less than the diameter of abrading portion 279 or tip 278. As mentioned above, the apical portion may be alternatively cleaned by abrading the apical portion. Typically, the instruments used to optionally improve the access into the apical portion, the apical portion access instruments, have the same lengths as the instruments optionally used thereafter to abrade the apical portion so that the entire apical portion is first widened and then cleaned in an abrasive manner. The instruments, however, have very different tip diameters and tapers along their respective abrading portions. The apical portion access instruments generally have much smaller tip diameters and much greater tapers than the instruments used to abrasively clean the apical portion for safe widening of apical portions. Refer to Example 2 and the accompanying Figures 36C-D for a discussion of specific instruments utilized and to observe the alteration of the apical portion after the apical portion widening phase and the apical portion cleaning phase. Before the apical root portion is abrasively cleaned, it is preferable to obtain further x-ray images while an instrument is inserted into a root canal to determine the desired working length of the instrument. In establishing the working length, the state of the apex and the periapical tissues should also be considered. The states most frequently shown in radiography are shown in Figure 34A-C wherein the apical portion of root canals 354a-c of roots 352a-c are depicted. Figure 34A depicts a root canal 354a of a vital tooth without periapical rarefaction as shown by the normal border with the bone at 356a. Figure 34B depicts an infected root canal 354b without periapical rarefaction as shown by radiolucency 358b. Figure 34C depicts an infected root canal 354c with apical and periapical resoφtion as shown by radiolucency 358c. If the practitioner identifies the condition of the root canal as being that depicted in Figures 34A or Figure 34B, then the working length of an instrument used to abrasively clean the apical root portion is in a range from about 0 to about 2 mm less than the distance from the occlusal surface to the radiographic apex of the tooth. However, if the root canal condition is infected and has apical and periapical resoφtion as depicted in Figures 34C, then the apical root portion may be abrasively cleaned up to about 1.5 mm or about 0.5 mm from the radiographic apex or more particularly about 1 mm. An example of an optional set of instruments designed for removing and abrasively cleaning essentially all remaining pulp material from the apical portion of a root canal is shown in Figure 22. The optional set comprises three file instruments 280a, 280b and 280c. Each file instrument comprises a handle 282 connected to a file 284. Each file 284 has a top end 283 where the file joins handle 282. When utilized to clean the apical root portion of a root canal, file 280a is first introduced into the apical root portion followed by file 280b and then 280c. Each file terminates at a tip 288 located opposite top end 283. A file instrument such as file instrument 280a or a set of file instruments such as 280a, 280b, and 280c are refened to herein as apical portion cleaning instruments and are examples of means for cleaning the apical root portion by abrading the apical root portion. More specifically, such instruments and sets of instruments as disclosed herein are examples of third endodontic instrument means for optionally, abrasively cleaning and removing essentially all remaining pulp material from the apical root portion after the pulp material has been essentially removed from the operative middle portion. Note that the means for cleaning the apical root portion, after the pulp material has been essentially removed from the operative middle portion, by deliverying an irrigant into the apical portion and also the third endodontic instrument means are both examples of means for cleaning the apical root portion after the pulp material has been essentially removed from the operative middle portion. Tips 288a-c can have any configuration, however, tips 288a-c preferably have minimal cutting capability to decrease the likelihood of ledging. An example of a suitable configuration for tips 288a-c that is designed to minimize the cutting ability of the tips is that of the round tip shown in Figure 17B. Each file 284 of the file instruments designed for abrasively cleaning the apical root portion of a root canal is configured to have an abrading portion 289 along at least a portion of the length of file 284. The entire length of each file 284 can be configured with an abrading portion 289, however, abrading portion 289 preferably extends from tip 288 part way upward towards top end 283 such that the remainder of file 284 is relatively smooth. More particularly, each file is preferably configured with an abrading portion along less than about half of the length of the file and more preferably about one-third of the length between tip 288 and top end 283. The abrading portion 289 can have a similar or identical configuration to the abrading portion of the file or files used to clean the operative middle portion of the root canal or the files used to improve the access into the apical root portion. The length of an optional apical portion abrading file such as files 284a, 284b and 284c is sufficient such that when the files are inserted into the root canal the tips can at least approximately reach the apex and the abrading portion 289 of the files can substantially contact and abrasively clean the pulp material in the apical portion of the root canal. Such file lengths are generally within a range from about 8 mm to about 35 mm, more typically in a range from about 14 mm to about 35 mm and most typically in a range from about 12 mm to about 33 mm. The length of the abrading portion is generally within a range from about 1 mm to about 35 mm, more preferably in a range from about 2 mm to about 16 mm and most preferably in a range from about 3 mm to about 6 mm. Note that stops such as stop 140 may alternatively be utilized with instruments used to abrasively clean the apical root portion. The diameter of the abrading portion is generally within a range from about .06 mm to about 1.4 mm. As shown in Figure 22, each successive file has an abrading portion, identifed as 289a-c, which is successively larger in diameter at the top of the abrading portion than the abrading portion of the preceding file. The diameter of the tips 288a-c of each optional apical portion abrading file may be increased incrementally such that each sequentially utilized abrasive cleaning instrument has a slightly larger tip diameter than the preceding instrument as shown in Figure 22 and Figure 23 or the tips diameters may be about equal in diameter like the tips shown in Figure 21. Additionally, the taper of files 284 from tip 288 to the top end of the abrading portion may be constant as shown in Figure 22. The taper may also increase from file to file like the files shown in Figure 21 or like instruments shown in Figure 35 in optional set 470. The diameter at top end 283 is shown being greater than the diameter of the abrading portion. However, the diameter at the top end of the file can also be equal to or less than the diameter of abrading portion 289 or tip 288. The abrading portion 289 of each file 284 of file instruments 280 is formed by twisting a blank so as to form a spiral. Files having such spiral-type abrading portions are prefened. The abrading portion 289 preferably has few spirals such that the action of abrading portion 289 against the walls or surfaces of the apical portion of the root canal is relatively gentle. Such an abrading portion is less aggressive as fewer spirals results in tines that have a wider angle. Figure 23 depicts an alternative embodiment of files configured for optionally, abrasively cleaning the apical portion of a root canal. The set of optional instruments depicted in Figure 23 comprises three file instruments 290a, 290b and 290c. Each file instrument comprises a handle 292 connected to a file 294. Each file 294 has a shank portion 296 above an abrading portion 298. Shank portion 296a has substantially the same diameter along its length and the diameter of shank portion 296a is approximately the same as the diameter of shank portion 296b and 296c. The diameter of abrading portion 298a is essentially constant along the length of abrading portion 298a. Similarly, abrading portions 298b and 298c also have substantially constant diameters. The diameter of abrading portion 298b is larger than the diameter of abrading portion 298a and the diameter of abrading portion 298c is larger than the diameter of abrading portion 298b. Figure 24 depicts an additional alternative embodiment of files configured for optionally, abrasively cleaning the apical portion of a root canal. The set of instruments depicted in Figure 24 comprises three optional file instruments 300a, 300b and 300c. Each file instrument comprise a handle 302 connected to a file 304. Each file 304 has a shank portion 306 above an abrading portion 308. Shank portion 306a has substantially the same diameter along its length and the diameter of shank portion 306a is approximately the same as the diameter of shank portions 306b and 306c. Each abrading portion 308 extends from each respective shank portion 306 with a shape that is generally elliptical. Additionally, the width of each successive abrading portion 308 is larger than that of the preceding abrading portion. More specifically, the width of each successive abrading portion is larger at its midpoint than at the midpoint of the preceding abrading portion. Figure 25 depicts file 284a inserted into apical portion 264 of root canal 252a. The apical root portion file instruments are generally moved in a different pattern compared to the operative middle portion file instruments due primarily to the different perimeter anatomies of the two portions. A root canal generally becomes more cylindrical towards the apical portion such that a root canal that has a perimeter anatomy that is essentially elliptical in shape within the operative middle portion tapers to an essentially cylindrically shaped perimeter anatomy within the apical portion. An elliptical perimeter anatomy typically requires that the practitioner move the file around the perimeter and/or flex the rotating file against the surfaces or walls in a milling motion such that the tip is moved to many locations around the perimeter. Due to the more cylindrical anatomy of an apical root portion, it becomes much less necessary, and virtually impossible to flex a rotating file in a milling motion. It is