Endodontic treatment system

Abstract

An endodontic system of shaping instruments, irrigation cannulas, filling instruments and materials designed to safely create specific tapers of root canal preparations and to clean, dry, seal, and restore them. The shaping instruments are a series of reamers, files, and handpiece burs, made of stainless steel, nickel-titanium, or other alloys, which impart several different specifically-tapered apertures in root canals. The instruments have one or more safety features to eliminate perforating curved roots, including shorter flute length as the angle of taper increases and variable sharpness along the length of the flute portion, as well as variable flute pitch along the length of the flute portion to maximize cutting efficiency and resistance to breakage, and a rounded tip to eliminate ledging. The hand instruments have a handle designed to optimize use of the instruments in apically directed, notary cutting motions. The irrigation cannulas, the condensation heat carriers, pluggers, injection needles, and backfillers, and the materials, including drying paper points, filling materials, and restorative post systems, have shapes which match the canal tapers created by the shaping instruments.

Description

shank tip to flute pitch at the tip shank (the overall flute pitch ratio) is four in the FIG. 4 embodiment. The flute pitch ratio, defined as the flute pitch at any point along the working portion of the file relative to the flute pitch at the tip, diminishes linearly along the length of the working portion of the file. Thus, in the embodiments of FIGS. 4A-4E the flute pitch ratio diminishes linearly from four one at the shank tip to one 0.25 at the tip shank. Other ratios may be selected for other file sets, if desired, but a linear decrease in flute pitch ratio from shank tip to tip shank is preferred.

Similarly, the sharpness of the cutting flutes may be decreased from shank to tip, decreasing the chances of a cutting flute near the tip catching in a canal wall which easily causes file breakage when the file is used in a rotary cutting motion. The result is increased cutting efficacy near the shank end flutes where more dentin removal is needed and where the file has its greatest diameter and strength. This variable dulling may be accomplished by a number of means, including an increasing “U” blade as taught in the Arpaio, Jr., et al U.S. Pat. No. 4,934,934 (see FIG. 4C), a progressive flute edge radius as seen in FIG. 4D, or a different flute rake angle as seen in FIG. 4E.

FIG. 4F shows an enlarged view of the file tip. The file tapers to a blunt or radiused tip 64. As the slightly-smaller blunt tip blends into the cutting flutes of the file, the non-cutting tip transitions into lands 65, and finally into fully-sharp flutes 60. The blunt tip prevents apical ledging and the transitional lands prevent transportation of the apical canal path during shaping procedures. These are important features when using a single file to create the full canal shape, as the aggressive more-coronal dentinal cutting decreases the clinician's tactile awareness of file tip function. As described below, file tip diameters may be consistent between sizes of file tapers, or may vary between file taper sizes.

FIG. 4G shows the files in FIGS. 4 and 4F with cutting flutes 57 spiralling in reverse direction to aid the use of apically-directed counter-rotary filing. As most dentists use their handpieces in the clockwise direction and are used to filing in a clockwise direction, the reverse flute direction shown in this embodiment allows clinicians to rotate their handpiece files or hand files in the clockwise direction they are used to and still gain the advantages of apically-directed counter-rotary filing motions.

FIG. 4H shows the files 50 in FIGS. 4 and 4G mounted in a latch-grip slow-speed handpiece attachment 81, although these files may be effectively powered by mechanical, sonic or ultrasonic handpieces with any type of handpiece attachment including various finger handles 22 and 52 in FIGS. 1A and 4, respectively, which may be accepted by specifically designed endodontic handpieces.

Views A and B of FIG. 5 are schematic views illustrating a set of two standard ISO-tapered files 20, each equipped with a handle 52 in accordance with the present invention. With the advent of the Balanced Force cutting motion for root canal instruments, clinicians are no longer pulling files out of canals to cut dentin. Using this counter-clockwise cutting motion the files are only directed into the canal during dentinal cutting, making the standard hour-glass handles which are commonly used less effective. Unlike the present invention, the standard handles 22 are too narrow to gain much leverage in rotary cutting motions, and most bothersome is the discomfort experienced after holding them tightly for an hour or so in a tough case. Pushing apically on a standard handle 22 is like squeezing a BB shot between one's fingers, which can be decidedly uncomfortable. The handle 52 (FIGS. 4 and 5) is wide enough to afford easy rotation and is comfortable to hold when applying strong apical forces to shaping files.

