Abstract:
Instruments and associated methods for performing endodontic treatment and that demand less time and fatigue onto the dentists and patients, while presenting the following accomplishments: debride the root canals in three dimensions and performing the optimal treatment; shape the root canals to facilitate the irrigation; these instruments are resistant to breakage and pressure while operating at high speed and torque; the instruments are capable of bypassing most obstacles, broken files, hypercalcification, curved roots canals, shoulders, and residual resistant pastes; and they present an alternative to arduous and expensive surgeries like endodontic or implant surgeries. As a result, they prevent fractures and procedural errors in making false canals or perforations of the root canals.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to instruments for endodontic use, and more particularly to apparatuses and associated methods for performing root canal treatment. 
       BACKGROUND OF THE INVENTION 
       [0002]    In endodontics it is necessary to thoroughly debride a root canal (or pulp chamber) of a tooth, in order to reduce the chances of bacterial growth in the root canal, and to improve the healing potential of the remaining healthy tissue. As used herein, debridement includes for example, the removal of dead, damaged, or infected tissue of the dental pulp, as well as hypercalcification, residual resistant paste, various constrictions, broken instruments, and fragments or foreign material lodged in the root canal. 
         [0003]    This debridement would ideally terminate at the apical foramen. The apical foramen is the opening at the apex of the root of the tooth, through which the nerve and blood vessels that supply the dental pulp pass. The dental pulp resides in the root canal and is comprised of living circulatory, connective, and nerve tissues. 
         [0004]    As part of the endodontic therapy, and following the debridement of the root canal, the endodontic clinician shapes the root canal prior to inserting a filler material in place of the original dental pulp. 
         [0005]    To this end, hand (i.e., manual) files and rotary files (i.e., electrically operated) commonly called spiral instruments are used for the treatment of root canals. Typically, these spiral instruments have a generally triangular, square, or rectangular cross section, and comprise edges (or corners) that attack the dental wall and strike the dentine wall at an acute angle. Consequently, these conventional files have a tendency to wear out prematurely and to break. 
         [0006]    In addition, these conventional files may bind when resisted by obstacles and eventually break inside the root canal, as they do not have a sufficient thickness to resist torsion fatigue induced thereon. Moreover, such files do not generally perform a complete rubbing of the dental wall in order to achieve a hermetic obturation of the root canal, thus yielding to a risk of infection. 
         [0007]    In addition, the tip of these spiral instruments is usually a non-cutting tip based on the assumption that a cutting tip will facilitate the formation of false canals. 
         [0008]    Conventionally, withdrawing segments of fractured instruments that cause root obstructions, was done by means of ultrasonic files. An exemplary technique requires the use of conventional manual files from No. 8 to 15 having a taper of 2%, in order to open a cutting around the lodged segment of the fractured instrument. However, this withdrawal technique involves the risk of introducing additional breakage of the newly used instrument, as well as opening false canals. As a result, this conventional technique has not generally yielded optimal results. 
         [0009]    Furthermore, in order to overcome obstructions resulting from hypercalcification, certain conventional treatment methods propose the enlargement of the root canal using files from No. 8 to 15 having a 2% taper, or C+ files followed by the use of rotary files (electrically operated) from No. 10 to 25 with a 2%, 4%, or 6% taper. However, this method also does not provide optimal results and introduces the risk of breakage of the newly used file, as well as opening false canals. 
         [0010]    The weakness of the conventional endodontic files in fracture or in procedural errors, is due to their cyclic fatigue and torsional stress, and the difficulties of removing the broken files, as explained in the following publications:
   Bahcall J K, et al., “The causes, prevention, and clinical management of broken endodontic rotary files,” Dent Today. 2005 November; 24(11):74, 76, 78-80; quiz 80, Department of Surgical Sciences, Marquette University School of Dentistry, USA, the abstract of which is available online at http://www.ncbi.nlm.nih.gov/pubmed/16358801.   Peters O. A., “Rotary Instrumentation: An endodontic perspective,” American Association of Endodontists, Winter 2008, which is available online at https://www.aae.org/uploadedfiles/publications_and_research/endodontics_colleagues_for_excellence_newsletter/winter08ecfe.pdf. This publication makes it clear that not all root canals lend themselves to rotary preparation, due to varying degrees of the clinicians&#39; skills and case complexity, and to the fact that rotary files may fracture rather unexpectedly or create procedural errors.   
 
         [0013]    The following references clarify that the fracture of an endodontic file may cause the endodontic treatment to have a lower success rate, and that fragments of files may be removed using a retrieval system; however, this procedure can be technically demanding, and several fragments may be left in-situ:
   Metzger, Z. et al., “The Self-Adjusting File (SAF). Part 1: Respecting the Root Canal Anatomy—A New Concept of Endodontic Files and Its Implementation,” Journal of Endodontics 36 (4): 679-90 (2010).   De-Deus, G. et al., “The Self-Adjusting File Optimizes Debridement Quality in Oval-shaped Root Canals,” Journal of Endodontics 37 (5): 701-5 (2011).   Siqueira Jr., J. F., et al. “Ability of Chemomechanical Preparation with Either Rotary Instruments or Self-Adjusting File to Disinfect Oval-shaped Root Canals,” Journal of Endodontics 36 (11): 1860-5 (2010).   
 
         [0017]    Although cylindro conical instruments have been used by dentists only in root canal filing material (spreaders) with a smooth surface, they have not been used to probe, shape, debride, catheterize, penetrate or bypass obstacles in root canal treatments. Reference is made to Carrotte, P., “Endodontics: Part 5 Basic instruments and materials for root canal treatment,” British Dental Journal 197, 455-464 (2004), Published online: 23 Oct. 2004, at http://www.nature.com/bdj/journal/v197/n8/full/4811738a.html Root canal filling instruments. 
         [0018]    In addition to the risks involved with the use of conventional treatment methods, there is a potential for damaging the apex or causing a shear in the coronal part or in the apical part of the root canal. 
         [0019]    Yet another disadvantage of the conventional treatment methods is that the instruments generally cannot penetrate difficult hypercalcifications, blockages, and narrow canals, nor can they probe the ledges or pierce the most resistant residual paste in the root canal. 
         [0020]    In addition, they cannot bypass lodged segments of fractured instruments in the root canals, nor can they remove dental plugs. Moreover, they cannot penetrate blockages resulting from root canal treatment, nor can they penetrate the obliterated coronary infundibula due to the high fracture risk. 
         [0021]    Still another disadvantage of the conventional treatment methods is that the instruments generally may not be totally suitable for use under elevated torque or high speed, due to the high fracture risk. In addition, the spiral instruments generally exert force on the dental wall and are therefore subjected to a reactive force. In fact, rubbing the dental wall does not facilitate penetration in the desired direction of the dental apex. 
         [0022]    Wherefore, there still remains an unsatisfied need for new endodontic instruments and associated methods of use for performing better root canal treatment. These instruments should penetrate or bypass most, if not all blockages in the root canals, while achieving optimal root canal treatment with optimal root canal shape, in order to maximize irrigation and hermetic obturation of the root canals. 
       SUMMARY OF THE INVENTION 
       [0023]    The present invention satisfies this need, and presents several preferred designs for endodontic instruments and associated methods of use for performing root canal treatment. These instruments penetrate or bypass most, if not all blockages in the root canal, while achieving optimal root canal treatment with optimal root canal shape, in order to maximize irrigation and hermetic obturation of the root canal. 
         [0024]    In addition, the treatment of a root canal with the instruments and methods of the present invention, while avoiding damage to either the root canal or the apex, is ensured a very high rate of success. 
         [0025]    Although the teeth and grooves of the endodontic instruments of the present invention may become worn with use, they will not easily break because they do not attack the radical dentine at weak pointed angles. In addition, the use of sandblasting to form the endodontic instrument helps to avoid corrosion of instrument resulting from stocking, storage, or usage. 
         [0026]    The various instruments of the invention surpass the conventional stainless steel hand files and the NiTi rotary instruments, and present numerous advantages among which are the following: 
         [0027]    The instruments are very flexible so that they may follow difficult curved root canals without damaging the apex, making a false canal, or causing a shear in the coronal part and the apex of the root canal. 
         [0028]    They penetrate the difficult hypercalcifications, obstructions and narrow canals. 
         [0029]    They probe the ledges of the root canal. 
         [0030]    They pierce residual, resistant pastes. 
         [0031]    They bypass fractured files, lentulos, posts, and fractured silver cones. 
         [0032]    They do not create false canals, shears and dental plugs. 
         [0033]    They allow the removal of pre-existing dental plugs. 
         [0034]    They penetrate blockages caused by an inadequate use of other instruments. 
         [0035]    They penetrate the obliterated coronary infundibula with low risk of fracture or of damaging the apex. 
         [0036]    Furthermore, these instruments successfully perform and facilitate the complete endodontic procedure: 
         [0037]    They penetrate root canals that other endodontic instruments fail to penetrate. 
         [0038]    They resist increased torque and high speeds (ranging from approximately 1.5 N to 5 N and from approximately 300-600 rpm) due to their high resistance. 
         [0039]    Their success in treating and retreating root canals helps to avoid expensive and painful endodontic surgeries and eventually implants in case of failure of endodontic treatments. 
         [0040]    To this end, each instrument of the present invention comprises a handle that secures an elongated tapered shank. The shanks of the instruments include cylindro-conical files having a circular cross section, which penetrate the root canals using most, if not the entirety of their peripheral surfaces, thus providing a better ability to resist torsion fatigue, to preserve the initial circular dental canal anatomy, and to attain a hermetical obturation of the root canals. The shanks can assume a variety of designs based on a combination of characteristics, including but not limited to: a roughed surface, a cutting surface, a smooth area, a conical cutting tip, a non-cutting tip, a beveled tip, and a non-beveled tip. 
         [0041]    Based upon the various designs of their shanks, the endodontic instruments may generally be categorized, as follows:
       1 st  Category: Instruments for catheterization and for passing through root obstacles.   2 nd  Category: Instruments for fine and curved roots.   3 rd  Category: Instruments that may be used for enlarging and shaping root canals.       