generally adequate to merely rotate the file within the apical root portion and/or move the file in a longitudinal motion. More specifically, after the file reaches the apex or approximately reaches the apex, the file is preferably moved upward while simultaneously being rotated, and it is withdrawn in order to be cleaned before being reintroduced. Since file 284a is generally not moved around the perimeter as in cleaning the operative middle portion, the center of motion, such as the center of rotation, of file 284a generally conesponds with the center of the root canal. In contrast, the center of motion when the operative middle portion is cleaned is at various locations as the file is moved around the root canal. The files used to optionally clean the apical root portion in an abrasive manner can be designed for primarily longitudinal movement, rotational movement or combinations thereof. Since it is generally not necessary to flex a file when abrasively cleaning the apical root portion as the apical root portion is typically rounder than other sections of a root canal, apical root portion files need not necessarily have the same properties as the operative middle portion files in terms of flexibility, rigidity and resilience. The files used to abrasively clean the apical portion are, however, preferably sufficiently flexible to adjust to the anatomy or structure of a root canal in a manner that enables the tip of the file to reach the apex. The files also preferably have sufficient rigidity to apply pressure against the walls or surfaces of the root canal as the abrading portion of the file is urged against the walls of the root canal and simultaneously moved in an abrasive cleaning motion even after the file has moved throughout the length of the root canal. Additionally, an optional file configured for abrasive use in an apical root portion preferably has adequate resilience to avoid being substantially deformed as the file passes through a root canal and also as the abrading portion is applied against the walls of the root canal. Figure 26A depicts a longitudinal cross-sectional view of tooth 240 after both root canals 252a and 252b have been cleaned. Figure 26B depicts a cross-sectional view of tooth 240 taken along cutting line 26B— 26B in Figure 26A. From the view shown in Figure 26B, it is clear that essentially all pulp material 250 has been removed from root canal 252a. Figure 26C is a transverse cross-sectional view of root canal 252a taken along cutting line 26C--26C in Figure 26A through cementum 248 and dentin 244 to depict the configuration of the cleaned and shaped root canal. The view shown in Figure 26C shows in phantom lines the original configuration of the perimeter of the pulp canal 252a and the configuration of the cleaned and shaped walls 268a. While the root canal is cleaned, it is also generally simultaneously shaped for subsequent filling with a filling material such as gutta percha. Cleaning and shaping a root canal, such as pulp canal 252a, to yield a cleaned and shaped root canal, such as shaped walls 268a, generally necessitates the widening of portions of the pulp canal and smoothing some contours of the pulp canal to yield a wider and smoother canal. The amount of dentin removed during the cleaning and shaping is preferably no more than just sufficient to adequately shape the root canal for subsequent filling. Because the perimeter of the root canal is followed during cleaning and shaping of the root canal, particularly the coronal portion and the operative middle portion, the original anatomy of the root canal or shape of the perimeter is substantially maintained. Accordingly, when the original perimeter is, for example, generally elliptical such as the cross-sectional shape of pulp canal 252a, the resulting cleaned and shaped root canal has a perimeter that is still generally elliptical such as shaped walls 268a as shown in Figure 26C. Similarly, if the original shape of the perimeter of a root canal as seen from a transverse cross-sectional view, such as the anatomies or perimeter configurations shown in Figures 7, 8 and 9B, is generally circular, laminar or tear shaped, then the cleaned and shaped walls will also be generally circular or tear shaped. In other words, the original anatomy of the root-canal controls the shape of the resulting cleaned and shaped anatomy due to the cleaning techniques enabled by the present invention. In contrast, prior art methods yield a final anatomy that is dictated by the shape of the instrument. As shown in Figures 15 A-F, prior art methods result in an anatomy with a significant footprint from the instrument without even cleaning all of the perimeter of the root canal. In addition to failing to fully clean the root canal, the tooth can be overly thinned, perforations may result or the tooth may be unnecessarily weakened when cleaned by such prior art methods. Figures 27A-27J are transverse cross-sections of exemplary files that can be utilized to clean the operative middle portion, to optionally improve the access to the apical root portion or to optionally clean the apical root portion of the root canal in an abrasive manner. Each file has a different abrading portion. All of the files in combination with their respective abrading portions disclosed herein are examples of means for removing and cleaning of pulp material as the file instrument is operatively moved. Additionally, each abrading portion disclosed herein is an example of a means for abrading a root canal. Conventional file designs can also be utilized within the scope of the present invention. Accordingly, the files are not limited to the designs shown in Figures 27A-27J. The files preferably, however, are configured in a manner such that when the potential for breakage is minimized. For example, a file with a square cross-section may be prefened over a triangular cross-section as the file with a square cross-section has a greater mass and is accordingly less likely to break. Additionally, a file configured with tines or extensions having wide angles are generally prefened over those with narrow angles. However, the prefened tine configuration depends primarily on the particular use as in some instances it is desirable to aggressively cut while in others the root canal can be passively cut. When it is more desirable to aggressively cut, it may be prefened for example to utilize a file with relatively narrow tines. Figure 27 J depicts a file 310 with a generally square-shaped transverse cross- section and truncated corners 312. Abrasive grit or abrasive material 314 is located on truncated corners 312. Similarly such abrasive grit can be located around a file having any cross-sectional shape and be an effective abrading portion. The abrasive grit may be any of the abrasive materials discussed above such as diamonds. The transverse cross-section of a file shown at Figure 27A corresponds to a file as shown in Figure 17A. In Figure 28, a file instrument 320 is shown cleaning operative middle portion 160 of a root canal. Instrument 320 has a handle 322 connected to file 324 formed by machining a groove into a metal blank. Note that handle 322 is adapted for manual use, however, a handle such as handle 202 designed for mechanical rotation may also be used. Figure 29 depicts another embodiment of a file instrument shown at 330. File instrument 330 has a handle 332 which is particularly adapted for use with a mechanical instrument. The file instruments of the present invention can, however, be utilized with any suitable handle configuration. All of the handles disclosed herein are examples of end means for grasping and operatively moving a file in an abrasive action. File instrument 330 further comprises a file 334 which is preferably used to clean the operative middle portion. File 334 has an abrading portion comprising protrusions or barbs 335 at the upper end of the file and a combination of barbs 335 and knurled surface 337 at the lower end. Figures 30-33 are depictions of various tips of files within the scope of the present invention. EXAMPLES OF THE PREFERRED EMBODIMENTS Testing was conducted to identify some of the anatomical characteristics of different teeth. The results of this testing are reported in Example 1. Additionally, Example 2-4 are hypothetical examples presented solely to illustrate some embodiments of the present invention. Note that reference is made in Example 2 to Figure 35 and Figures 36A-D. The hypothetical examples are not to be construed as limiting the spirit and scope of the invention as these hypothetical examples were produced in furtherance of reducing the present invention to practice. Example 1 Table 2 and Table 3 presented hereinbelow provide data regarding the anatomical characteristics of root canals of different teeth. More particularly, average measurements are provided of the canal diameters and the wall thicknesses of root canals at a location 2 mm from the apex of each root canal. A practioner should bear these average measurements in mind when optionally widening the apical portion or cleaning the apical portion. Note that the roots of the first molars are referenced by their position with the abreviations m,v, d, and 1 for the terms mesial, vestibular, distal and lingual. Table 2/Root Canal Anatomical Characteristics Table 3/Root Canal Anatomical Characteristics Example 2 This example describes, in relation to Figure 35 and Figures 36A-36D, an exemplary system and method for cleaning a root canal after the root canal has been properly accessed. After a tooth has been identified as requiring root canal therapy, an x-ray image is obtained in order to determine the state of health of a tooth as well as the structure and anatomical characteristics of the tooth. After all carious tissue has been removed and any old fillings have been infiltrated, a dam is installed. Before the instruments designed for use in the operative middle portion or the apical portion of the root canal are utilized, the pulp chamber must be properly opened so that adequate access can be gained to the anatomical root canal. Access is gained by removing the top of the pulp chamber, preferably with an appropriate diamond bur instrument. The contents in the pulp chamber are then removed with the aid of appropriate inigants. Examples of appropriate i igants include hydrogen peroxide, primarily for use in the canals of living teeth, or sodium hypochlorite, primarily for the canals in necrotic teeth. If desired a cuspidectomy may be performed. It is then preferable to remove or reduce dentinal or enamel protrusions or inegularities such as dentinal shelves, that may obscure or hinder access of instruments into the operative root canal by