FIG. 6A is a schematic view illustrating the potential for the gouging of curved canal walls with a terminal shank-end flute 62. As was called out in FIG. 4, the non-fluted shank 54 of these files is slightly smaller than the terminal shank-end flute, to provide chip space and prevent binding around canal curvatures. This proved to gouge the outside of canal curvatures in prototype testing; therefore it was concluded that some functional design element was needed to support the terminal flute 62 as it traverses severe canal curvatures. FIGS. 6B and 6C, corresponding to FIGS. 4A and 4B, respectively, represent two alternative variations in design which eliminate gouging and maintain smooth continuous canal preparations. FIG. 6B shows a transitional land 66 between the terminal flutes and the smaller shank 54 of the file. FIG. 6C shows a guide ring 68 positioned on the shank 54 of the file at a distance 69 from the terminal flute 62 to support the terminal flutes as they cut around canal curvatures.

FIGS. 7A and 7B show two series of files 50 which are identical in taper for corresponding files in the two figures, except that the extent of the taper of the flutes in the working portion 56 and the lengths of the working portion are different. As is apparent in FIGS. 7A and 7B, the tapers of the flutes in the working portion 56 of the files 50A and 50E shown are less than the tapers shown in files 50D and 50H. In FIG. 7B, the working portion 56 in file 50H is shorter than that in file 50E, thereby limiting the diameter of the largest shank-end cutting flutes, an improvement over the files seen in FIG. 7A without the variable flute lengths.

As may be seen from a comparison of FIGS. 8A and 8B, it has been determined through clinical practice and research that, although different root canal morphologies may require different apical tapers in their final preparation shape, the great majority of canals only need a certain amount of enlargement in the coronal part of the root canal. Creating a single rate of taper through the full length of the root canal is not only unnecessarily difficult, but it needlessly weakens root structure and risks perforation through over-enlargement of curved roots as seen in FIG. 8A.

FIG. 9, views A-C, shows a non-ISO-tapered file series 90 having the same tapers but different maximal diameters 92, 94, and 96. These variations are useful when treating roots of different widths, files 90A and 90B being appropriate, respectively, for narrow roots and roots of average width (FIG. 10A), and file 90C addressing a wide-rooted tooth (FIG. 10B). Additionally this file set may be used sequentially in the same root, as seen in FIGS. 11A-11C, to sequentially enlarge the canal.

FIG. 12 shows a variably-tapered Hedstrom file series 100, each with SAFE EDGE™ 102 as disclosed in my prior U.S. Pat. No. 4,836,780, but with the additional safety feature comprising shorter flute lengths 104 as the tapers increase. This is an important modification for the reasons discussed in connection with FIGS. 8A and 8B.

FIG. 13 shows an ISO-tapered file series 110 with flute lengths becoming progressively shorter as the tip diameters become greater.

FIG. 14 shows a set of variably-tapered files 120 which have the same or nearly the same tip diameters with tapers which increase proportionally by 100% from each file to the next. For example, file 120A has a taper of 0.05 (mm/mm); file 120B has a taper of 0.1 mm, file 120C has a taper of 0.2 mm, and file 120D has a taper of 0.4 mm. This allows a short range of tapers to address a large variation in root canal morphologies.

FIG. 15 shows a set of files 130 with a single non-ISO taper with flute lengths becoming progressively shorter as the tip diameters become proportionally greater. In this example, the tips increase 100% from one file to the next, file 130A having a tip diameter of 0.15 mm, file 130B having a tip diameter of 0.3 mm, file 130C having a diameter of 0.6 mm and file 130D having a tip diameter of 1.2 mm. This allows a smaller set of instruments to address a wide range of variation in canal morphology without weakening the root by overshaping.

FIG. 15A shows a single “U” blade file of a set of “U” blade files like that shown in FIG. 15, the files all having the same non-ISO taper. The tips vary in diameter by proportional increments as described in the Schilder U.S. Pat. No. 5,017,138.