 
         [0045]    The instruments in the 1 st  Class of the 1 st  Category can be either hand operated or electrically rotating. Each of these instruments includes a lateral surface that contains a number of superficial horizontally, vertically, or transversally striated grooves that define slightly cutting edges, and that are either separated by smooth areas or sandblasted areas. The instruments in this class include a generally circular cross-section, and a conical tip that may be cutting or non-cutting, beveled or non-beveled. These instruments include hand operated files for root canal treatment that are preferably made from stainless steel (with nos. ranging from 10 to 25) or NiTi (with nos. ranging from 20 to 25) and electrically rotating NiTi files (with nos. ranging from 10-to 25), all with a taper of approximately 0, 1, 2, 3, or 4% and a length ranging from approximately 12 mm-32 mm. 
         [0046]    The instruments in the 2 nd  Class of the 1 st  Category are hand operated instruments having a series of horizontally, vertically, or transversally striated deep grooves with cutting edges, that are separated by restricted smooth or sandblasted areas or even instruments that are completely sandblasted. The instruments in this class include a generally circular cross section, and a conical tip that may be cutting or non-cutting. The shanks of these instruments range from No. 6 to 20. The shanks may be made from stainless steel, and range from No. 6 to 20. The shanks may alternatively be made from NiTi, and range from No. 20 to 40. The shafts of all these instruments have a taper of approximately 0%, 1%, 2%, and 4%, and a length that ranges from approximately 12 mm to 32 mm. 
         [0047]    The instruments of the 2 nd  Category preferably include electrically operated rotating NiTi instruments, each having a tapered shank with a series of transversal, deep, striated grooves with cutting edges. In other embodiments can alternatively, the instruments include a series of horizontally or vertically striated, deep grooves with cutting edges, that are separated by either smooth or roughened (i.e., sandblasted) restricted areas. These instruments include electrically rotating files for root canal treatment with nos. 10 to 20, and having an approximate 2% taper and a length ranging from approximately 21 mm to 32 mm. 
         [0048]    The instruments of the 3 rd  Category preferably include electrically operated rotating instruments, each having a shank with a generally circular cross section and a conical cutting or non-cutting tip, with a series of saw teeth that are separated by restricted smooth areas. In other embodiments, the shank can include horizontally, vertically, or transversally striated grooves. These instruments include electrically rotating files for root canal treatment with nos. ranging from 20 to 40, and having an approximate 4% to 10% taper and a length ranging from approximately 21 mm to 32 mm. 
         [0049]    The endodontic procedure being administered determines the selection of the category, the instruments within each category, and the sequential use of the selected instruments. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0050]    The various features of the present invention and the manner of attaining them will be described in greater detail with reference to the following description, claims, and drawings, wherein reference numerals are reused, where appropriate, to indicate a correspondence between the referenced items, and wherein: 
           [0051]      FIG. 1  comprises  FIGS. 1A and 1B , and represents two schematic illustrations of an exemplary hand operated (or electrically rotating) instrument having a long, tapered shank which includes superficial horizontally striated grooves with slightly cutting edges that are separated by smooth areas ( FIG. 1A ), and which includes deep horizontally striated grooves with cutting edges that are separated by restricted smooth areas ( FIG. 1B ), according to preferred embodiments of the present invention; 
           [0052]      FIG. 2  comprises  FIGS. 2A and 2B , and represents two schematic illustrations of an exemplary hand operated (or electrically rotating) instrument having a long, tapered shank which includes superficial vertically striated grooves with slightly cutting edges that are separated by smooth areas ( FIG. 2A ), and which includes deep vertically striated grooves with cutting edges that are separated by restricted smooth areas ( FIG. 2B ), according to preferred embodiments of the present invention; 
           [0053]      FIG. 3  comprises  FIGS. 3A and 3B , and represents two schematic illustrations of an exemplary hand operated (or electrically rotating) instrument having a long, tapered shank which includes continuous, superficial transversally striated grooves with slightly cutting edges that are separated by smooth areas ( FIG. 3A ), and which includes deep transversally striated grooves with cutting edges that are separated by restricted smooth areas ( FIG. 3B ), according to preferred embodiments of the present invention; 
           [0054]      FIG. 4  is a schematic illustration of an exemplary hand operated (or electrically rotating) instrument having a long, tapered shank with a beveled tip, and discontinuous, superficial transversally striated grooves with slightly cutting edges, separated by smooth areas, according to a preferred embodiment of the present invention; 
           [0055]      FIG. 5  is a schematic illustration of an exemplary hand operated (or electrically rotating) instrument having a long, tapered shank with superficial transversally striated grooves with slightly cutting edges, separated by roughened areas (such as by sandblasting), according to a preferred embodiment of the present invention; 
           [0056]      FIG. 6  is a schematic illustration of an exemplary hand operated instrument having a long, tapered shank with deep transversally striated grooves with cutting edges, separated by restricted smooth areas, according to a preferred embodiment of the present invention; 
           [0057]      FIG. 7  is a schematic illustration of an exemplary electrically rotating instrument having a long, tapered shank with deep transversally striated grooves with cutting edges, separated by restricted smooth areas, according to a preferred embodiment of the present invention; 
           [0058]      FIG. 8  is a schematic illustration of an exemplary electrically rotating (or hand operated) instrument having a long, tapered shank with a series of saw teeth separated by restricted smooth areas, according to a preferred embodiment of the present invention; 
           [0059]      FIG. 9  comprises  FIGS. 9A and 9B , and represents two schematic illustrations of an exemplary hand operated ( FIG. 9B ) and electrically rotating ( FIG. 9A ) spiral instrument with an upper cylindro-conical part having a conical tip, wherein the cylindro-conically shaped area is roughened, for example, by transversally grooved striations with cutting edges separated by restricted smooth or sandblasted areas, according to preferred embodiments of the present invention; 
           [0060]      FIG. 10  comprises  FIGS. 10A and 10B , and represents two schematic illustrations of an exemplary hand operated ( FIG. 10B ) and electrically rotating ( FIG. 10A ) instrument having a conical tip and a long, generally tapered shank that defines a series of cylindro-conically shaped areas (or sections) separated by spirally shaped sections, wherein the cylindro-conically shaped areas (or sections) are roughened by, for example, transversally grooved striations with cutting edges separated by restricted smooth areas, according to preferred embodiments of the present invention; 
           [0061]      FIG. 11  comprises  FIGS. 11A and 11B , and represents two schematic illustrations of an exemplary hand operated ( FIG. 11B ) and electrically rotating instrument ( FIG. 11A ) having a long, generally tapered shank that defines a series of spirally shaped sections separated by cylindro-conically shaped areas (or sections) that are roughened by, for example, transversally grooved striations with cutting edges separated by restricted smooth areas, according to preferred embodiments of the present invention; 
           [0062]      FIG. 12  comprises  FIGS. 12A and 12B , and represents two schematic illustrations of an exemplary hand operated ( FIG. 12B ) and electrically rotating ( FIG. 12A ) instrument having a conical tip and a long, generally tapered sand blasted shank that defines a series of cylindro-conically shaped areas (or sections) separated by spirally shaped sections, wherein the cylindro-conically shaped areas (or sections) are roughened by, for example, transversally grooved striations with cutting edges separated by restricted sand blasted areas, according to preferred embodiments of the present invention; 
           [0063]      FIG. 13  comprises  FIGS. 13A, 13B, 13C, and 13D , and illustrates a cross-sectional view of an exemplary tooth, with the cross-hatching removed for clarity of illustration, showing the sequential steps of progressively treating a root canal without a resistive path, obstruction, or blockage, using the instrument and process of the present invention; 
           [0064]      FIG. 14  comprises  FIGS. 14A, 14B, 14C, 14D, 14E, and 14F , and illustrates a cross-sectional view of an exemplary tooth, with the cross-hatching removed for clarity of illustration, showing the sequential steps of progressively treating a root canal that is blocked by a fragment of a broken instrument, such as a file, by bypassing the lodged fragment using the instrument and process of the present invention; 
           [0065]      FIG. 15  comprises  FIGS. 15A, 15B, and 15C  and illustrates a cross-sectional view of an exemplary tooth, with the cross-hatching removed for clarity of illustration, showing the sequential steps of progressively treating a root canal that is blocked by hypercalcification, by piercing the hypercalcification using the instrument and process of the present invention; 
           [0066]      FIG. 16  comprises  FIGS. 16A, 16B, and 16C  and illustrates a cross-sectional view of an exemplary tooth, with the cross-hatching removed for clarity of illustration, showing the sequential steps of progressively treating a root canal that is partially blocked by a shoulder, by bypassing the shoulder using the instrument and process of the present invention; 
           [0067]      FIG. 17  comprises  FIGS. 17A, 17B, and 17C  and illustrates a cross-sectional view of an exemplary tooth, with the cross-hatching removed for clarity of illustration, showing the sequential steps of progressively treating a root canal that is blocked by a residual resistant paste, by piercing and removing the resistant paste using the instrument and process of the present invention; 
           [0068]      FIG. 18  is a flow chart that illustrates the endodontic treatment process that does not exhibit signs of a resistive path, obstruction, or blockage, by selectively using the instruments of  FIGS. 1B, 2B, 3B, and 6 through 8  according to the present invention; 
           [0069]      FIGS. 19A and 19B  represent a flow chart that illustrates the endodontic treatment method of bypassing root obstructions resulting from fractured instruments, by selectively using the instruments of  FIGS. 1A, 1B, 2A, 2B, 3A, 3B , and  4  through  8  according to the present invention; 
           [0070]      FIGS. 20A and 20B  represent a flow chart that illustrates the endodontic treatment method of penetrating root obstructions resulting from hypercalcification, by selectively using the instruments of  FIGS. 1A, 1B, 2A, 2B, 3A, 3B, and 5 through 8  according to the present invention; 
           [0071]      FIGS. 21A and 21B  represent a flow chart that illustrates the endodontic treatment method of bypassing root obstructions resulting from a shoulder obstruction, by selectively using the instruments of  FIGS. 1A, 1B, 2A, 2B, 3A, 3B , and  5  through  8  according to the present invention; 
           [0072]      FIGS. 22A and 22B  represent a flow chart that illustrates the endodontic treatment method of penetrating root obstructions resulting from a previous root canal treatment, by selectively using the instruments of  FIGS. 1A, 1B, 2A, 2B, 3A, 3B, and 4 through 8  according to the present invention; and 
           [0073]      FIGS. 23A, 23B, 23C, 24A, 24B, 24C, 25A, 25B, 25C, 25D, 26A, 26B, 27A, 27B, 27C, 28A, 28B, 28C, 28D, 29A, 29B ,  29 C,  30 A,  30 B,  31 A,  31 B,  32 A,  32 B,  32 C,  33 A,  33 B,  33 C,  33 D,  34 ,  35 ,  36 A,  36 B,  36 C,  37 A,  37 B,  38 A, and  38 B are X-ray views that illustrate various cases treated by the instruments and methods of the present invention. 
