IMPROVED ENDODONTIC OBTURATOR

Abstract: This invention is an obturator for use in filling an endodontically prepared root canal in a tooth formed as an elongated body having a handle portion (10) and a shaft (12), the handle portion (10) being configured for grasping by a practitioner whereby the shaft (12) may be inserted into a root canal, the shaft tapering from the handle (10) to the shaft distal end (14), the shaft having an exterior surface having a generally linear groove (22) therein extending from near the handle to the shaft distal end, or at least adjacent the shaft distal end, the groove providing a channel for flow of excess filler material as the shaft is positioned into a prepared root canal, increased flexibility of the shaft, and a passageway that will accept a slender, tapered metallic retrieval tool, such as a typical endodontic file, to assist in the removal of the shaft from a root canal.

Description: IMPROVED ENDODONTIC OBTURATOR BACKGROUND OF THE INVENTION Until about 1987, the most common technique for filing an endodontically prepared root canal of a tooth was with a filler material (usually gutta percha) applied by means of an instrument called a "condenser" that included a small diameter, usual straight portion with a blunt end that was inserted into a root canal. Small quantities of gutta percha or other filler material were repeatedly carried into the canal by the condenser having surfaces that when manipulated exerted a compacting force to urge the gutta percha to fill the root canal. This procedure was time consuming and often did not result in adequately filling a root canal of an endodontically prepared tooth. U.S. Patent 4,758,156, issued in 1988, disclosed a tool for applying filler material to an endodontically prepared root canal, the tool including an obturating shaft or carrier portion to which gutta percha was coated and adhered. The tool, after heating the gutta percha coating, was then inserted into the root canal with apical force with the gutta percha being hydraulically placed throughout the canal. The handle portion was then rotated or manipulated until the shaft separated at a predetermined point, with the handle portion then being removed. U.S. Patent 4,894,011, issued in 1990, disclosed further improvements to this basic concept, including in Figures 7 and 13 thereof, forming spiral grooves on the exterior surface of the obturator for the purpose of augmenting retention of filler material and increasing flexibility of the shaft. By rotating the obturator in one direction the filler material is compacted, while reversing direction helped removal of the obturator from the filled root canal. U.S. Patent 5,118,297, issued June 2, 1992, disclosed even further important advancements in endodontic obturators. This patent provides an endodontic obturator formed of plastic and including gutta percha or other filler material being formed on the obturator such that it could be heated, by a flame of a burner or in an oven, to assist in conveying filler material into a root canal. The patents discussed herein above, that is, U.S. Patents 4,758,156; 4,894,011 and 5,118,297 are each incorporated by reference as fully as if the text and drawings were repeated herein. SUMMARY OF THE INVENTION An improved obturator for use in filling an endodontically prepared root canal is disclosed. The improved obturator includes an elongated slender body having a proximal end and a distal end. The body has a handle portion at the proximal end, the handle portion being in the form of an enlarged diameter portion of configuration and dimension to be manipulated by the thumb and forefinger of a practitioner for use in filling a root canal . Extending from the handle portion is a shaft dimensioned to be received in an endodontically prepared root canal, the shaft preferably being tapered and having a surface adapted to receive filler material thereon. Formed in the shaft portion is one or more grooves that extend from adjacent the handle portion to adjacent the distal end of the shaft. In one embodiment the groove can extend all the way to the distal end of the shaft while in another embodiment the groove extends to immediately adjacent the distal end so that the distal end has an uninterrupted cicrcumferential surface in a plane drawn perpendicular to the longitudinal axis of the shaft. This rounded terminal surface that may be termed "a bullet nose" end configuration. The groove formed in the external surface of the shaft serves at least three important functions. First, the groove permits a passageway for the flow of excess filler material upwardly out of the depths of a root canal during the obturation process. That is, any excess filler material can freely move out of the root canal thereby making it easier for the practitioner to insert the distal portion all the way to the root canal apex. A second advantage of the provision of one or more grooves in the exterior surface of the obturator shaft is that flexibility of the shaft is increased. Root canals are seldom straight