rectification of such protrusions with an appropriate instrument which preferably utilizes diamonds for abrasion. Figure 36A depicts a tooth 740 before the removal of dentinal shelf 266 above root canal 252a. Dotted line 550 in Figure 36A depicts the desired realignment through rectification in order to provide greater access for instrumentation during the subsequent phases. Rectified root canal 252a depicted in Figures 36B-D after subsequent phases shows that rectification would enable an instrument to be inserted in a relatively straight manner though the operative coronal portion 260 and the operative middle portion 262. Although, an instrument would need to flex within the apical portion 264 of root canal 252a due to its curvature, the required flexing is minimized as a result of the removal of dentinal shelf 266 above root canal 252a. Since the apical portion of root canal 252b is essentially straight, rectification of dentinal shelf 266 above root canal 252b would also enable an instrument to be inserted up to apex 254b through the apical portion 264 in an essentially straight configuration. The progressive phases depicted in Figures 36A-D are similar to the phases shown in Figures 19A, 19F, 25 and 26. For example, Figure 36A depicts the same phase as is shown in Figure 19A. Figures 36A-D, however, better depict the changes of the shape of pulp canal 252a after each phase. The same numbers are used for the elements of tooth 740 as are used for tooth 240. Note that pulp material 250 is not shown in Figures 36A-D so that the changes to pulp canal 252a are clearly visible after each phase. As discussed hereinbelow, Figure 36B-D respectively depict root canal 252a of tooth 740 after cleaning operative coronal portion 262, after widening apical portion 264 and after cleaning apical portion 264. After any necessary rectification, the working length is determined for the files used to clean the operative middle portion. The appropriate working length is determined by radiographically identifying the length of the operative root canal and then subtracting 3 mm from the length identified from the x-ray image. It is necessary to subtract 3 mm from the overall x-ray length in order to compensate for any distortions in the x-ray image and to avoid interfering with the apical portion while the operative middle portion is being prepared. After identifying the length of the root canal of a tooth and determining the working length of the files to be used, instruments can then be selected which have a length such that essentially all pulp material can be anatomically cleaned from the operative middle portion of a root canal without significantly removing pulp material from the apical root portion. Figure 35 depicts three sets of instruments identified at 410, 440 and 470 which are used to prepare a root canal. The sets of instruments identified respectively at 410, 440 and 470 are respectively used to clean the operative middle portion, to improve access into the apical portion and to clean the apical root portion. Operative Middle Portion Phase and Related Sets of Instruments Tables 4A, 4B and 4C presented hereinbelow describe the dimensions of three different set of instruments which can be used to clean the operative middle portion in different teeth depending on the particular operative root canal length. These three sets are preferably sold as part of a kit. Although, the kit includes several sets of instruments, only one set of instruments is typically used for cleaning the operative middle portion. The practitioner selects from several sets in the kit depending on the particular length of the operative coronal portion and the operative middle portion. The instruments in Tables 4A, 4B and 4C have lengths which are respectively 16 mm, 17 mm and 20 mm. In this example, the set of operative middle portion instruments selected for use in a tooth is the set presented in Table 4C due to the combined length of the operative coronal portion and the operative middle portion of the operative root canal. The set of instruments for cleaning the operative middle portion detailed in Table 4C conesponds with the set of instruments shown in Figure 35 at 410. Since only one set of instruments is used to clean the operative middle portion only one set is shown in Figure 35 at 410. Table 4 A/Operative Middle Portion Instruments (16 mm) Table 4B/Operative Middle Portion Instruments (17 mm) Table 4C/Operative Middle Portion Instruments (20 mm) As shown in Tables 4A, 4B and 4C, the operative middle portion instruments in the sets may have exactly the same tip diameters or may have tip diameters which are essentially the same. More particularly, the instruments in the set detailed in Table 4B both have a tip diameter of J 0 mm while the instruments in the sets presented in Table 4 A and Table 4C have a tip diameter of either .10 mm or J 3 mm. In each set, the second instrument has a greater taper than the file of the first instrument. As indicated above, set 410 conesponds with the set presented in Table 4C. As shown, instruments 410a and 410b have files 414a and 414b. Each file has a shank portion 416 which tapers to an abrading portion 419 configured like conventional K-files and terminating at a tip 418. Smooth shank portion 416 may be used to accommodate stops to adjust the working length of file 414. Note that the file of each instrument detailed in Tables 4A, 4B and 4C has a 2 mm smooth portion or shank portion above the abrading portion. Handles 412a and 412b are respectively positioned on smooth shank portions 416a and 416b. These handles are configured for attachment to a handpiece. The sets of instruments presented in Table 4A and 4B have a similar appearance to set 410, however, the files of the instruments in Table 4B have an abrading portion configured to conespond with Hedstrom-type files. The operative middle portion instruments in each set are formed from stainless steel. The instruments all have sufficient rigidity to apply pressure against root canal surfaces as each instrument is flexed or curved against root canal surfaces and simultaneously moved in a cleaning motion. Each instrument also has adequate resilience to avoid being substantially deformed as the instrument is flexed or curved to urge the abrading portion against root canal surfaces and as the instrument is simultaneously moved in a cleaning motion. Accordingly, a practitioner can move the instrument around the perimeter of the operative middle portion of the root canal using the contours of the operative middle portion as a guide for the movement of the instrument such that the original anatomy is enlarged and not significantly altered. After set 410, as detailed in Table 4C, is selected, the pulp chamber is flooded with an inigation fluid or filled with a chelating lubricant gel, if the canal is atresic. The instruments in set 410 are then attached to a handpiece to move the instruments in either a rotating or reciprocating motion. These instruments can also be manually moved. Instrument 410a and then 410b are then sequentially urged against the root canal for about one minute in conformance with the anatomy of the root canal. More particularly, the instruments are applied to the perimeter of the canal, acting on any protuberances or jagged edges in order to rectify the first two portions, the operative middle portion and the operative coronal portion, while still conforming to the anatomy of the canal. After cleaning the operative middle portion, the root canal may appear as does root canal 252a of tooth 740 shown in Figure 36B. Figure 36B shows that dentinal shelf 266 has been fully rectified. The other contours of root canal 252a have been followed to clean operative middle portion 262. As a result, the diameter of the root canal in operative middle portion 262 has been widened, although, the original perimetrical anatomy has not been substantially altered, particuarly in the bottom half of the operative middle portion 262 of root canal 252a. A third instrument may also be added to each set of instruments which is an aggresive abrasion instrument having the same dimensions as the second instrument in each set. Each aggresive abrasion instrument may have an abrading portion equally divided between an upper section covered with abrasive particles such as diamonds and a lower section that is twisted like the abrading portions of the other instruments in the sets. So for example, a third instrument in set 410 having a file with an upper section configured for aggresive abrasion has an abrading portion that is 18 mm long below a shank portion that is 2 mm long. The upper half of the shank portion is not twisted and is covered with diamonds while the lower half is twisted and has a length of about 9 mm. If the instruments are configured with a handle that enables them to be used with a handpiece configured for adjusting the working length of the instrument then the lengths of the file, the abrading portion and the shank portion are longer. More particularly, instead of lengths of 16 mm, 14 mm and 2 mm for the total file length, abrading portion length and shank portion length of the instruments described in Table 4 A, the respective lengths are 19 mm, 16 mm and 3 mm. Similarly, the lengths of the instruments listed in Table 4B as being 17 mm, 15 mm, 2 mm for the total file length, abrading portion length and shank portion length of the instruments are respectively 23 mm, 20 mm and 3 mm when attached to a handle that enables the instrument to be used in a manner such that it can be moved within the chuck of the handpiece. Finally, the lengths of the instruments listed in Table 4C as being 20 mm, 18 mm, 2 mm for the total file length, abrading portion length and shank portion length of the instruments are respectively 27 mm, 24 mm and 3 mm when attached to a handle that enables the instrument to be used in a manner such that it can be moved within the chuck of the handpiece. Apical Portion Widening Phase and Related Sets of Instruments A probe is then inserted to the apex of the root canal and another x-ray image is obtained. After the length has been determined the accessibility of the apical portion is assessed. If the apical portion is initially to small to permit entry of an irrigation cannula then an optional set of instruments is selected for use in improving the access into the apical root portion or stated otherwise to enlarge the constricted region between the operative middle portion and the apical portion. This is achieved by manually moving one or more instruments until the transition zone between the operative middle portion and the apical root portion has been appropriately instrumented to have a diameter of about .40 mm, which is suitable for accommodating the diameters of the smallest inigation needles. Again the practitioner has a comprehensive kit with several sets of instruments which are designed for improving access into the apical root portion after the pulp material has been removed from the operative middle portion of a root canal. Each set is designed for use in a tooth with a different operative root canal length. Accordingly, only one set from the kit is selected for use in operative root canal based on the length of the particular anatomical root canal being treated. Tables 5A, 5B and 5C detail the dimensions of instruments with file lengths which are respectively 21 mm, 25 mm and 30 mm. In this example, the set presented in Table 5B is selected. The set presented in Table 5B is shown in Figure 35 as set 440. Table 5 A/Apical Widening Instruments (21 mm) Table 5B/ApicaI Widening Instruments (25mm) The files of the instruments in the sets detailed in Tables 5A, 5B and 5C are formed from stainless steel. Each file has three sections including a smooth shank portion, a square portion and an abrading portion. As indicated above, the set presented in Table 5B conesponds with set 440 shown in Figure 35. Note, however, with the exception of length, the instruments detailed in Table 5 A and Table 5C would appear just like set 440. Instrument 440a has a file 444a with smooth shank portion 446a, a square portion 447a, an abrading portion 449a and a file tip 448a. As shown, the smooth shank portion 446a is the top section of file 444a and a handle 442 is positioned on shank portion 446a. Smooth shank portion 446a tapers to square portion 447a which is between shank portion 446a and abrading portion 449a. The smooth shank portion enables stops be positioned on the file to adjust the working length of the file. Each smooth shank portion of each file has a length of about 5 mm with various diameters. The instruments can be used for all operative lengths that are likely to be encountered in clinical practice through the positioning of the stops at the predetermined lengths. While the instruments can be offered in a more expanded series of millimetrically different lengths, the use of stops is acceptable, particularly since, these instruments are manually moved. In each set, the diameter at the top of the square portion of instrument number 1 and instrument number 2 is respectively .30 mm and .40 mm. The abrading portion is formed by twisting the square section so that the abrading portion has a K-file configuration. The instruments in each set all have the same tip diameters. The taper of the files from the tip (D,) to the diameter at the top of the square portion (D 3 ) remains constant and is respectively .04 and .06 for instrument number 1 and instrument number 2 in each set. Preferably, instrument 1 is first utilized and then instrument 2 to obtain, in a gradual manner, the desired enlargement of the specific transition zone between the operative middle portion and the apical portion. This enlargement is also preferably achieved without significantly changing the diameter of the apical portion of the canal. Accordingly, the tip diameter (D,) of the various instruments in this set remains constant while the diameter at the top of the cutting area or abrading portion (D 2 ), located 5 mm from the tip, is graduated from one instrument to the next, reaching a maximum diameter of .38 mm. The rest of the shaft, up to the handle, does not have a cutting surface. To the extent that these instruments are used to expand the apical portion of the canal, the practitioner should constantly bear in mind the average diameters of the canals and the average thicknesses of the parietal walls at the apex, as listed in Table 2 and Table 3. After widening the apical portion of the root canal with the set shown at 440 in Figure 35 and as detailed in Table 5B, the root canal may appear as does root canal 252a in Figure 36C with a widened apical portion 264. More particuarly, the region of root canal 252a extending from the bottom of operative middle portion 262 to the top half of apical portion 264 has been noticeably widened. The bottom half of apical portion 264 has also been widened but to a much lesser degree. Apical Portion Cleaning Phase and Related Sets of Instruments After the access into the apical portion has been adequately widened as discussed hereinabove and as shown in Figure 36C, the apical portion is cleaned. Cleaning is halted at the working length as determined by the operator which should be at the apex. The practitioner should determine this length beforehand, based on the biological condition of the apico-periapical region, in terms of the morphometrics of the diameters and thicknesses at the apex as set forth in the Table 2 and Table 3, and in accordance with the amount of widening to be applied to the apical portion of the canal. In this example, Example 2, a set of instruments is decribed for cleaning the apical portion in an abrasive manner after the portion of the root canal above the apical portion has been cleaned. In Example 4, the preferred method of cleaning of the apical portion through irrigation is used in combination with the instruments described above in this example for cleaning the portions above the apical portion. Again sets of instruments are provided with each set having a different length. Three sets of instruments are described hereinbelow which are designed for removing and cleaning essentially all pulp material from the apical root portion after access into the apical root portion has been improved by a set of instruments such as set 440 detailed in Table 5B. In some instances, the instruments described in this example can also be used to clean the pulp material from the root canal immediately after the operative middle portion has been cleaned by a set of instruments such as the sets presented in Table 4C. Tables 6 A, 6B and 6C detail the dimensions of instruments with file lengths which are respectively 21 mm, 25 mm and 30 mm. However, please note that only instruments from Table 6B are used in the tooth being cleaned in this example. The set of instruments detailed in Table 6B are shown in Figure 35 as set 470. Set 470 includes instruments 470a-l which respectively conespond with instruments 1-12 in the set presented in Table 6B. The instruments in set 470 have a similar appearance as the instruments in set 440. Instruments 470a-l have a handle 472 opposite a file 474. Each file 474 has a smooth shank portion 476a, a square portion 477, an abrading portion 479 and a file tip 478. The sets of instruments presented in Table 6A and 6C have a similar appearance to instruments detailed in Table 6B and shown at 470, however, the files have different lengths. The taper of the files from the tip (D,) to the diameter at the top of the square portion (D 3 ) is provided in each table. Table 6A/ApicaI Cleaning Instruments (25 mm) Table 6B/Apical Cleaning Instruments (25 mm) Table 6C/Apical Cleaning Instruments (30 mm) After the apical portion has been properly widened, the practitioner selects a set of files having the appropriate length, such as one of the sets presented in Tables 6 A, 6B or 6C. To ensure that the files have an appropriate working length, it may be necessary to place stops around the shank portions of the files identified for example at 416a, 446a and 476a. The practitioner then selects an instrument from the set identifed as having an appropriate length for introduction into the root canal down to the apical portion. As indicated above, in this example, an instrument is selected from the set detailed in Table 6B, which is shown in Figure 35 as set 470. After selecting an instrument, the practitioner then determines, based on feel and experience, whether the file is appropriately sized or whether a larger or smaller file is needed. For instance, if the practitioner selects instrument number 2 from the set detailed in Table 6B and shown in Figure 35 at 470b which has a tip diameter of J 5 mm and the file binds after insertion, then the practitioner would switch to instrument number 1 which has a tip diameter of JO mm. Similarly, if instrument number 2 is too loose then the practitioner would then switch to instrument number 3 which has a tip diameter of .20 mm. The practitioner then uses that appropriately sized instrument to clean the apical portion of the root canal by hand. If the practitioner concludes after using an appropriately sized file, that further instrumentation is still needed within the apical portion then the instrument with the next largest file may be used. It is typically unnecessary to use a third instrument with an even larger file after using a series of two instruments. However, the practitioner may clean the apical root portion with a series of more than two instruments as deemed necessary by the practitioner in order to fully clean the apical portion. After the apical portion of the root canal has been cleaned with the set shown at 470 in Figure 35 and as detailed in Table 6B, the root canal may appear as does root canal 252a shown in Figure 36D with a cleaned apical portion 264. More particuarly, after use of an instrument such as instrument 2 from Table 6B shown at 470b, apical portion 264 may appear as shown. Note that cleaning apical portion 264 has substantially widened the bottom half of apical portion 264 while the top half is less significantly flared when compared to its appearance before being cleaned. The appearance of apical portion 264 results from the different configurations of the respective abrading portions of instruments used to widen and to clean the apical portion. More particularly, the diameter of the tip (D,) and the diameter at the top of the abrading portion (D 2 ) of the last instrument used to widen the apical portion, instrument 440b, are respectively .08 mm and .38 mm while instrument 470b has a tip diameter (D,) of .15 mm and the diameter at the top of the abrading portion (D 2 ) is .25 mm. Stated otherwise, the .06 taper of abrading portion 449b results in much greater flaring than the .02 taper of abrading portion 479b while the large tip diameter of instrument 440b causes the widening of the lower half of apical portion 264. Set 410 and set 440 are preferably disposed after use. However, since only one or two instruments from set 470 are used, it is preferable to replace or clean the instruments used from set 470. All of the sets of instruments described in this example may be sold together as a comprehensive kit or various sets may be grouped together as kits intended for use with teeth of particular lengths. For example, the sets used in the tooth cleaned in this example which are detailed