       
    
    
       [0074]    It should be understood that the sizes of the different components in the figures might not be in exact proportion, and are shown for visual clarity and for the purpose of explanation. 
       DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0075]    The instruments of the present invention can be used for probing, enlarging, penetrating, and bypassing difficult root canals obstructions, they may be hand operated or electrically operated, they may have a continued or a discontinued rotation, and they may have reciprocal rotation, a clockwise rotation, or an anti-clockwise rotation. 
         [0076]    As it will be explained later in more specific details, each of these instruments comprises a handle that secures an elongated tapered shank. The cross section of the shank is generally circular, so as to eliminate sharp edges (or corners) that might otherwise attack the dental wall and strike the dentine wall at an acute angle, thus ultimately extending the life of the instrument. 
         [0077]    The shank can assume a variety of designs, based on a combination of characteristics, including but not limited to: a roughed surface, a cutting surface, a smooth area, a conical cutting tip, a non-cutting tip, a beveled tip, and a non-beveled tip. 
         [0078]    Based upon the various designs of their shanks, the endodontic instruments may be categorized as follows:
       1 st  Category: Instruments for catheterization and for passing through root obstacles.   2 nd  Category: Instruments for fine and curved roots.   3 rd  Category: Instruments that may be used for enlarging and shaping root canals.       
 
         [0082]    Each of these categories will now be described in more detail. 
         [0083]    1st Category: Instruments for Catheterization and for Passing Through Root Obstacles, Shoulders, Resistant Paste, and Hypercalcifications 
         [0084]    This category comprises two classes of instruments: 
         [0085]    First (1 st ) Class: Instruments for Passing Through Root Obstacles, Shoulders, Resistant Paste, and Hypercalcifications 
         [0086]    This class includes hand operated and electrically rotating instruments having a number of superficial horizontally, vertically, or transversally striated grooves (also referred to as “shallow grooves”) that define slightly cutting edges, and that are either separated by smooth areas or sandblasted areas or even instruments that are completely sandblasted. As used herein, the term “shallow” denotes a general depth that ranges between approximately 0.06 mm and 0.4 mm. The instruments in this class include a generally circular cross-section, and a conical tip that may be cutting or non-cutting, beveled or non-beveled. 
         [0087]    The shanks of the hand operated instruments may be made from stainless steel, and range from No. 10 to 25. The shanks of the hand operated instruments that are made from NiTi, preferably range from No. 20 to 25. The shafts of the electrically rotating NiTi instruments preferably range from No. 10 to 25. The shafts of all these instruments have a taper ranging from approximately 0% to 4%, and a length that ranges from approximately 12 mm to 32 mm. ( FIGS. 1-5 ). 
         [0088]    The more preferred embodiments of the instruments in this class that provide optimal results are the hand operated instruments Nos. 10, 15, and 20, with a shank taper with an approximate 2% taper, and that are made from stainless steel. Other preferred embodiments include the hand operated instruments No. 20 with an approximate 4% shank taper that is made from NiTi. Additional preferred embodiments include the electrically rotating instruments that are made from NiTi, Nos. 10, 15, and 20, with a shank taper of approximately 2%, and Nos. 20 and 25 with a shank taper of approximately 4%. 
         [0089]    Sandblasted instruments with superficial grooves with slightly cutting edges, have provided good penetration results, namely in engraving a cutting adjacent to the fractured instrument without encroaching with the coils of the fractured instrument, and in removing the dentine of the root canal. Optimal penetration results have been obtained with instruments that are sandblasted with aluminum oxide. 
         [0090]    Second (2 nd ) Class: Instruments for Catheterization 
         [0091]    This class includes hand operated instruments having a series of horizontally, vertically, or transversally striated deep grooves with cutting edges, that are separated by restricted smooth or sandblasted areas or even instruments that are completely sandblasted. As used herein, the term “deep” denotes a general depth that ranges between approximately between 0.12 mm and 0.8 mm. The instruments in this class include a generally circular cross section, and a conical tip that may be cutting or non-cutting. 
         [0092]    The shanks of these instruments range from No. 6 to 20. The shanks may be made from stainless steel, and range from No. 6 to 20. The shanks may alternatively be made from NiTi, and range from No. 20 to 40. The shafts of all these instruments have a taper of approximately 0%, 1%, 2%, and 4%, and a length that ranges from approximately 12 mm to 32 mm ( FIG. 6 ). The preferred embodiments of the instruments in this class that provide optimal results are those made of stainless steel with Nos. 10, 15, and 20, with an approximate 2% taper. These preferred embodiments include instruments that are made from NiTi, No. 20, with an approximate 4% shank taper. 
         [0093]    The instruments of this 1 st  category will now be described with reference to  FIGS. 1 through 6 .  FIG. 1A  is a schematic illustration of an exemplary hand operated instrument (or file)  100  for use as a first category, first class instrument, according to a preferred embodiment of the present invention. The instrument  100  generally includes an elongated, tapered shank  105  with superficial horizontally striated grooves  110  with slightly cutting edges that are separated by smooth areas  111 . 
         [0094]    In one exemplary embodiment, the grooves  110  form horizontal linear striations that are approximately 1 mm wide. It should be understood that the grooves  110  might assume other different patterns. The width of each smooth area  111  varies between approximately 2 mm and 3 mm. 
         [0095]    The instrument  100  further includes a tip  120  and a handle  125 . The tip  120  may be cutting or non-cutting, beveled or non beveled, depending on the desired application. The handle  125  secures one end of the shank  105 , and enables an endodontist to safely and ergonomically hold the instrument  100  while performing the treatment. It should be understood that the instrument  100  may alternatively be electrically rotating, in which case, the handle  125  is replaced with an appropriate handle or interface that connects the shank  105  to an external rotary source (not shown), as is known or available in the field. 
         [0096]    The shank  105  can be made of any suitable material, including but not limited to stainless steel or NiTi (Nickel Titanium). The shank  105  may have a constant or variable taper along its axial length, ranging from approximately 0% to 4%, a length ranging from approximately 12 mm to 32 mm, and a width ranging from approximately No. 10 to 25. 
         [0097]      FIG. 1B  illustrates another instrument  150  for use as a first category, second class instrument according to a preferred embodiment of the present invention. The instrument  150  may also be used as a second or third category instrument, as explained herein. 
         [0098]    The instrument  150  is generally similar in design and construction to the instrument  100  of  FIG. 1A , and comprises an elongated, tapered shank  155  with deep horizontally striated grooves  160  with cutting edges that are separated by restricted smooth areas  161 . In one exemplary embodiment, the grooves  160  form horizontal linear striations that are approximately 2 to 3 mm wide. It should be understood that the grooves  160  might assume other patterns. The width of each smooth area  161  is approximately 1 mm. 
         [0099]    The instrument  150  further includes a cutting or non-cutting tip  120  and a handle  125 , whose design and function are explained earlier in connection with the instrument  100 . 
         [0100]    It should be understood that these instruments  100 ,  150  can be modified, as explained herein, for use as electrically rotating instruments. 
         [0101]      FIG. 2  respectively illustrates two exemplary hand operated instruments  200  ( FIG. 2A ) and  250  ( FIG. 2B ) that are generally similar in design and construction to the instruments  100 ,  150  (respectively) of  FIG. 1 . It should be understood that these instruments  200 ,  250  can be modified, as explained herein, for use as electrically rotating instruments. 
         [0102]    The instrument  200  can be used as a first category, first class instrument. It includes an elongated, tapered shank  205  with superficial vertically striated grooves  210  with slightly cutting edges that are separated by smooth areas  211 , according to a preferred embodiment of the present invention. In one exemplary embodiment, the grooves  210  form vertical linear striations that are approximately 1 mm in width. The smooth areas  211  separate the grooves  210  at a distance of approximately 2 to 3 mm. 
         [0103]    The instrument  200  further includes a cutting or non-cutting tip  220  and a handle  125 , which are respectively similar to the tip  120  and handle  125  of the instrument  100  of  FIG. 1A . 
         [0104]    The instrument  250  of  FIG. 2B  can be used as a first category, second class instrument, according to a preferred embodiment of the present invention. It may also be used as a second or third category instrument, as explained herein. The instrument  250  includes an elongated, tapered shank  255  having deep vertically striated grooves  260  with cutting edges that are separated by restricted smooth areas  261 . In one exemplary embodiment, the grooves  260  form vertical linear striations that are approximately 2 to 3 mm in width. The smooth areas  261  separate the grooves  260  at a distance of approximately 1 mm. 
         [0105]    The instrument  250  further includes a cutting or non-cutting tip  220  and a handle  125 , which are respectively similar to the tip  120  and handle  125  of the instrument  150  of  FIG. 1B . 
         [0106]      FIG. 3  respectively illustrates two exemplary hand operated instruments  300  ( FIG. 3A ) and  350  ( FIG. 3B ) that are generally, respectively similar in design and construction to the instruments  100 ,  150  of  FIG. 1 and 200, 250  of  FIG. 2 . It should be understood that these instruments  300 ,  350  can be modified, as explained herein, for use as electrically rotating instruments. 