requiring the obturator to bend and flex as it is inserted into a root canal during the obturation process, the increased flexibility imparted by the provision of one or more grooves improves the performance of the obturator. A third and significant advantage obtained by the provision of one or more grooves in the exterior surface of the shaft of the obturator is that a re-entry area is provided. For example, an instrument, such as a file, particularly one having a barbed exterior surface, can be inserted into a root canal following the groove formed in the obturator shaft, providing means whereby the obturator can be extracted from the root canal . One of the serious problems with the use of obturators is that they interfere with reopening the root canal in the event an infection develops or for other reasons it is important to have access to a root canal after it has been obturated. In the past, extracting obturators has been a serious problem. However, with the provision of this invention, the obturator body can be effectively extracted. The extraction capability afforded by this invention is particularly important when it is fully appreciated that a file or other slender metallic extraction instruments inserted into a root canal following the groove formed in the obturator body can extend to substantially the full length of the shaft to engage the shaft along its full length and permit it to be extracted. It is easily seen that if an extractor engages only a portion of the shaft, extraction can frequently result in severing the shaft, leaving the lowermost portion that is adjacent the tooth apical area in the tooth. Putting it another way, the most difficult part of the obtuator body to extract is the most distal portion which is the portion having the smallest cross- sectional area and therefore the area easiest to sever during an extraction process. By this invention, an extraction tool can be inserted to substantially the full depth of the root canal along the groove provided in the shaft to substantially increase the possibility that the full length of the shaft can be removed from a root canal . In one embodiment of the invention the obturator includes filler material formed on the shaft portion so as to expedite filling a root canal. A better and more complete understanding of the invention will be obtained from the following description of the preferred embodiments taken in conjunction with the attached drawings . BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an elevational enlarged view of an endodontic obturator of this invention. Figure 2 is a greatly enlarged cross-sectional view as taken along the line 2-2 of Figure 1 showing one configuration of a groove formed in the external surface of the shaft portion of an obturator. Figure 3 is an enlarged end view taken along the line 3-3 of Figure 1. Figure 4 is a cross-sectional view as shown in Figure 2 but showing an alternate design of the groove formed in the external surface of the shaft portion of the obturator body. Figure 5 is a view as shown in Figure 3 but showing the appearance of an obturator body as seen from the distal end when a groove having straight sidewalls as shown in Figure 4 is employed. Figure 6 is an elevation view of the obturator body of Figure 1, but including filler material adhered to the shaft portion. Figure 7 is an enlarged cross-sectional view taken along the line 7-7 of Figure 6 showing the obturator body in cross-section having a groove with an arcuate cross- sectional configuration and showing filler material as formed on the obturator shaft portion. Figure 8 is a fragmentary elevational view of the distal end portion of an obturator body shaft portion showing a groove formed in the external surface of the shaft portion, wherein the groove terminates just short of the shaft distal end leaving a "bullet nose" end configuration . Figure 9 is an elevational view of the obturator shaft distal end portion taken along the line 9-9 of Figure 8. Figure 10 is an elevational cross-sectional view of a typical bicuspid tooth showing a root canal having therein a shaft portion of an endodontic obturator of this invention severed from the handle portion during the procedure for filing the root canal and showing the use of a retrieval tool (typically an endodontic file) that is inserted into the root canal along the groove formed in the exterior surface of the obturator to assist in removing the severed shaft portion from the root canal. Figure 11 is a cross-sectional view taken along the line 11-11 of Figure 10. DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings and first to Figure 1, an enlarged elevational view of an embodiment of the improved endodontic obturator is shown. The obturator includes a proximal handle portion 10 dimensioned to be manipulated between the thumb and forefinger of the user. Integrally extending from handle portion 10 is a shaft portion 12 that terminates in a distal end 14. Shaft 12 is tapered and has an external surface adapted to receive an endodontic filler material, such