in Table 4C, 5B and 6B may be sold together. Additionally, since set 410 and set 440 are intended to be single use sets these sets may also be sold together as a single use disposable kit. Example 3 This example describes another exemplary system for cleaning a root canal after the root canal has been properly accessed. Operative Middle Portion Instruments The sets of instruments designed for use in the operative middle portion of a root canal are set in Tables 7 A, 7B and 7C. In contrast to the sets of operative middle portion instruments described in Example 2, each of these sets include four instruments instead of only two instruments. The lengths of the files in these sets include the various lengths that are likely to be encountered in clinical practice which range predominantely but not exclusively from 15 mm to 20 mm. Longer lengths, 25 mm, are typically needed for the middle segment of canine teeth. Accordingly, the files in each set of instruments have the following respective lengths: 17 mm, 20 mm and 25 mm. The lengths of the instruments in these three sets encompass the average variations in length that are likely to be encountered in clinical practice and in terms of the overall length of the operative coronal portion and the operative middle portion of various operative canals. However, please note that other sets may also be useful as these three sets are merely illustrative. For example, it may be useful to have a greater series of sets with lengths ranging from 15 mm to 20 mm in 1 mm increments and an additional set having a length of 25 mm. As in Example 2, one set of instruments is selected based on the length of the tooth. Accordingly, after the length of the operative middle portion has been determined then either the set of instruments detailed in Table 7A, 7B or 7C is selected and if necessary stops may be utilized to adjust the working length of the file. When the length of the operative middle portion has been appropriately determined, each of these sets of instruments can be used to anatomically clean essentially all pulp material from the operative middle portion of a root canal without significantly removing pulp material from the apical root portion. Table 7 A/Operative Middle Portion Instruments (17 mm) Table 7B/Operative Middle Portion Instruments (21 mm) The instruments in the sets detailed in Table 7A and Table 7B include a first instrument with a tip diameter of about .10 mm while the other instruments have a tip diameter of about .13 mm. The first and second instruments in the set presented in Table 7C have tip diameters of about .10 mm while the third and fourth instruments have tip diameters of about .13 mm. It is often useful to begin instrumenting with a slightly smaller tip diameter, however, the difference in diameter is so small that these tip diameters are considered to be essentially the same size. The difference is particularly insignificant when compared with the incremental increase in the size of the diameter tip from instrument to instrument of conventional instruments used in conventional cleaning techniques. The sets of instruments described in this example would be expected to require more time to use than the instruments described in Example 2 as there are more instruments in each set. However, all of the sets can be used to clean the operative middle portion without substantially changing the original anatomy of the root canal. More particularly, each instrument is configured to enable a practitioner to move the file along a side of the operative middle portion in a manner such that the original anatomy is enlarged without being modified to have just the shape of the instrument. Note that the abrading portion of each file extends along the entire length of each file. Accordingly, each file is capable of simultaneously abrading both the operative coronal portion and the operative middle portion. In any event, the abrading portion extends beyond the conventional 16 mm length of instruments in present use. Since sets are provided in different lengths it is not necessary to use stops to adjust the length of the file as the handle of the instrument ensures that the instrument stops safely at the proper working depth. Thus, the use of sets of instruments with graduated lengths eliminates the problems associated with traditional stopping depths. More particularly, the sets reduce the amount of time required to position the instruments at the desired length and eliminate the risk of bacterial contamination of the instruments due to handling. Apical Portion Widening Instruments The access into the apical portion is improved, if necessary, after the operative middle portion has been cleaned. More particularly, it is necessary to widen the access into the apical root portion of the root canal in order to enable inigants to be delivered as needed. The dimensions of a set of instruments which can be used for this purpose are set forth in Table 5. The files of each instrument have a length of about 35 mm and an abrading portion which is about 5 mm long. Table 8/Apical Widening Instruments (35 mm) The instruments would each be expected to be useful for improving access into the apical root portion after the pulp material has been removed from the operative middle portion of a root canal. However, such a set of instruments would be expected to require more time to use than one of the sets of instruments described in Example 2 as there are more instruments in this set. Apical Portion Cleaning Instruments After the access into the apical portion has been adequately widened, the apical portion is cleaned. One of the sets of instruments detailed in Tables 6 A, 6B or 6C may be used to clean the apical portion or alternatively the set detailed in Table 9 may be used. Each instrument in the set described in Table 9 has a file with a working length of about 35 mm and an abrading portion which is about 5 mm long. The files of the instruments all have the same tip diameters and have increasing larger tapers. Table 9 The set of instruments detailed in Table 9 have longer files than the sets provided in Tables 6A, 6B and 6C so more stops would be necessary. In most other respects the set in Table 9 is very similar to the other sets discussed in Example 2 for cleaning the apical portion. Note, however, that the set in Table 9 begins with smaller tip diameters which may be useful in some instances. Example 4 This example describes an exemplary system for cleaning a root canal without abrasively cleaning the apical portion. The apical portion is cleaned after the operative middle portion has been cleaned with set 410 as set forth in Example 2. Access into the apical portion may also have been improved through the use of set 440 as described in Example 2. Cleaning of the apical portion is then initiated by inserting a cleaning instrument into the apical portion as shown in Figure 20A and Figure 20B and deliverying irrigants. The cleaning instrument is a cannula 760 of an endodontic irrigator tip 720, as previously described in reference to Figure 20 A and Figure 20B. After syringe 790 has been used to deliver irrigants into root canal 782, the inigants and any remaining debris may be removed by any suitable method such as aspiration using irrigator tip 720 coupled to an aspirator device so that the tooth appears as shown in Figure 20B at 780. Note in addition to set 410 and set 440 being disposable after use, irrigator tip 720 is also preferably disposable. Note also that instead of a large set of instruments like set 470, only a single irrigator tip need be used so it is much less expensive to merely irrigate. It is also less time intensive since it is not necessary to use a series of apical instruments. All of the instruments described in this example may be sold individually or together as a comprehensive kit. The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrated and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope. What is claimed is:

Claims: 1. An endodontic instrument system adapted for anatomical cleaning of the operative coronal portion, the operative middle portion and the apical root portion of an operative root canal in a tooth, the endodontic instrument system comprising: first endodontic instrument configured for use in the operative middle portion of an operative root canal to anatomically clean essentially all pulp material from the operative middle portion, the first endodontic instrument including a file having a top end opposite a tip, the file having a length conesponding to at least the combined length of the operative coronal portion and the operative middle portion in order to remove pulp material from essentially all of the operative middle portion of the operative root canal, the file having an abrading portion for removing pulp material, the file being able to flex such that the abrading portion is urged against root canal surfaces while the file is rotated and moved in a cleaning motion, thereby enabling contours of the operative middle portion to be used as a guide for movement of the file in conformance to the anatomical shape of the operative middle portion while effecting removal and cleaning of pulp material from essentially all of the operative middle portion, and a handle connected to the top end of the file, the handle being configured to enable a user to operatively move the file in an abrasive action while bending and flexing the file within the operative middle portion of the operative root canal; and an apical portion cleaning instrument adapted for cleaning the apical root portion through the delivery of an irrigant after the pulp material has been essentially removed from the operative coronal portion and the operative middle portion by the first endodontic instrument. 2. An endodontic instrument system as defined in claim 1 , wherein the file of the first endodontic instrument has sufficient rigidity to apply pressure against the root canal surfaces via the abrading portion as the file is flexed to urge the abrading portion against root canal surfaces and as the file is simultaneously moved in a cleaning motion. 3. An endodontic instrument system as defined in claim 1 , wherein the file of the first endodontic instrument is configured to enable a practitioner to move the file around the perimeter of the operative middle portion of the operative root canal. 4. An endodontic instrument system as defined in claim 1. wherein the file of the first endodontic instrument is configured to enable a practitioner to move the file along a side of the operative middle portion in a manner such that the tip does not remain primarily in one position as the operative middle portion is cleaned. 