         [0107]    The instrument  300  can be used as a first category, first class instrument. It includes an elongated, tapered shank  305  with superficial transversally striated grooves  310  with slightly cutting edges that are separated by smooth areas  311 , according to a preferred embodiment of the present invention. In one exemplary embodiment, the grooves  310  form transversally linear striations that are approximately 1 mm in width. The smooth areas  311  separate the grooves  310  at a distance of approximately 2 mm to 3 mm. 
         [0108]    The instrument  300  further includes a cutting or non-cutting tip  320  and a handle  125 , which are respectively similar to the tip  120  and handle  125  of the instrument  100  of  FIG. 1A . 
         [0109]    The instrument  350  of  FIG. 3B  can also be used as a first category, second class hand operated instrument, according to a preferred embodiment of the present invention. It may also be used as a second or third category instrument, as explained herein. The instrument  350  includes an elongated, tapered shank  355  with deep transversally striated grooves  360  with cutting edges that are separated by restricted smooth areas  361 . In one exemplary embodiment, the grooves  360  form transversally linear striations that are approximately 2 to 3 mm in width. The smooth areas  361  separate the grooves  360  at a distance of approximately 1 mm. 
         [0110]    The instrument  350  further includes a cutting or non-cutting tip  320  and a handle  125 , which are respectively similar to the tip  120  and handle  125  of the instrument  150  of  FIG. 1B . 
         [0111]      FIG. 4  illustrates an exemplary hand operated instrument  400  that is generally similar in design and construction to the instrument  300  of  FIG. 3A . It should be understood that the instrument  400  can be modified, as explained herein, for use as an electrically rotating instrument. 
         [0112]    The instrument  400  can be used as a first category, first class instrument. It includes an elongated, tapered shank  405  with superficial transversally striated grooves  410  with slightly cutting edges that are separated by smooth areas  411 , according to a preferred embodiment of the present invention. In one exemplary embodiment, the grooves  410  form short, transversally linear striations that are approximately 1 mm in width. The distance between two consecutive grooves  410  may be adjusted so that it can be either fixed or variable, along the axial length of the shank  405 . As an example only, the separation of the grooves  410  (which constitutes the width of the smooth areas  411 ) can vary between approximately 2 mm and 3 mm. 
         [0113]    The instrument  400  further includes a pointed, beveled cutting tip  420  and a handle  125 . 
         [0114]      FIG. 5  illustrates an exemplary hand operated instrument  500  that is generally similar in design and construction to the instrument  300  of  FIG. 3A . It should be understood that the instrument  500  can be modified, as explained herein, for use as an electrically rotating instrument. 
         [0115]    The instrument  500  can be used as a first category, first class instrument. It includes an elongated, tapered shank  505  with superficial transversally striated grooves  510  with slightly cutting edges that are separated by roughened areas  511 , according to a preferred embodiment of the present invention. In one exemplary embodiment, the grooves  510  form short, transversally linear striations. 
         [0116]    In a most preferred embodiment, the roughened areas  511  are formed by sandblasting. The instrument  500  further includes a cutting or non-cutting tip  520  and a handle  125 . 
         [0117]      FIG. 6  illustrates an exemplary hand operated instrument  600  that is generally similar in design and construction to the instrument  350  of  FIG. 3B . It should be understood that the instrument  600  can be modified, as explained herein, for use as an electrically rotating instrument. 
         [0118]    The instrument  600  can be used as a first category, second class instrument. It includes an elongated, tapered shank  605  with deep transversally striated grooves  610  with cutting edges that are separated by restricted smooth areas  611 , according to a preferred embodiment of the present invention. In one exemplary embodiment, the grooves  610  form short, transversally linear striations that are approximately 2 to 3 mm in width. The separation distance between the grooves  610  may be adjusted so that it can be either fixed or variable, along the axial length of the shank  605 . As an example only, the separation of the grooves  610  (which constitutes the width of the smooth areas  611 ) is 1 mm. 
         [0119]    The instrument  600  further includes a pointed, cutting or non-cutting tip  620  and a handle  125 . 
         [0120]    2 nd  Category: Instruments for Penetrating Fine and Curved Root Canals 
         [0121]    As illustrated in  FIG. 7 , this category comprises electrically operated rotating instruments (e.g.,  700 ) that are preferably (but not exclusively) made for example of NiTi, from No. 10 to 20, with a shank  705  having a taper of approximately 2%. Although the illustrated instrument  700  is shown to include a series of transversal, deep, striated grooves  710  with cutting edges, it should be understood that other embodiments can alternatively include a series of horizontally or vertically striated, deep grooves with cutting edges, that are separated by either smooth or roughened (i.e., sandblasted) restricted areas  711 , or even instruments that are completely sandblasted. 
         [0122]    The shank  705  of the instrument  700  has a generally circular cross-section, and a conical cutting or non-cutting tip  720 , with a length ranging from approximately 21 to 32 mm. The circular cross section and conical tip  720  of the shank  705  helps create a space around the segment(s) of the fractured instruments that are lodged within the root canal, thus enabling the instruments of the 1 st  category, 1 st  class, to bypass the lodged fractured segment(s). 
         [0123]    A handle  725  secures the shank  705  to an external motorized source (not shown). 
         [0124]    3 rd  Category: Instruments which May be Used for Enlarging and Shaping Root Canals 
         [0125]    As illustrated in  FIG. 8 , this category comprises electrically operated rotating instruments (e.g.,  800 ) made of NiTi from No. 20 to 40, with a shank  805  having a generally circular cross section. Although the illustrated instrument  800  is shown to include a conical cutting or non-cutting tip  820 , with a series of saw teeth  810  that are separated by restricted smooth areas  811 , it should be understood that other embodiments can further include horizontally, vertically, or transversally striated grooves. 
         [0126]    The saw teeth configuration expels the dental debris from the root canal and lessens the rubbing force of the instrument on the walls of the root canal, especially when using files from Nos. 20 to 40, thus avoiding root canal cracks. 
         [0127]    The taper of the shank  805  ranges from approximately 4% to 10%, and has a length of approximately 21 mm to 32 mm. 
         [0128]    It is important to note that the shanks of the instruments in all the foregoing three categories may or may not be sandblasted. It is also noteworthy to indicate that the instruments of the above three categories successfully penetrate root hypercalcifications that are formed in the root canal. In addition, a file instrument No. 20 with a 4% taper, and a file instrument No. 17 with a 4% taper, have shown remarkable utility in creating a space around fractured, lodged fragments of previously used instruments, so that the instruments of the 1 st  category, 1 st  class, may be used in order to bypass these fractured instruments. 
         [0129]    Alternative embodiments that are contemplated by the present invention include but are not limited to the following hand operated and electrically operated instruments: 
         [0130]      FIGS. 9A, 9B  illustrate an electrically operated instrument  900  and a manually operated instrument  950  that is generally similar in design and function to the electrically operated instrument  900 , and therefore only one instrument will be described in detail. The electrically operated instrument  900  generally includes an elongated, tapered shank  905  that defines an upper cylindro-conical section  910  and a spirally (or helically) shaped lower section  915 . 
         [0131]    The cylindro-conical section  910  includes at its upper end, a tip  920  that may be cutting or non-cutting, depending on the desired application. While in this particular illustration the cylindro-conical section  910  is illustrated as being a roughened surface, it should be understood that the cylindro-conical section  910  could include striated grooves with cutting edges separated by smooth or sandblasted areas. The length of the shank  905  preferably ranges between approximately 12 mm and 32 mm, and its width preferably varies from No. 10 to 40. The taper of the instrument preferably ranges from approximately 2% to 10%. In a preferred embodiment, the entire shank  905  of the instrument  900  is sandblasted. 
         [0132]    Section  910  is intended to penetrate root canal blockages while section  915  serves to debride and to shape the opened path. 
         [0133]    The instrument  900  further includes a handle  925  that secures one end of the shank  905 , and that enables an endodontist to connect the instrument  900  to an external rotary source (not shown) as is known or available in the field. Similarly, the instrument  950  further includes a manual handle  955  that secures one end of the shank  905 , and that enables an endodontist to safely and ergonomically hold the instrument  950  while manually performing the treatment. 
         [0134]      FIGS. 10A, 10B  illustrate an electrically operated instrument  1000 , and a manually operated instrument  1050  that is generally similar in design and function to the electrically operated instrument  1000 , and therefore only one instrument will be described in detail. The electrically operated instrument  1000  generally includes an elongated, tapered shank  1005  that defines a plurality of roughened cylindro-conical sections  1010 ,  1011 ,  1012 , that are separated by a plurality of spirally (or helically) shaped sections  1015 ,  1016 . 
         [0135]    The cylindro-conical section  1010  of the instrument  1000  comprise striated grooves with cutting edges separated by smooth or sandblasted areas and further includes at its forwardmost end, a tip  1020  that may be cutting or non-cutting, depending on the desired application. The length of the shank  1005  ranges from approximately 12 mm to 32 mm, and its width preferably varies from No. 10 to 40. The taper of the instrument preferably ranges from approximately 2% to 10%. In a preferred embodiment, the whole instrument will be sandblasted. 
         [0136]    Section  1010  is intended to penetrate root canal blockages while section  1015  serves to debride and to shape the opened path. 
         [0137]    The instruments illustrated in  FIG. 10  provide better penetration results than the instruments in  FIG. 9 . They are preferred in case of hard hypercalcifications and resistant paste. 
         [0138]      FIGS. 11A, 11B  respectively illustrate an electrically operated instrument  1100 , and a manually operated instrument  1150  that is generally similar in design and function to the electrically operated instrument  1100 , and therefore only one instrument will be described in detail. The electrically operated instrument  1100  generally includes an elongated, tapered shank  1105  that defines a plurality of roughened cylindro-conical sections  1110 ,  1111 , which are separated by a plurality of spirally (or helically) shaped sections  1115 ,  1116 ,  1117 . 