as gutta percha, thereon. Shaft portion 12 tapers from the maximum diameter at junction 16 where the shaft meets a conical portion 18 of handle 10, the shaft tapering from a maximum diameter at junction 16 to a minimum diameter at distal end 14. Junction 16 is an external indication only of change in the shape of the tapered surface of shaft 12 and handle conical portion 18 and does not indicate a separation in the overall integral obturator. Integrally formed on shaft 18 are spaced apart length indicators 20 that are, as explained in U.S. Patent 5,118,297, useful for indicating the distance that the shaft proximal end 14 has penetrated into a root canal so that the practitioner can, after the canal is filled with the filler material, insert the obturator and know that the distal end has penetrated to the depth as indicated by an indicator 20. Handle portion 18 has depth indicators that are useful when the obturator is employed in a tooth having an unusually long root canal. The obturator described to this point is substantially identical to the obturator described in previously issued U.S. Patents 4,894,011 and 5,118,297. A significant and important improvement is the provision of a groove 22 formed in the external surface of the obturator shaft portion 12. The groove 22 extends from an upper portion of the shaft 12 to the distal end 14. In the embodiment of Figure 1 the groove extends completely to the end of the shaft portion 14. Figure 8 and 9 show details of the distal end portion 14 of the shaft 12 including a groove 22A portion formed in the external surface of the shaft portion, having a groove terminal point 24 terminating short of the shaft distal end 14A. This embodiment, alternative to the groove 22 extending through distal end 14 of Figure 1, permits end 14A to be defined by an uninterrupted circumferential surface providing a "bullet nose" end configuration. The bullet nose end 14A has an important advantage over the end configuration of Figure 1. By providing a full, uninterrupted circumferential surface, the bullet nose end configuration is less likely to engage or "hang up" on an irregularity in a root canal that would interfere with the complete advancement of the obturator to the root apex. Further, the terminus of a root canal at the apex of a tooth provides a potential point of entry of contaminants into the tooth. By employing an obturator having a circumferential end as seen in Figures 8 and 9, the obturator can be more effectively close the apex end of the root canal and thereby more effectively guard against entry of contaminants into the canal after the endodontic procedure has been completed. Figure 2 shows a cross-section of the obturator shaft 12 and groove 20. In this embodiment, the groove 22 is arcuate. However, the cross-sectional shape of the groove can vary. Figure 4 is an example of an alternate embodiment, wherein groove 22B has an angular cross- sectional configuration. The angle forming the walls of the groove can vary considerably from an acute to an obtuse angle. Not only can the cross-sectional shape of groove 22 vary but the depth can vary considerably. One important advantage of providing groove 22 in the shaft portion of the obturator is that it increases flexibility of the shaft. However, the groove has the contravailing characteristics of reducing the strength of the shaft. Therefore, the depth, shape and cross-sectional area of groove 22 must be selected as a compromise between preserving the required strength of the shaft and achieving the desired increase in flexibility of the shaft . In addition to increased flexibility of the shaft portion, another significant advantage of groove 22 is that it allows for escape of excess filler material as the obturator is inserted into a root canal having filler material therein. An important function of the obturator is to compact filler material in a root canal to eliminate, as much as possible, any voids and to cause the filler material to flow into lateral fissures that frequently characterize root canals. Therefore, it is important that the root canal be as full as possible of filler material as the obturator is inserted into the canal but, at the same time, it is important that provision be made for the escape of excess material. When the obturator is inserted into a root canal having filler material therein, the obturator should be positioned at its full depth into the canal, with distal end 14 as close as practically possible to the root canal apex. Therefore, any excess accumulation of filler material in the root canal can, by hydraulic action, interfere with positioning the obturator in the root canal in a tooth in some instances. With the provision of groove 22 any excess filler material can flow to the tooth surface and hydraulic resistance to positioning the obturator shaft portion in the root canal is alleviated. Figure 3 is an end view of the obtuator showing the groove 22 extending to distal end 14. Figure 5 shows an end view of an obturator having an angular groove 22B as shown in