5. An endodontic instrument system as defined in claim 1 , further comprising a stop configured to be positioned on the file of the first endodontic instrument in order to limit insertion of the file into the operative coronal portion and the operative middle portion without substantially extending into the apical portion. 6. An endodontic instrument system as defined in claim 1 , wherein the file of the first endodontic instrument has a shank portion above the abrading portion and below the handle, wherein the shank portion is adapted to receive a stop. 7. An endodontic instrument system as defined in claim 1 , wherein the file of the first endodontic instrument has a length that limits the penetration of the file in the root canal to essentially only the operative middle portion of the root canal. 8. An endodontic instrument system as defined in claim 1 , further comprising a second endodontic instrument configured to adequately improve access into the apical root portion after the pulp material has been essentially removed from the operative middle portion by the first endodontic instrument such that irrigants can be delivered into the apical portion of the root canal from an inigation needle. 9. An endodontic instrument system as defined in claim 1 , further comprising a second endodontic instrument configured for improving access into the apical root portion after the pulp material has been essentially removed from the operative middle portion by the first endodontic instrument, wherein the second endodontic instrument includes: a file having a top end opposite a tip, the file having a length that enables the file to reach within the apical portion of the root canal, the file having an abrading means for removing pulp material, the abrading means being located on a portion of the file such the abrading means can be moved against the root canal to improve the access into the apical portion of the root canal; and a handle connected to the top end of the file of the second endodontic instrument. 10. An endodontic instrument system as defined in claim 1 , wherein the apical portion cleaning instrument is an irrigator tip adapted for coupling with a delivery device to deliver an inigant into the apical portion after the pulp material has been essentially removed from the operative middle portion. 11. An endodontic instrument system as defined in claim 1 , wherein the apical portion cleaning instrument is an inigator tip coupled to a delivery device to deliver an irrigant into the apical portion after the pulp material has been essentially removed from the operative middle portion. wherein the inigation tip is coupled to a delivery device. 12. An endodontic instrument system adapted for anatomical cleaning of the operative coronal portion, the operative middle portion and the apical root portion of an operative root canal in a tooth, the endodontic instrument system comprising: a set of first endodontic instruments configured for sequential use in the operative middle portion of an operative root canal to anatomically clean essentially all pulp material from the operative middle portion, each instrument in the set comprising a file having a tip opposite a top end, the file having a length conesponding to at least the combined length of the operative coronal portion and the operative middle portion in order to remove pulp material from essentially all of the operative middle portion of the operative root canal, the file having an abrading portion for removing pulp material, the abrading portion being located on the file and extending from the tip along at least most of the file toward the top end, the file being able to flex such that the abrading portion is urged against root canal surfaces while the file is rotated and moved in a cleaning motion, thereby enabling contours of the operative middle portion to be used as a guide for movement of the file in conformance to the anatomical shape of the operative middle portion while effecting removal and cleaning of pulp material from essentially all of the operative middle portion, and a handle connected to the top end of the file, the handle being configured to enable a user to operatively move the file in an abrasive action while bending and flexing the file within the operative middle portion of the root canal; and an apical portion cleaning instrument adapted for cleaning the apical root portion through the delivery of an inigant after the pulp material has been essentially removed from the operative coronal portion and the operative middle portion by the first endodontic instrument. 13. An endodontic instrument system as defined in claim 12, wherein the file of each instrument in the set of first endodontic instruments has sufficient rigidity to apply pressure against the root canal surfaces via the abrading portion as each file is flexed to urge the abrading portion against root canal surfaces and as each file is simultaneously moved in a cleaning motion. 14. An endodontic instrument system as defined in claim 12, wherein the file of each instrument in the set of first endodontic instruments is configured to enable a practitioner to move the file around the perimeter of the operative middle portion of the operative root canal. 15. An endodontic instrument system as defined in claim 12, wherein the file of each instrument in the set of first endodontic instruments is configured to enable a practitioner to move the file along a side of the operative middle portion in a manner such that the tip does not remain primarily in one position as the operative middle portion is cleaned. 16. An endodontic instrument system as defined in claim 12, wherein the files of all of the instruments in the set of first endodontic instruments have essentially the same tip diameter while having distinct top end diameters to enable the files to be sequentially introduced into the operative middle portion such that each successive file has a greater top end diameter than that of the preceding file. 17. An endodontic instrument system as defined in claim 12, wherein the files of all of the instruments in the set of first endodontic instruments have distinct tapers to enable the files to be sequentially introduced into the operative middle portion such that each successive file has a greater taper than that of the preceding file. 18. An endodontic instrument system as defined in claim 12, wherein at least one of the instruments in the set of first endodontic instruments is an aggresively abrasive instrument with a file having an abrading portion with abrasive particles on at least an upper section of the file that enable aggresive abrasion. 19. An endodontic instrument system as defined in claim 12, wherein the file of each instrument in the set of first endodontic instruments has essentially the same length. 20. An endodontic instrument system as defined in claim 12, wherein the file of each instrument in the set of first endodontic instruments has a length that limits the penetration of the file in the root canal to essentially only the operative middle portion of the root canal. 21. An endodontic instrument system as defined in claim 12, further comprising at least one stop configured to be positioned on each file in order to limit insertion of each file into the operative coronal portion and the operative middle portion without substantially extending into the apical portion. 22. An endodontic instrument system as defined in claim 12, wherein the file of each instrument in the set of first endodontic instruments has a shank portion above the abrading portion and below the handle, wherein the shank portion is adapted to receive a stop. 23. An endodontic instrument system as defined in claim 12, further comprising a second endodontic instrument configured to adequately improve access into the apical root portion after the pulp material has been essentially removed from the operative middle portion by the first endodontic instrument such that irrigants can be delivered into the apical portion of the root canal from an inigation needle. 24. An endodontic instrument system as defined in claim 12, further comprising a second endodontic instrument configured for improving access into the apical root portion after the pulp material has been essentially removed from the operative middle portion by the first endodontic instrument, wherein the second endodontic instrument includes: a file having a top end opposite a tip, the file having a length that enables the file to reach within the apical portion of the root canal, the file having an abrading portion for removing pulp material, the abrading portion being located on a portion of the file such the abrading portion can be moved against the root canal to improve the access into the apical portion of the root canal; and a handle connected to the top end of the file of the second endodontic instrument. 25. An endodontic instrument system as defined in claim 12, wherein the apical portion cleaning instrument is an inigator tip adapted for coupling with a delivery device to deliver an irrigant into the apical portion after the pulp material has been essentially removed from the operative middle portion. 26. An endodontic instrument system as defined in claim 12, wherein the apical portion cleaning instrument is an irrigator tip coupled to a delivery device to deliver an irrigant into the apical portion after the pulp material has been essentially removed from the operative middle portion.wherein the irrigation tip is coupled to a delivery device. 27. An endodontic instrument system adapted for anatomical cleaning of the operative coronal portion, the operative middle portion and the apical root portion of an operative root canal in a tooth, the endodontic instrument system comprising: a set of first endodontic instruments configured for sequential use in the operative middle portion of an operative root canal to anatomically clean essentially all pulp material from the operative middle portion without significantly extending into the apical root portion, each instrument in the set comprising a file having a tip opposite a top end, the file having a length conesponding to at least the combined length of the operative middle portion and the operative coronal portion, the file having an abrading portion located on the file and extending from the tip along at least most of the file toward the top end, the file being able to flex such that the abrading portion is urged against root canal surfaces while the file is rotated and moved in a cleaning motion, thereby enabling contours of the operative middle portion to be used as a guide for movement of the file in conformance to the anatomical shape of the operative middle portion while effecting removal and cleaning of pulp material from essentially all of the operative middle portion, and a handle connected to the top end of the file, the handle being configured to enable a user to operatively move the file in an abrasive action while flexing the file within the operative middle portion of the root canal, and wherein the files of all of the instruments in the set of first endodontic instruments have essentially the same length and tip diameter while having distinct top end diameters to enable files to be sequentially introduced into the operative middle portion such that each successive file has a greater top end diameter than that of the preceding file; and an irrigator tip adapted for coupling with a delivery device to deliver an irrigant into the apical portion after the pulp material has been essentially removed from the operative middle portion. 