         [0139]    The spiral section  1115  of the instrument  1100  further includes at its forwardmost end, a tip  1120  that may be cutting or non-cutting, depending on the desired application. The length of the shank  1105  ranges from approximately 12 mm to 32 mm, and its width preferably varies from No. 10 to 40. The taper of the instrument preferably ranges from approximately 2% to 10%. 
         [0140]    In the exemplary embodiment of  FIG. 11 , the cylindro-conical sections  1110 ,  1111  may be striated with groves with cutting edges separated by smooth or sandblasted areas. In a preferred embodiment, the whole instrument will be sandblasted. 
         [0141]      FIGS. 12A, 12B  illustrate yet other alternative embodiments of an electrically operated instrument  1200  and a manually operated instrument  1250 , that are respectively, generally similar in design and function to the instruments  1000 ,  1050  of  FIGS. 10A, 10B . 
         [0142]    The electrically operated instrument  1200  generally includes an elongated, tapered shank  1205  that defines a plurality of roughened cylindro-conical sections  1210 ,  1211 ,  1212 , that are separated by a plurality of spirally (or helically) shaped sections  1215 ,  1216 . The cylindro-conical section  1210  of the instrument  1200  further includes at its forwardmost end, a tip  1220  that may be cutting or non-cutting, depending on the desired application. The length of the shank  1205  ranges from approximately 12 mm to 32 mm, and its width preferably varies from No. 10 to 40. The taper of the instrument preferably ranges from approximately 2% to 10%. 
         [0143]    In the exemplary embodiment of  FIG. 12 , the cylindro-conical sections  1210 ,  1211 ,  1212  may be striated with groves with cutting edges separated by smooth or sandblasted areas while the spiral sections may be similarly sandblasted. 
         [0144]    Having described the exemplary instruments embodied by the present invention, the methods of using these instruments will now be described in more detail, in connection with the drawings, particularly  FIGS. 13 through 18 . 
         [0145]    Methods of Using the Instruments in Treating Root Canals 
         [0146]    The new root canal treatment method generally aims to bypass root obstructions resulting from fractured instruments and to penetrate hypercalcification, to bypass dental shoulders, to penetrate resistant paste, curved root canals and other obstructions resulting from a previous root treatment. More specifically, the following exemplary treatment methods will now be described in more detail: 
         [0000]    I—Method of treating a root canal that does not exhibit signs of a resistive path, obstruction, or blockage.
 
II—Method of bypassing root obstructions resulting from fractured instruments.
 
III—Method of penetrating root obstructions resulting from hypercalcification.
 
IV—Method of penetrating root obstructions resulting from curved root canals.
 
V—Method of bypassing root obstructions resulting from a shoulder.
 
VI—Method of penetrating root obstructions resulting from a previous root canal treatment.
 
         [0147]    I—Method of Treating a Root Canal that does not Exhibit Signs of a Resistive Path, Obstruction, or Blockage 
         [0148]      FIG. 13  comprises  FIGS. 13A, 13B, 13C, and 13D  and illustrates an exemplary tooth  1300  that does not exhibit signs of a resistive path, obstruction, or blockage. With further reference to  FIG. 18 , an endodontic treatment method  1800  is performed according to the following steps: 
         [0149]    As illustrated in  FIG. 13A , the endodontist starts at step  1810  of  FIG. 18 , to enlarge the root canal  1312  by selectively and sequentially using the instruments (denoted with numeral reference  1320 ) of the 1 st  category, 2 nd  class (e.g.,  FIGS. 1B, 2B, 3B and 6 ), starting for example with a manual instrument No. 8 having an approximate 2% taper, in increasing order to No. 15 with an approximate 2% taper (1 st  category, 2 nd  class), exerting a manual force with a clockwise 90-degree rotation along the arrow F, in order to reach the apex  1333  of the root canal  1312 . 
         [0150]    As illustrated at step  1820  of  FIG. 18 , the endodontist further enlarges the root canal  1312  using for example, an electrically rotating instrument (denoted with numeral reference  1330 ) selected from the 2 nd  category (e.g.,  FIG. 7 ), starting with No. 10 having an approximate 2% taper, in an increasing order to No. 20, along the arrow F in order to reach the apex of the root canal  1333 . 
         [0151]    As illustrated at step  1830  of  FIG. 18  and in  FIG. 13B , the endodontist continues to enlarge the root canal  1312  using for example, an electrically rotating instrument  1320 , which is selected from the 3rd category (e.g.,  FIG. 8 ), starting with an instrument from No. 20 to No. 25 with an approximate 4% taper to No. 25 with an approximate 6% taper whenever possible, in order to reach the apex  1333  of the root canal  1312 . In a preferred embodiment, an instrument with No. 20 having an approximate 4% taper can be used. 
         [0152]    As illustrated at step  1840  and also in  FIG. 13C , upon completion of step  1830  as described earlier, the endodontist clears the widened root canal  1312  of any debris, as is known in the field, in preparation for the final obturation step. 
         [0153]    As illustrated at step  1850  and also in  FIG. 13D , the endodontist obturates the root canal  1312  with the appropriate filling material  1350 , as is known in the field. 
         [0154]    II—Method of Bypassing Root Obstructions Resulting from Fractured Instruments 
         [0155]    With reference to  FIG. 14 , it comprises  FIGS. 14A, 14B, 14C, 14D, 14E , and  14 F, and illustrates an exemplary tooth  1400  having a root canal  1412  within which an obstruction, such as a fragment  1410  of a fractured instrument (such as a file) is lodged by a previous root canal treatment. With further reference to  FIGS. 19A and 19B , the treatment method  1900  is performed according to the following steps: 
         [0156]    As further illustrated in  FIG. 14A , at step  1910  of  FIG. 19A , the endodontist enlarges the root canal  1412  by selectively and sequentially using the instruments (denoted with numeral reference  1420 ) of the 1 st  category, 2 nd  class (e.g.,  FIGS. 1B, 2B, 3B and 6 ), starting for example with a manual instrument No. 8 having an approximate 2% taper, in increasing order to No. 15 with an approximate 2% taper (1 st  category, 2 nd  class), exerting a manual force with a clockwise 90 degrees rotation in along the arrow F, in order to reach the fractured instrument  1410  of the root canal  1412 . 
         [0157]    As illustrated at step  1920  of  FIG. 19A  and also in  FIG. 14B , the endodontist further enlarges the root canal  1412  using for example, an electrically rotating instrument (denoted with numeral reference  1430 ) selected from the 2 nd  category (e.g.,  FIG. 7 ), starting with No. 10 having an approximate 2% taper, in an increasing order to No. 20, in order to reach the fractured instrument in the root canal  1412 . 
         [0158]    As illustrated at step  1930  of  FIG. 19A  and also in  FIG. 14B , the endodontist continues to enlarge the root canal  1412  using for example, an electrically rotating instrument (denoted with numeral reference  1430 ) selected from the 3 rd  category (e.g.,  FIG. 8 ), starting with an instrument from No. 20 to No. 25 with an approximate 4% taper to No. 25 with an approximate 6% taper whenever possible. In a preferred embodiment, an instrument with No. 20 having an approximate 4% taper can be used to reach the fractured instrument in the root canal  1412 . 
         [0159]    For relatively simple cases, each new instrument (whether manual or electrically operated) is capable of bypassing the obstruction after enlarging the root canal  1412  according to above steps  1910 ,  1920 , and  1930 . 
         [0160]    However, for more complex cases, and as illustrated by step  1940  of  FIG. 19A  and  FIG. 14C , the endodontist resumes process  1900  by engraving a cutting  1444  beside the obstruction  1410 , using new manual instruments, selected for example from the 1 st  category, 1 st  class, and preferably made of NiTi, No. 20, with an approximate 4% taper and a cutting tip (e.g.,  120 ,  220 ,  320 ,  520  or eventually  420 ). The endodontist starts by exerting a manual force with a clockwise 90-degree rotation, and then withdraws the instrument by exerting an anti-clockwise rotation of the same angle, along the rotational arrow M. The relatively large cross sectional surface of the cutting tip  120 ,  220 ,  320 ,  520  or eventually  420  avoids opening a false canal when exerting a relatively high manual force. 
         [0161]    The endodontist then enlarges the cutting  1444  into an initial path using a manual instrument (also denoted by the numeral reference  1440 ) selected for example from the 1 st  category, 1 st  class, and preferably made of NiTi, No. 20 with an approximate 4% taper and a non-cutting tip (e.g.  1633  B), exerting a manual force with a clockwise 90 degrees rotation along the arrow F, in order to preserve the initial path  1444 . 
         [0162]    As further illustrated in  FIG. 14D , and in order to further penetrate the obstructed canal through the opened initial path  1444 , the endodontist uses, at step  1960  of  FIG. 19B , a manual instrument  1450  selected for example from the 1 st  category, 1 st  class, and preferably made of stainless steel, No. 20, having an approximate 2% taper with a cutting tip (e.g.,  1633  A), for engraving a new cutting  1445 , adjacent to the obstruction  1410 , exerting a manual force with a clockwise 90-degree rotation along the arrow F. 
         [0163]    Thereafter, the endodontist preferably uses, at step  1970  of  FIG. 19B , to manually enlarge the newly opened cutting  1445  using an instrument (still denoted by  1450 ) selected for example from the 1 st  category, 1 st  class, and preferably made of stainless steel, No. 20, having an approximate 2% taper with a non-cutting tip (e.g.,  1633  B). 
         [0164]    The endodontist continues to enlarge the new path  1445  using a manual instrument (still denoted by  1450 ) selected for example from the 1 st  category, 1 st  class, and preferably made of NiTi, No. 20, having an approximate 4% taper with a cutting tip (e.g.,  1633  A), followed by No. 20 having an approximate 4% taper with a non-cutting tip (e.g.,  1633  B), in order to preserve the new path  1445 . 
         [0165]    In case the endodontist encounters difficulty in penetrating the root canal  1412 , and whenever suitable, the endodontist may use a manual instrument  1440  ( FIG. 14C ) selected for example from the 1 st  category, 1 st  class, and preferably made of stainless steel, No. 20, having an approximate 2% taper with a cutting tip (e.g.,  1633  A), followed by No. 20 having an approximate 2% taper with a non-cutting tip (e.g.,  1633  B). 