Figure 4. An important advancement of the state of endodontics has been the commercial availability of obturators having filler material formed thereon. Figures 6 and 7 show the obturator of Figure 1 having filler material 26 formed thereon. Filler material 26 is typically gutta percha but may be other compounds that have desirable characteristics for functioning as a root canal filler. The typical commercially available obturator has filler material 26 formed thereon by the manufacturer which at ambient temperature is relatively rigid. Before the obturator having the filler material thereon is inserted into a root canal, the filler material 26 can be heated, either over an open flame or in an oven, to a temperature at which it become semi-molten to more readily flow into root canal spaces. Figure 6 shows an elastomeric washer 28 that can be used for assistance in compacting a filler material into a root canal, as has been explained in the previously issued patents referred to hereinabove. In addition, a highly important advantage of the groove 22 is that it provides a re-entry passageway into a root canal. If an endodontic procedure is unsuccessful, that is, if infection or other problems develop, it is sometimes desirable that further work be done within the root canal. For this reason it is important to be able to extract an obturator from a root canal. Heretofore, this has been a serious problem. If obturators are made of plastic, the preferred material of which the present invention is made, the obturator can be drilled out of the root canal. However, drilling is not easily accomplished in a root canal that is not straight. Therefore, it is highly desirable to be able to extract an obturator from a tooth. The groove 22 provides a passageway by which a practitioner can insert a dental file or other long, thin metal instrument having an irregular surface, particularly one having a barbed surface, to engage the plastic obturator and permit extraction of the obturator. Since the groove 22 extends the full length of the obturator shaft, the file or other similar tool having the characteristics of being thin, flexible and strong, and with a surface that will adhere to plastic obturator shaft 12, can be inserted the full length of the obturator, thereby permitting the full obturator shaft to be extracted from a tooth. Whereas the upper portion of an obturator, being a larger diameter portion of the tapered shaft, can usually be grasped in some way and removed, a common problem with conventional obturators is breaking off the obturator so that the lower portion remains in the root canal. By the provision of the groove 22 an instrument can be extended to the apical end 14 of the obturator yet permitting its extraction, if necessary. Figures 10 and 11 illustrate this important aspect of the improved obturator. A tooth 30 is shown in cross- section, the tooth being representative of a bicuspid with a coronal area 32 and root apexes 34 and 36. The tooth has a first root canal 38 and a second root canal 40. The first root canal 38 is shown as having been endodontically treated, that is, enlarged, shaped and cleaned by the use of dental files whereas the second root canal 40 is more typical of the appearance of the root canal prior to being endodontically treated. The tooth has a pulp cavity 42 that, after the enamel and dentine which normally covers the pulp cavity at the coronal area 32 has been removed, exposes root canals 38 and 40. Positioned in root canal 38 is a shaft 12 of an endodontic obturator, such as the obturator of Figure 1, the shaft having been inserted into root canal 30 in conjunction with filler material 44, such as gutta percha. Shaft 12 has been severed at 46 as is the procedure for the use of the obturator for filling a root canal. The tooth 30 is shown as the tooth would appear with the first root canal 38 filled by the obturator and showing the circumstances under which, for one reason or another, the obtuator shaft needs to be extracted from the root canal . As has been previously stated, since the obturator shaft portion is preferably formed of plastic, it can be drilled out of the root canal 38 but such procedure is difficult because root canals are seldom straight and are usually of tapered shape. Therefore, it is highly desirable to be able to extract obturator shaft 12. For this purpose, an extraction tool, generally indicated by numeral 48 is employed. The extraction tool 48 has a metal shaft 50- and a handle portion 52, the handle being typically formed of plastic. Shaft 50 has an exterior surface that is irregular and may include barbs, grooves or the like. The extraction tool 48 could conveniently be an endodontic file that is used by practitioners to endodontically prepare a root canal. Figures 10 and 11 show the shaft 50 of the extraction tool 48 inserted into the root canal using the access provided by groove 22 that is formed in obturator shaft 12. The irregular surface of shaft 50 tends to embed into the plastic obturator shaft 12 so that upon outward pull relative