28. An endodontic instrument system adapted for anatomical cleaning of the operative coronal portion, the operative middle portion and the apical root portion of an operative root canal in a tooth, the endodontic instrument system comprising: a first endodontic instrument configured for use in the operative middle portion of an operative root canal to anatomically clean essentially all pulp material from the operative middle portion, the first endodontic instrument including a file having a top end opposite a tip, said file having a length conesponding to at least the combined length of the operative coronal portion and the operative middle portion in order to remove pulp material from essentially all of the operative middle portion of the operative root canal, the file having an abrading portion for removing pulp material, the file being able to flex such that the abrading portion is urged against root canal surfaces while the file is rotated and moved in a cleaning motion, thereby enabling contours of the operative middle portion to be used as a guide for movement of the file in conformance to the anatomical shape of the operative middle portion while effecting removal and cleaning of pulp material from essentially all of the operative middle portion, and a handle connected to the top end of the file, the handle being configured to enable a user to operatively move the file in an abrasive action while bending and flexing the file within the operative middle portion of the operative root canal; a second endodontic instrument configured for improving access into the apical root portion after the pulp material has been essentially removed from the operative middle portion by the first endodontic instrument; and an apical portion cleaning instrument adapted for cleaning the apical root portion after the pulp material has been essentially removed from the operative coronal portion and the operative middle portion. 29. An endodontic instrument system as defined in claim 28, wherein the file of the first endodontic instrument has sufficient rigidity to apply pressure against the root canal surfaces via the abrading portion as the file is flexed to urge the abrading portion against root canal surfaces and as the file is simultaneously moved in a cleaning motion. 30. An endodontic instrument system as defined in claim 28, wherein the file of the first endodontic instrument is configured to enable a practitioner to move the file around the perimeter of the operative middle portion of the operative root canal. 31. An endodontic instrument system as defined in claim 28, wherein the file of the first endodontic instrument is configured to enable a practitioner to move the file along a side of the operative middle portion in a manner such that the tip does not remain primarily in one position as the operative middle portion is cleaned. 32. An endodontic instrument system as defined in claim 28, further comprising a stop configured to be positioned on the file of the first endodontic instrument in order to limit insertion of the file into the operative coronal portion and the operative middle portion without substantially extending into the apical portion. 33. An endodontic instrument system as defined in claim 28, wherein the file of the first endodontic instrument has a shank portion above the abrading portion and below the handle, wherein the shank portion is adapted to receive a stop. 34. An endodontic instrument system as defined in claim 28, wherein the file of the first endodontic instrument has a length that limits the penetration of the file in the root canal to essentially only the operative middle portion of the root canal. 35. An endodontic instrument system as defined in claim 28, wherein the second endodontic instrument comprises a file having a top end opposite a tip, the file having a length that enables the file to reach within the apical portion of the root canal, the file having an abrading portion for removing pulp material, the abrading portion being located on the file such the abrading portion can be moved against the root canal to improve the access into the apical portion of the root canal, and a handle connected to the top end of the file of the second endodontic instrument. 36. An endodontic instrument system as defined in claim 28, wherein the second endodontic instrument is configured to adequately improve access into the apical root portion after the pulp material has been essentially removed from the operative middle portion such that irrigants can be delivered into the apical portion of the operative root canal from an inigation needle. 37. An endodontic instrument system as defined in claim 28. wherein the apical portion cleaning instrument comprises an irrigator tip adapted for coupling with a delivery device to deliver an irrigant into the apical root portion after the pulp material has been essentially removed from the operative middle portion. 38. An endodontic instrument system as defined in claim 28, wherein the apical portion cleaning instrument comprises an inigator tip and wherein the irrigation tip is coupled to a delivery device to deliver an irrigant into the apical root portion after the pulp material has been essentially removed from the operative middle portion . 39. An endodontic instrument system as defined in claim 28, wherein the apical portion cleaning instrument comprises a file with a top end extending from a handle, wherein the file has a tip opposite the top end. wherein the file has an abrading portion for removing pulp material, the abrading portion being located on the file such that the abrading portion can remove the pulp material from the apical portion of the root canal. 40. An endodontic instrument system adapted for anatomical cleaning of the operative coronal portion, the operative middle portion and the apical root portion of an operative root canal in a tooth, the endodontic instrument system comprising: a set of first endodontic instruments configured for sequential use in the operative middle portion of an operative root canal to anatomically clean essentially all pulp material from the operative middle portion, each instrument in the set including a file having a tip opposite a top end, said file having a length corresponding to at least the combined length of the operative coronal portion and the operative middle portion in order to remove pulp material from essentially all of the operative middle portion of the operative root canal, the file having an abrading portion for removing pulp material, the abrading portion being located on the file and extending from the tip along at least most of the file toward the top end, the file being able to flex such that the abrading portion is urged against root canal surfaces while the file is rotated and moved in a cleaning motion, thereby enabling contours of the operative middle portion to be used as a guide for movement of the file in conformance to the anatomical shape of the operative middle portion while effecting removal and cleaning of pulp material from essentially all of the operative middle portion, and a handle connected to the top end of the file, the handle being configured to enable a user to operatively move the file in an abrasive action while bending and flexing the file within the operative middle portion of the operative root canal; a second endodontic instrument configured for improving access into the apical root portion after the pulp material has been essentially removed from the operative middle portion by the first endodontic instrument; and an apical portion cleaning instrument adapted for cleaning the apical root portion after the pulp material has been essentially removed from the operative coronal portion and the operative middle portion. 41. An endodontic instrument system as defined in claim 40, wherein the file of each instrument in the set of first endodontic instruments has sufficient rigidity to apply pressure against the root canal surfaces via the abrading portion as each file is flexed to urge the abrading portion against root canal surfaces and as each file is simultaneously moved in a cleaning motion. 42. An endodontic instrument system as defined in claim 40, wherein the file of each instrument in the set of first endodontic instruments is configured to enable a practitioner to move the file around the perimeter of the operative middle portion of the operative root canal. 43. An endodontic instrument system as defined in claim 40, wherein the file of each instrument in the set of first endodontic instruments is configured to enable a practitioner to move the file along a side of the operative middle portion in a manner such that the tip does not remain primarily in one position as the operative middle portion is cleaned. 44. An endodontic instrument system as defined in claim 40, wherein the files of all of the instruments in the set of first endodontic instruments have essentially the same tip diameter while having distinct top end diameters to enable the files to be sequentially introduced into the operative middle portion such that each successive file has a greater top end diameter than that of the preceding file. 45. An endodontic instrument system as defined in claim 40, wherein the files of all of the instruments in the set of first endodontic instruments have distinct tapers to enable the files to be sequentially introduced into the operative middle portion such that each successive file has a greater taper than that of the preceding file. 46. An endodontic instrument system as defined in claim 40, wherein the file of each instrument in the set of first endodontic instruments has essentially the same length. 47. An endodontic instrument system as defined in claim 40, wherein the file of each instrument in the set of first endodontic instruments has a length that limits the penetration of the file in the root canal to essentially only the operative middle portion of the root canal. 