         [0166]    Alternatively, the endodontist may use a manual instrument  1450  ( FIG. 14D ) selected for example from the 1 st  category, 1 st  class, and preferably made of stainless steel, No. 15, having an approximate 2% taper with a cutting tip (e.g.,  1633  A) in order to create a new cutting. This step is then followed by the use of a manual instrument selected for example from the 1 st  category, 1 st  class, and preferably made of stainless steel, No. 15, having an approximately 2% taper with a non-cutting tip (e.g.,  1633  B), in order to preserve the newly opened path  1445 . 
         [0167]    In the event the instruments that are collectively referenced by  1450  fail to open or enlarge the required path  1445 , the endodontist uses a smaller instrument preferably made of stainless steel, in the same sequence as described above, until the apex  1466  of the root canal  1412  is reached (step  1980 ), as follows: The path  1445  is enlarged manually, at step  1970 , using sequentially hand operated stainless steel instruments with cutting and non-cutting tips from No. 8 or 10 until No. 20 of approximately 2% taper (1 st  category 1 st  class). The introduction of the instrument with a cutting tip is followed by the use of the same instrument with a non-cutting tip. Alternatively, use may be made of NiTi instrument  1450 , No. 20 with an approximate 4% taper (1 st  category, 1 st  class), first with instrument  1450  having a cutting tip (e.g.,  1633  A), then with instrument  1450  having a non-cutting tip (e.g.,  1633  B). 
         [0168]    The endodontist starts at step  1980  with electrically operated instruments of the 1 st  category, 1 st  class, which are preferably made of NiTi, and having a non-cutting tip (e.g.,  1633  B), in an increasing order starting by using instrument no. 10 with approximately 2% taper until reaching No. 20 of approximately 2% taper. 
         [0169]    Then, the endodontist continues with electrically operated instruments of the 2 nd  category, which are preferably made of NiTi, and having a non-cutting tip (e.g.,  1633  B), in an increasing order instruments from No. 20 to No. 25 having approximately 2% taper. 
         [0170]    Finally, the endodontist completes the enlargement of the path  1445  with electrically operated instruments of the 3 rd  category, which are preferably made of NiTi, and having a non-cutting tip (e.g.,  1633  B), namely instrument No. 20 or 25 having approximately 4% taper. 
         [0171]    It should be noted that the use of files (or instruments) having a beveled tip is recommended only in case the aforesaid instruments fail to engrave a cutting or path adjacent to the fractured instrument  1410 , particularly in case of difficult hypercalcification cases or in the case the cross section of the fractured instrument  1410  is relatively large. 
         [0172]    As illustrated at step  1990  and also in  FIG. 14E , upon completion of step  1980  as described earlier, the endodontist clears the widened root canal  1445  of any debris, as is known in the field, in preparation for the final obturation step. 
         [0173]    As illustrated at step  1999  and also in  FIG. 14F , the endodontist obturates the root canal  1445  with the appropriate filling material  1446 , as is known in the field. It should be noted that the obturation may be performed with or without removing the fragment  1410  of the fractured instrument. 
         [0174]    Although the conventional art describes that the use of electrically operated files may not be proper in case of treating dental roots with fractured instruments  1410 , the present invention teaches that it is possible to directly reach the apex  1466 , at step  1999 , by using electrically operated instruments with non-cutting tips, made of NiTi, after step  1970 , in an increasing order from No. 10 with an approximate 2% taper (selected from the 1 st  category, 1 st  class) to No. 20 with an approximate 4% taper (selected from the 1 st  category, 1 st  class), followed by the sequential use of instruments selected from the 2 nd  and 3 rd  categories, as deemed appropriate by the endodontist. 
         [0175]    Alternatively, the present invention teaches that in less difficult cases, it is possible from step  1950  to directly reach the apex  1466 , step  1999 , by using electrically operated instruments with non-cutting tips, made of NiTi, starting by enlarging the initial path  1444  with No. 20 having an approximate 4% taper (1 st  category, 1 st  class); then using in an increasing order NiTi instruments with non-cutting tip from No. 10 with an approximate 2% taper (selected from the 1 st  category, 1 st  class) to No. 20 with an approximate 4% taper (selected from the 1 st  category, 1 st  class), followed sequentially by instruments selected from the 2 nd  and 3 rd  categories, as deemed appropriate by the endodontist. 
         [0176]    It is worth noting that the root canal is irrigated with sodium hypochloride and EDTA (Ethylenediaminetetraacetic acid) at each relevant step of process  1900 . 
         [0177]    The following X-Rays  FIGS. 23A, 23B, 23C, 24A, 24B, 24C, 25A, 25B, 25C, 25D, 26A, 26B, 27A, 27B, 27C, 28A, 28B, 28C, 28D, 29A, 29B ,  29 C,  30 A,  30 B,  31 A,  31 B,  32 A,  32 B,  32 C,  33 A,  33 B,  33 C,  33 D,  34 ,  35 ,  36 A,  36 B,  36 C,  37 A,  37 B,  38 A, and  38 B provide supporting illustrations of this novel process  1900 : 
         [0178]      FIG. 23A  shows a broken file in tooth no. 26 blocking the totality of the root canal.  FIG. 23B  shows the bypassing of the broken file and reaching the apex with the new instrument according to the present invention.  FIG. 23C  shows the fully hermetic obturation of the treated root canal. 
         [0179]      FIG. 24A  shows a broken file in tooth no. 46 blocking the totality of the root canal.  FIG. 24B  shows the bypassing of the broken file and the piercing of the hypercalcification and reaching the apex with the new instrument according to the present invention.  FIG. 24C  shows the fully hermetic obturation of the treated root canal. 
         [0180]      FIG. 25A  shows a hypercalcification, a shoulder, and a broken file in the mesial canals of tooth no. 36.  FIG. 25B  shows the broken file.  FIG. 25C  shows the bypassing of the broken file, the penetration of the shoulder and the piercing of the hypercalcification in the 2 nd  mesial canal and reaching the apex with the new instrument, according to the present invention.  FIG. 25D  shows the fully hermetic obturation of the treated root canal. 
         [0181]      FIG. 26A  shows two fractured files in the mesio vestibular canal in tooth no. 46, blocking the totality of the root canal.  FIG. 26B  shows the bypassing of the two broken files and reaching the apex with the new instrument according to the present invention. 
         [0182]      FIG. 27A  shows three broken files in tooth no. 35 blocking the totality of the root canal.  FIG. 27B  shows the bypassing of the three broken files and reaching the apex with the new instrument according to the present invention.  FIG. 27C  shows the fully hermetic obturation of the root canal. 
         [0183]      FIG. 28A  shows a broken file in tooth no. 47 blocking the totality of the root canal due to hypercalcification.  FIG. 28B  shows a cutting made with the new instrument according to the invention, and a second broken file.  FIG. 28C  shows the bypassing of the two broken files and the piercing of the hypercalcification and reaching the apex with the new instrument according to the present invention.  FIG. 28D  shows the fully hermetic obturation of the treated root canal. 
         [0184]    More specifically, and as a comparative illustration, instead of using the new instruments according to the invention, a conventional file was used to enlarge the cutting and to bypass the broken file. However, the conventional file was broken, as expected, while the new instrument according to the invention has successfully bypassed the two broken files, pierced the hypercalcification, and reached the apex, without making a false canal ( FIG. 28C ). 
         [0185]      FIG. 29A  shows two superposed broken files in tooth no. 26 blocking the third apical of the root canal.  FIG. 29B  shows the bypassing of the broken files and reaching the apex with the new instrument according to the present invention.  FIG. 29C  shows the fully hermetic obturation of the treated root canal. 
         [0186]      FIG. 30A  shows a broken file in tooth no. 37 blocking the third apical of the root canal.  FIG. 30B  shows the bypassing of the broken file and reaching the apex with the new instrument according to the present invention. 
         [0187]      FIG. 31A  shows a false canal and two broken files in tooth no. 36 blocking the apex of the root canal.  FIG. 31B  shows the avoidance of the false canal and the bypassing of the broken file and reaching the apex with the new instrument according to the present invention. 
         [0188]      FIG. 32A  shows a broken file in the third apical of the mesial canal tooth no. 46 blocking the apex.  FIG. 32B  shows the bypassing of the broken file and reaching the apex with the new instrument according to the present invention.  FIG. 32C  shows the fully hermetic obturation of the treated root canal. 
         [0189]    III—Method of Penetrating Root Obstructions Resulting from Hypercalcification 
         [0190]    With reference to  FIG. 15 , it comprises  FIGS. 15A, 15B, and 15C  and illustrates an exemplary tooth  1500  having a root canal  1512  that is blocked or obstructed by hypercalcification  1510 . With further reference to  FIGS. 20A, 20B , the treatment method  2000  is performed according to the following steps: 
         [0191]    As further illustrated in  FIG. 15A , the endodontist enlarges, at step  2010  of  FIG. 20A , the root canal  1512  of the tooth  1500  by starting with a manual instrument selected from the 1 st  category, 2 nd  class, No. 8, with an approximate 2% taper, in an increasing order to an instrument selected from the 1 st  category, 2 nd  class, No. 15, with an approximate 2% taper, exerting a manual force with a clockwise 90-degree rotation along the arrow F, until the tip  1525  of the instrument  1520  reaches the hypercalcification  1510 . 
         [0192]    The endodontist then further enlarges, at step  2020 , the root canal  1512  using electrically rotating instruments  1520  selected from the 2 nd  category, starting with No. 10 with an approximate 2% taper, in an increasing order to No. 20 with an approximate 2% taper, until reaching the hypercalcification. 
         [0193]    Still at step  2020 , the endodontist continues to enlarge the root canal  1512  using electrically rotating new instruments that are selected from the 3 rd  category, using files from No. 20 to No. 25 with an approximate 4% taper, to No. 25 with an approximate 6% taper whenever possible. Preferred results were obtained with a No. 20 instrument with an approximate 4% taper, until reaching the hypercalcification  1510 . 