to the tooth coronal area 32, using handle 52, the obturator shaft 12 can be extracted. The provision of groove 22 in the shaft portion of the obturator allows an extraction tool or endodontic file to be inserted substantially to the full length of the shaft as compared with an attempt to insert an endodontic file along a shaft that has no groove. Without the provision of groove 22 it is difficult to extend the shat of an extraction tool to substantially the full length of an obturator shaft 12. However, with the provision of the groove 22 the possibility of extending the extraction tool shaft to substantially the distal end of the filler shaft is substantially improved, thereby improving the possibility of successfully extracting the full length of an obturator shaft from a root canal. In the embodiment of Figure 8 and 9, wherein the groove 22A terminates a short space away from the obturator distal end, nevertheless, the groove extends substantially to the complete end of the obturator so as to permit its full extraction. The obturator groove 22 should preferably be linear or at least substantially linear. The groove 22 may be slightly helical and still meet the three important purposes enumerated herein. That is, the groove 22 could curve for a fraction of a circumference around the external peripheral surface of obturator shaft 12. However, a groove that spirals more than about 180° around the shaft periphery along the length of the shaft is not desirable since it makes insertion of a file or other tool used for removal of the obturator more difficult and would likely interfere with the function of allowing escape of excess filler material. The claims and the specification describe the invention presented and the terms that are employed in the claims draw their meaning from the use of such terms in the specification. The same terms employed in the prior art may be broader in meaning that specifically employed herein. Whenever there is a question between the broader definition of such terms used in the prior art and the more specific use of the terms herein, the more specific meaning is meant. While the invention has been described with a certain degree of particularity, it is manifest that many changes may be made in the details of construction and the arrangement of components without departing from the spirit and scope of this disclosure. It is understood that the invention is not limited to the embodiments set forth herein for purposes of exemplification, but is to be limited only by the scope of the attached claim or claims, including the full range of equivalency to which each element thereof is entitled.

Claims: WHAT IS CLAIMED IS: 1. An obturator for use in filling an endodontically prepared root canal in a tooth, comprising: an elongated body having a proximal handle portion and a distal shaft portion, whereby the shaft portion may be inserted in a root canal, the shaft portion tapering from said handle portion to a distal end, the shaft portion having an exterior surface having a generally linear groove therein extending from adjacent said handle portion to adjacent said distal end. 2. An improved obturator according to claim 1 wherein said groove is dimensioned to permit any excess liquid filler material within a root canal to flow by way of said groove from within the exterior of a root canal. 3. An endodontic obturator according to claim 1 wherein said shaft distal end is rounded to form a bullet nose and wherein said groove extends to adjacent but not through said bullet nose whereby said bullet nose is left at least substantially intact. 4. An endodontic obturator according to claim 1 wherein said groove is, in transverse cross-section, of generally V-shaped configuration. 5. An endodontic obturator according to claim 1 wherein said groove is, in transverse cross-section, of general arcuate configuration. 6. An endodontic obturator according to claim 1 wherein said shaft portion has filler material formed thereon encompassing at least a substantial portion of said shaft and said groove. 7. An endodontic obturator according to claim 1 wherein said groove is configured and dimensioned to receive a slender, tapered retrieval tool to augment removal of the shaft portion from a root canal. 8. An endodontic obturator according to claim 7 wherein said groove is configured and dimensioned to receive an endodontic file for assistance in removing the shaft portion from a root canal . 9. An improved obturator according to claim 1 wherein said shaft portion exterior surface is generally circular in transverse cross-section. 10. An improved obturator according to claim 1 wherein at least said shaft portion is formed of plastic. 11. An improved obturator according to claim 1 wherein said body handle portion and said portion are integral and formed of plastic.

Inventors: JOHNSON WILLIAM B, JOHNSON, WILLIAM, B.
Applicants: JOHNSON WILLIAM B, TULSA DENTAL PRODUCTS INC, JOHNSON, WILLIAM, B., TULSA DENTAL PRODUCTS INC.
Application year: 1998
Main classification: A61G5
IPC codes: A61C5, A61C13