48. An endodontic instrument system as defined in claim 40, further comprising at least one stop configured to be positioned on each file in order to limit insertion of each file into the operative coronal portion and the operative middle portion without substantially extending into the apical portion. 49. An endodontic instrument system as defined in claim 40, wherein the file of each instrument in the set of first endodontic instruments has a shank portion above the abrading portion and below the handle, wherein the shank portion is adapted to receive a stop. 50. An endodontic instrument system as defined in claim 40, wherein at least one of the instruments in the set of first endodontic instruments is an aggresively abrasive instrument with a file having an abrading portion with abrasive particles on at least an upper section of the file that enable aggresive abrasion. 51. An endodontic instrument system as defined in claim 40, wherein the second endodontic instrument comprises: a file having a top end opposite a tip, the file having a length that enables the file to reach within the apical portion of the operative root canal, the file having an abrading portion for removing pulp material, the abrading portion being located on a portion of the file such the abrading portion can be moved against the root canal to improve the access into the apical portion of the operative root canal; and a handle connected to the top end of the file of the second endodontic instrument. 52. An endodontic instrument system as defined in claim 40, wherein the second endodontic instrument is configured to adequately improve access into the apical root portion after the pulp material has been essentially removed from the operative middle portion such that irrigants can be delivered into the apical portion of the operative root canal from an irrigation needle. 53. An endodontic instrument system as defined in claim 40. wherein the apical portion cleaning instrument comprises an irrigator tip adapted for coupling with a delivery device to deliver an irrigant into the apical root portion after the pulp material has been essentially removed from the operative middle portion. 54. An endodontic instrument system as defined in claim 40, wherein the apical portion cleaning instrument comprises an inigator tip and wherein the inigation tip is coupled to a delivery device to deliver an irrigant into the apical root portion after the pulp material has been essentially removed from the operative middle portion . 55. An endodontic instrument system as defined in claim 40, wherein the apical portion cleaning instrument comprises a file with a top end extending from a handle, wherein the file has a tip opposite the top end, wherein the file has an abrading portion for removing pulp material, the abrading portion being located on the file such that the abrading portion can remove the pulp material from the apical portion of the root canal. 56. An endodontic instrument system adapted for anatomical cleaning of the operative coronal portion, the operative middle portion and the apical root portion of an operative root canal in a tooth, the endodontic instrument system comprising: a set of first endodontic instruments configured for sequential use in the operative middle portion of an operative root canal to anatomically clean essentially all pulp material from the operative middle portion without significantly extending into the apical root portion, each instrument in the set including a file having a tip opposite a top end, said file having a length corresponding to at least the combined length of the operative coronal portion and the operative middle portion in order to remove pulp material from essentially all of the operative middle portion of the operative root canal, the file having an abrading portion for removing pulp material, the abrading portion being located on the file and extending from the tip along at least most of the file toward the top end, the file being able to flex such that the abrading portion is urged against root canal surfaces while the file is rotated and moved in a cleaning motion, thereby enabling contours of the operative middle portion to be used as a guide for movement of the file in conformance to the anatomical shape of the operative middle portion while effecting removal and cleaning of pulp material from essentially all of the operative middle portion, wherein the files of all of the instruments in the set of first endodontic instruments have essentially the same length and tip diameter while having distinct top end diameters to enable files to be sequentially introduced into the operative middle portion such that each successive file has a greater top end diameter than that of the preceding file, and a handle connected to the top end of the file, the handle being configured to enable a user to operatively move the file in an abrasive action while bending and flexing the file within the operative middle portion of the operative root canal; a second endodontic instrument configured for improving access into the apical root portion after the pulp material has been essentially removed from the operative middle portion by the first endodontic instrument; and an apical portion cleaning instrument adapted for cleaning the apical root portion after the pulp material has been essentially removed from the operative coronal portion and the operative middle portion. 57. An endodontic instrument system adapted for mechanical rotation to anatomically cleaning the operative coronal portion and the operative middle portion of an operative root canal in a tooth, the endodontic instrument system comprising: at least two endodontic instruments configured for sequential use in the operative coronal portion and the operative middle portion of an operative root canal to anatomically clean essentially all pulp material from the operative middle portion without significantly extending into the apical root portion of the root canal, each instrument comprising a file having a tip opposite a top end, said file having a length conesponding to at least the combined length of the operative coronal portion and the operative middle portion, said file having an abrading portion for removing pulp material, said file being able to flex such that the abrading portion is urged against root canal surfaces while the file is rotated and moved in a cleaning motion, thereby enabling contours of the operative middle portion to be used as a guide for movement of the file in conformance to the anatomical shape of the operative middle portion while effecting removal and cleaning of pulp material from essentially all of the operative middle portion, and a handle connected to the top end of the file, the handle being configured to enable a user to operatively move the file in an abrasive action while bending and flexing the file within the operative middle portion of the root canal; and wherein one of the endodontic instruments is an aggresively abrasive instrument with a file having an abrading portion with abrasive particles on at least an upper section of the file that enable aggresive abrasion. 58. An endodontic instrument system as defined in claim 57, wherein the file of the aggresive abrasion instrument includes a lower section below the upper section that is less abrasive than the upper section. 59. An endodontic instrument system as defined in claim 57, wherein the file of the aggresive abrasion instrument includes a lower section below the upper section that is less abrasive than the upper section so that the upper section may be urged against root canal surfaces for aggresive shaping while less aggresively abrading lower portions of the operative middle portion of the operative root canal. 60. An endodontic instrument adapted for mechanical rotation to anatomically clean the operative coronal portion and the operative middle portion of an operative root canal in a tooth, the endodontic instrument comprising: a file having a top end opposite a tip, said file having a length conesponding to at least the combined length of the operative coronal portion and the operative middle portion, said file having an abrading portion with abrasive particles on at least an upper section of the file for aggresive abrasion and with a lower section below the upper section that is less abrasive than the upper section, said file being able to flex such that the abrading portion is urged against root canal surfaces while the file is rotated and moved in a cleaning motion, thereby enabling contours of the operative middle portion to be used as a guide for movement of the file in conformance to the anatomical shape of the operative middle portion while effecting removal and cleaning of pulp material from essentially all of the operative middle portion, and a handle connected to the top end of the file, the handle being configured to enable a user to operatively move the file in an abrasive action while bending and flexing the file within the operative middle portion of the root canal. 61. An endodontic instrument as defined in claim 60, wherein said lower section of the file that is twisted to have a fluted configuration. 62. An endodontic instrument as defined in claim 60, wherein the upper section has a length that is no greater than about half of the length of the file. 63. An endodontic instrument as defined in claim 60, wherein the upper section has a length that is in a range from about 4 to about 10 mm in length. 64. An endodontic instrument as defined in claim 60, wherein the abrasive particles are diamond particles. 65. An endodontic instrument as defined in claim 60, wherein the abrasive particles are selected from the group consisting of refractories of silicon carbide and fused alumina, aluminum oxide, natural aluminum oxide, alumina ceramics, glass, silicon dioxide, silicon carbide, boron nitride, and other comparably hard materials. 66. An endodontic instrument as defined in claim 60, wherein the abrasive particles have an average particle size in a range from about 30 μm to about 350 μm. 67. An endodontic instrument as defined in claim 60, wherein the abrasive particles are positioned on the upper section of the file with a thickness in a range from about 100 μm to about 700 μm. 68. An endodontic instrument as defined in claim 60, wherein said file has a shank portion above the abrading portion.

Inventors: FISCHER DAN E, RIITANO FRANCESCO, FISCHER, DAN, E., RIITANO, FRANCESCO
Applicants: ULTRADENT PRODUCTS INC, ULTRADENT PRODUCTS, INC.
Application year: 2000
Main classification: A61C5
IPC codes: A61C5, A61C17