         [0194]    The endodontist then starts piercing the hypercalcification  1510  at step  2030 , to form an initial path  1555  therewithin, using manual NiTi instruments  1530  selected from the 1 st  category, 1 st  class, No. 20 with an approximate 4% taper, and a cutting tip  1525 . The endodontist exerts a manual force with a clockwise 90-degree rotation. The endodontist then withdraws the instrument  1530  by exerting an anti-clockwise rotation of the same angle. The relatively large cross-sectional surface of the cutting tip  1525  avoids opening a false canal when exerting a relatively high manual force. 
         [0195]    The endodontist continues at step  2040  by enlarging the initial path  1555 , using a manual NiTi instrument that is selected from the 1 st  category, 1 st  class, No. 20 having an approximate 4% taper with a non-cutting tip (e.g.,  1633  B), in order to preserve the opened initial path  1555 . 
         [0196]    The endodontist then continues to step  2050 , in order to enlarge the initial path  1555  and to pierce the remainder of the hypercalcification, by using a manual stainless steel instrument selected from the 1 st  category, 1 st  class, No. 20, with an approximate 2% taper and a cutting tip  1525 . It is recommended to continue to manually enlarge the initial path  1555  using a manual stainless steel instrument selected from the 1 st  category, 1 st  class, No. 20 with an approximate 2% taper and a non-cutting tip (e.g.,  1633  B). 
         [0197]    At step  2060 , the endodontist further enlarges the initial path  1555  by first using a manual NiTi instrument selected from the 1 st  category, 1 st  class, No. 20, with an approximate 4% taper and a cutting tip  1555 , and then using a manual NiTi instrument also selected from the 1 st  category, 1 st  class, No. 20, with an approximate 4% taper and a non-cutting tip (e.g.,  1633  B), so as to preserve the initial path  1555 . 
         [0198]    In the event the endodontist encounters difficulty in penetrating the root canal  1512 , manual stainless steel instrument  1540  selected from the 1 st  category, 1 st  class, No. 20, with an approximate 2% taper and a cutting tip  1525  is used whenever feasible. Otherwise, the endodontist uses a manual stainless steel instrument  1540  selected from the 1 st  category, 1 st  class, No. 15, with an approximate 2% taper and a cutting tip  1525 , in order to pierce a new path that is adjacent to the initial path  1555 . This step is followed by the use of a manual stainless steel instrument  1540  selected from the 1 st  category, 1 st  class, No. 15, with an approximate 2% taper and a non-cutting tip, in order to preserve the new adjacent path. In case the instruments  1540  fail to open the required path, the endodontist uses smaller stainless steel instruments in the same sequence until reaching the apex  1566  of the root canal  1512  ( FIG. 15C ). 
         [0199]    Once the initial path  1555  is enlarged, at step  2060 , the initial path  1555  is gradually enlarged manually using sequentially hand operated stainless steel instruments with cutting and non-cutting tips from No. 8 or 10 until No. 20 of approximately 2% taper (1 st  category 1 st  class). The introduction of the instrument with a cutting tip is followed by the use of the same instrument with a non-cutting tip. Alternatively, if possible, a NiTi instrument also selected from the 1 st  category, 1 st  class, No. 20 with an approximate 4% taper and a cutting tip  1525  followed by the same instrument with a non-cutting tip (e.g.,  1633  B), may be introduced. 
         [0200]    Once the initial path  1555  has been enlarged to the desired dimensions, the endodontist then uses, at step  2070 , electrically operated NiTi instruments  1540  selected from the 1 st  category, 1 st  class, and instruments of the 2 nd  category, with a non-cutting tip (e.g.,  1633  B), followed by the use of instruments  1540  of the 3 rd  category, with a non-cutting tip. In performing this step  2070 , the endodontist sequentially uses in increasing order the instruments  1540  starting with instruments selected from the 1 st  category, 1 st  class, No. 10 to No. 20 with an approximate 2% taper, and then, instruments from No. 20 to No. 25 of approximately 2% taper of the 2 nd  category and finally instrument No. 20 or 25 with an approximate 4% taper of the 3 rd  category at the apex  1566 . 
         [0201]    As illustrated at step  2080  and also in  FIG. 14E , upon completion of step  2070  as described earlier, the endodontist clears the widened root canal of any debris, as is known in the field, in preparation for the final obturation step. 
         [0202]    As illustrated at step  2090  and also in  FIG. 14F , the endodontist obturates the root canal with the appropriate filling material  1446 , as is known in the field. 
         [0203]    According to the another embodiment of the present invention, it is possible to directly reach the apex  1566 , after step  2060 , by using electrically operated NiTi instruments selected from the 1 st  category, 1 st  class with a non-cutting tip (e.g.,  1633  B), in increasing order from No. 10 with an approximate 2% taper to No. 20 with an approximate 4% taper, followed by instruments of the 2 nd  and 3 rd  categories. 
         [0204]    According to yet another embodiment of the present invention, in less difficult cases, the endodontist may be able to directly reach the apex  1566 , after step  2040 , by using electrically operated NiTi instruments selected from the 1 st  category, 1 st  class with a non-cutting tip (e.g.,  1633  B), starting by enlarging the piercing with a No. 20 instrument having an approximate 4% taper. The process is resumed by using, in increasing order, instruments selected from the 1 st  category, 1 st  class, from No. 10 with an approximate 2% taper, to No. 20 with an approximate 4% taper of the 1 st  category, 1 st  class with a non-cutting tip, followed by non-cutting tip instruments of the 2 nd  and 3 rd  categories, as deemed appropriate by the endodontist. 
         [0205]    It is worth noting that the root canal is irrigated with sodium hypochloride and EDTA (Ethylenediaminetetraacetic acid) at each relevant step of process  2000 . 
         [0206]    The following X-Rays ( FIGS. 33 through 36 ) provide supporting illustrations of this novel process  2000 : 
         [0207]      FIG. 24A  shows a broken file in tooth no. 46 blocking the totality of the root canal.  FIG. 24B  shows the bypassing of the broken file and the piercing of the hypercalcification and reaching the apex with the new instrument according to the present invention.  FIG. 24C  shows the fully hermetic obturation of the treated root canal. 
         [0208]      FIG. 33A  shows an incomplete root treatment of tooth no. 35 due to hypercalcification blocking the third apical of the root canal.  FIGS. 33B, 33C , and  33 D show the piercing of the old resistant paste and progressively piercing the hypercalcification with the new instrument reaching the apex, according to the present invention. 
         [0209]      FIG. 34  shows a fully hermetic obturation of tooth no. 46 after piercing a hypercalcification and passing through an accentuated curved line. 
         [0210]      FIG. 35  shows a fully hermetic obturation of tooth no. 47 after piercing a hypercalcification and passing through an accentuated curved line. 
         [0211]      FIG. 36A  shows a false canal and an incomplete root treatment of tooth no. 35 due to hypercalcification blocking about half the root canal.  FIGS. 36B and 36C  show the progressive piercing of the hypercalcification with the new instrument reaching the apex, according to the present invention. 
         [0212]    IV—Method of Penetrating Root Obstructions Resulting from Curved Root Canals 
         [0213]    As illustrated in  FIG. 13 , the instruments of the present invention may be used to penetrate root obstructions resulting from curved root canals. In this event, the instruments of the 2 nd  category may be used followed by the instruments of the 3 rd  category, until the apex of the root canal is reached, with at least an instrument No. 20 having an approximate 4% taper. In case of difficulty, instruments selected from the 1 st  category, 2 nd  class are used, starting in increasing order from No. 8 to No. 15, with an approximate 2% taper followed by the instruments of the 2 nd  and 3 rd  categories. 
         [0214]    The following X-Rays ( FIGS. 34, 35 ) provide supporting illustrations of this novel process: 
         [0215]      FIG. 34  shows a fully hermetic obturation of tooth no. 46 after piercing a hypercalcification and passing through an accentuated curved line. 
         [0216]      FIG. 35  shows a fully hermetic obturation of tooth no. 47 after piercing a hypercalcification and passing through an accentuated curved line. 
         [0217]    V—Method of Bypassing Root Obstructions Resulting from a Shoulder 
         [0218]    With reference to  FIG. 16 , it comprises  FIGS. 16A, 16B, and 16C  and illustrates an exemplary tooth  1600  having a root canal  1612  that is obstructed by a shoulder  1610 . With further reference to  FIGS. 21A and 21B , the treatment method  2100  is performed according to the following steps: 
         [0219]    As further illustrated in  FIG. 16A , the endodontist enlarges at step  2110  of  FIG. 21A , the root canal  1612  of the tooth  1600  by using a manual instrument selected from the 1 st  category, 2 nd  class, No. 8 with an approximate 2% taper, in increasing order to No. 15 with an approximate 2% taper, in order to reach the shoulder  1610 . For the purpose of illustration only,  FIG. 16A  shows an enlarged view of a cutting tip  1633 A, while  FIG. 16C  shows an enlarged view of a non-cutting tip  1633 B. 
         [0220]    The endodontist then, at step  2120 , further enlarges the root canal  1612  using electrically rotating instruments selected from the 2 nd  category, starting with files No. 10 and an approximate 2% taper, in an increasing order to No. 20 with an approximate 2% taper, up to the shoulder  1610 . 
         [0221]    The endodontist continues to enlarge the root canal  1612  at step  2120 , using electrically rotating instruments selected from the 3 rd  category, starting with files No. 20 to 25 with an approximate 4% taper, and continuing with files No. 25 with an approximate 6% taper, whenever possible, until the shoulder  1610  is reached. Preferred results were obtained with a No. 20 instrument with an approximate 4% taper. 
         [0222]    Once the portion of the root canal  1612  up to the shoulder  1610  has been widened to the desired dimensioned, the endodontist continues at step  2130  by creating a path  1655  through the shoulder  1610  using manual NiTi instruments  1620  selected from the 1 st  category, 1 st  class, No. 20 with an approximate 4% taper and a cutting tip  1633 , by exerting a manual force in a push and pull motion along the arrow F. Thereafter, the instrument  1620  is withdrawn. The relatively large cross sectional surface of the cutting tip  1633 A avoids opening a false canal when exerting a relatively high manual force. 
         [0223]    At step  2140 , the endodontist enlarges the path  1655  using a manual NiTi instrument selected from the 1 st  category, 1 st  class, No. 20 having an approximate 4% taper and a non-cutting tip  1633 B in order to preserve the opened path  1655 . 
         [0224]    In case of difficulty in enlarging the path  1655 , the endodontist uses a manual stainless steel instrument selected from the 1 st  category, 1 st  class, No. 20 having an approximate 2% taper with a cutting tip to penetrate the shoulder  1610  in a push and pull motion. Thereafter, it is recommended to manually enlarge the newly opened path  1655  using a manual stainless steel instrument selected from the 1 st  category, 1 st  class, No. 20 having an approximate 2% taper with a non-cutting tip  1633 B. 
         [0225]    Still at step  2140 , the endodontist continues to enlarge the path  1655  using a manual NiTi instrument selected from the 1 st  category, 1 st  class, No. 20 having an approximate 4% taper and a cutting tip  1633 . A manual NiTi instrument selected from the 1 st  category, 1 st  class, No. 20 and an approximate 4% taper with a non-cutting tip  1633 B, may be used in order to preserve the newly opened path  1655 . 
         [0226]    In case of difficulty in penetrating the shoulder  1610 , the endodontist uses a manual stainless steel instrument  1620  selected from the 1 st  category, 1 st  class, No. 15 having an approximate 2% taper and a cutting tip  1633 , in order to penetrate the shoulder  1610 . This step is followed by the use of a manual stainless steel instrument  1620  selected from the 1 st  category, 1 st  class, No. 15 having an approximate 2% taper with a non-cutting tip  1633 B, in order to preserve the newly opened path  1655 . In case the abovementioned instruments  1620  fail to open the required path  1655 , the endodontist may use smaller stainless steel instruments  1620  in the same sequence until reaching the apex  1650 . 
         [0227]    Still at step  2140 , the endodontist further enlarges the opened path  1655  manually until the introduction of stainless steel instruments selected from the 1 st  category, 1 st  class, No. 20 with an approximate 2% taper (alternatively NiTi instrument No. 20 with an approximate 4% taper) having a cutting tip  1633 A and then a non-cutting tip  1633 B, is made possible. 
         [0228]    As further illustrated in  FIG. 16C , once the path  1655  has been enlarged to the desired dimensions, the endodontist then uses, at step  2150 , electrically operated NiTi instruments  1630  selected from the 1 st  category, 1 st  class, 2 nd  category, with a non-cutting tip  1633 B, followed by the use of a non-cutting tip instrument  1630  of the 3 rd  category. In performing this step  2150 , the endodontist sequentially uses, in increasing order, the instruments  1630  starting with instruments selected from the 1 st  category, 1 st  class, No. 10 to No. 20 with an approximate 2% taper, and then instruments from No. 20 to No. 25 of the 2 nd  category and finally instrument No. 20 or 25 with an approximate 4% taper of the 3 rd  category at the apex  1650 . 
         [0229]    As illustrated at step  2160  and also in  FIG. 14E , upon completion of step  2140  as described earlier, the endodontist clears the widened root canal of any debris, as is known in the field, in preparation for the final obturation step. 
         [0230]    As illustrated at step  2170  and also in  FIG. 14F , the endodontist obturates the root canal with the appropriate filling material  1446 , as is known in the field. 
         [0231]    According to the another embodiment of the present invention, it is possible to directly reach the apex  1650 , following step  2140 , by using electrically operated instruments selected from the 1 st  category, 1 st  class, provided with non-cutting tips, in an increasing order from files No. 10 with an approximate 2% taper to files No. 20 with an approximate 4% taper, followed by instruments of the 2 nd  and 3 rd  categories as deemed appropriate by the endodontist. 
         [0232]    According to yet another embodiment of the present invention, in less difficult cases, after enlarging the path  1655  by a manual NiTi instrument No. 20 (1 st  category, 1 st  class) having an approximate 4% taper and a non-cutting tip (e.g.,  1633  B) the endodontist, may be able to directly reach the apex  1650  by using electrically operated non-cutting tip NiTi instruments, starting by enlarging the path  1655  with a file No. 20 having an approximate 4% taper (1 st  category, 1 st  class) then using in increasing order, non-cutting tip instruments selected from the 1 st  category, 1 st  class, from No. 10 to No. 20 having an approximate 2% taper and then No. 20 with an approximate 4% taper (1 st  category, 1 st  class), and finally using instruments Nos. 20 to 25 having an approximate 2% taper of the 2 nd  category followed by instruments No. 20 or 25 having a 4% taper of the 3 rd  category. 
         [0233]    It is worth noting that the root canal is irrigated with sodium hypochloride and EDTA (Ethylenediaminetetraacetic acid) at each relevant step of process  2100 . 
         [0234]    The following X-Rays ( FIGS. 25 and 37 ) provide supporting illustrations of this novel process  2100 : 
         [0235]      FIG. 25A  shows a hypercalcification, a shoulder, and a broken file in the mesial canals of tooth no. 36.  FIG. 25B  shows the broken file.  FIG. 25C  shows the bypassing of the broken file, the penetration of the shoulder and the piercing of the hypercalcification in the 2 nd  mesial canal and reaching the apex with the new instrument, according to the present invention.  FIG. 25D  shows the fully hermetic obturation of the treated root canal. 
         [0236]      FIG. 37A  shows a blockage in the mesial canal of tooth no. 16 due to a shoulder.  FIG. 37B  shows the elimination of the shoulder with the new instrument reaching the apex, according to the present invention. 
         [0237]    VI—Method of Penetrating Root Obstructions Resulting from a Previous Root Canal Treatment 
         [0238]    With reference to  FIG. 17 , it comprises  FIGS. 17A and 17B  and illustrates an exemplary tooth  1700  having a root canal  1712  that is blocked or obstructed by, for example a residual, hardened paste  1710  from a previous root canal treatment. With further reference to  FIGS. 22A and 22B , the treatment method  2200  is performed according to the following steps: 
         [0239]    As further illustrated in  FIG. 17A , the endodontist opens the root canal  1712  at step  2210  of  FIG. 22A  using instruments  1720  selected from the 1 st  category, 2 nd  class, starting with file No. 10 with an approximate taper 2%, in order to create an initial path  1733  in the existing residual paste  1710 , using an instrument  1725  with a cutting tip, to a depth of approximately 2 mm to 3 mm, using an appropriate softening agent. 
         [0240]    At step  2220 , the endodontist enlarges the opened initial path  1733  with instruments  1720  selected from the 2 nd  and 3 rd  categories. 
         [0241]    At step  2230 , the endodontist pierces again the residual paste  1710 , through the initial path  1733 , using an instrument  1720  selected from the 1 st  category, 2 nd  class, file No. 15, to an additional depth of approximately 2 mm-3 mm. 
         [0242]    At step  2240 , the endodontist enlarges the width of the initial path  1733  using instruments  1720  selected from the 2 nd  and 3 rd  categories. 
         [0243]    With further reference to  FIG. 17C , and to step  2250  of  FIG. 22B , the endodontist pierces again the widened initial path  1733  using an instrument  1730  selected from the 1 st  category, 2 nd  class, file No. 15, with a possible recourse to file No. 10 of the 1 st  category, 2 nd  class, until the apex  1750  is reached. 
         [0244]    At step  2260 , the endodontist enlarges the opened path  1755  with instruments selected from the 2 nd  and 3 rd  categories in preparation for the obturation step. 
         [0245]    In the event an unexpected obstruction is faced inside the resistant paste, the aforementioned steps of process  2200  will be used depending on the nature of the encountered obstruction, i.e. fractured instrument, hypercalcification, curved root canal or shoulder. 
         [0246]    It should be clear that if the obstruction within the root canal includes a resistant, residual paste  1710 , the process  2000  described earlier in connection with  FIG. 20  relating to the piercing of the hypercalcification, can be used, in the same sequence from step  2030  through step  2070 . 
         [0247]    As illustrated at step  2270  and also in  FIG. 14E , upon completion of step  2260  as described earlier, the endodontist clears the widened root canal of any debris, as is known in the field, in preparation for the final obturation step. 
         [0248]    As illustrated at step  2280  and also in  FIG. 14F , the endodontist obturates the root canal with the appropriate filling material  1446 , as is known in the field. 
         [0249]    It is worth noting that the root canal is irrigated with sodium hypochloride and EDTA (Ethylenediaminetetraacetic acid) at each relevant step of process  1900 . 
         [0250]    The following X-Rays ( FIGS. 27, 33, 37, 38 ) provide supporting illustrations of this novel process  2200 : 
         [0251]      FIG. 27A  shows three broken files with resistant paste in tooth no. 35 blocking the totality of the root canal.  FIG. 27B  shows the bypassing of the three broken files and the piercing of the resistant paste with the new instrument reaching the apex, according to the present invention.  FIG. 27C  shows the fully hermetic obturation of the root canal. 
         [0252]      FIG. 33A  shows an incomplete root treatment of tooth no. 35 due to hypercalcification blocking the third apical of the root canal.  FIGS. 33B, 33C , and  33 D show the piercing of the old resistant paste and progressively piercing the hypercalcification with the new instrument reaching the apex, according to the present invention. 
         [0253]      FIG. 37A  shows a blockage in the mesial canal of tooth no. 16 due to a shoulder and a resistant paste.  FIG. 37B  shows the elimination of the shoulder and the piercing of the resistant paste with the new instrument reaching the apex, according to the present invention. 
         [0254]      FIG. 38A  shows a false canal and a resistant paste in tooth no. 37.  FIG. 38B  shows the avoidance of the false canal and the piercing of the resistant paste with the new instrument reaching the apex, according to the present invention. 
         [0255]    It is to be understood that the specific embodiments of the invention that have been described are merely illustrative of certain application of the principle of the present invention. Numerous modifications may be made to the present instruments and methods described herein without departing from the spirit and scope of the present invention.