FIG. 15B, views A through E, shows a set of negotiation files 140 which are given the designation numbers 07/01, 10/02, 12/03, 15/04 and 17/05. The first number corresponds to tip diameter which increases from 0.075 mm for file 140A to 0.175 mm for file 140B in increments of 0.025 mm. Each of the files has a flute length of 16 mm. The maximum flute diameter increases proportionally from 0.235 mm for file 140A to 0.975 mm for file 140E. Tapers increase in 0.01 mm/mm increments from file 140A with a taper of 0.01 mm/mm to file 140E with a taper of 0.05 mm/mm.

This assortment of increasing tip diameters and tapers with increasing file size allows a 0.15 mm file maximal stiffness which is needed when attempting to find and enter an occluded calcified canal prior to shifting to a 0.075 mm file which provides the maximum tactile response when negotiating the often tortuous terminal aspect of a canal after coronal enlargement with the larger file. The intended procedure with the negotiating files 140 in the set of FIG. 15B is to begin with a larger file which is suited to initial penetration and then shift to smaller files which are suited to work into the apical region after the initial opening is cleared.

Views A through E of FIG. 16 schematically represent a file 150 which is pre-shaped in accordance with an aspect of my invention. The files 150 are manufactured of a nickel-titanium alloy called Nitinol™. This alloy is a metal with a “memory” which has the capability of retaining a given shape, once established. After the files are fabricated from Nitinol™, the tips are shaped to the preferred degree of curvature in an implement 152 and are held in that shape during an annealing step. This develops the “memory” of the curve near the end or throughout the length of the file. The file 150 is superflexible for the first two-thirds of its length while the hook at the end makes it easier to direct the file down into the apical region of the root canal, particularly where the root is rather tortuously curved or twisted. These files 150 are to be provided in sets according to the variable tapers disclosed herein with respect to ISO-tapered files like that shown in FIG. 1A or sets of non-ISO-tapered files having similar tapers as shown in FIGS. 13, 15 and 15A and the corresponding descriptions thereof. The sets of files 150 may also have varying degrees of curvature between sets or from one file to the next in a set. Thus, there will be a set of files 150 having a first pre-set curvature, another set of files 150 having a different pre-set curvature and additional sets of pre-shaped desired corresponding to any desired curvature or shape.

View F of FIG. 16 shows a file 151 having dulled cutting edges 153 along one side of the file. The file 151 is constructed of Nitinol™ and pre-curved as are the files in views A through E of FIG. 16 but the curve imparted into the memory of the file during the fabrication process extends throughout its fluted portion. This configuration of a SAFE EDGE™ file of my prior patent insures that the non-cutting side of the flutes automatically follows the inner side of the curved root, thereby further protecting against perforation.

Turning now to FIG. 17, views 17C through 17I schematically represent different types of implements which are to be used with correspondingly shaped files, such as the files 50 in views A and B, in systems in accordance with the present invention in the preparation and filling of a root canal. (Note that the flutes of file 50 in view B are formed in a counterclockwise direction, opposite to the file in view A.) Each of these implements is designed to be provided in a set, corresponding to the sets of files of varying tapers as described hereinabove.

View 17C of FIG. 17 represents an irrigating cannula 200 comprising a shaft 202 mounted in a head 204. The cannula 200 has a hollow bore 206. The shaft 202 is tapered, beginning at the point 208, and terminating in a fine tip 210. The tapered shape aids in displacement of fluids throughout the length of the canal, providing a more effective way to freshen the irrigation fluids at the end of the canal than irrigation cannulas currently available. Transverse opening 212 communicates with the hollow bore 206 to permit irrigating fluid to be directed into the apical region of the root canal to remove debris developed by using a set of files such as 50 (FIGS. 4 and 5). A set of variable taper cannulas is provided to match the variable taper files such as 50.

View 17D of FIG. 17 represents a paper point 220 which is used to dry a root canal. The paper point 220 is shaped similarly to the files, as described hereinabove, and has a corresponding taper beginning at the point 222 and terminating at a fine tip 224. A set of paper points 220 is provided to match the variable taper files such as 50 (FIGS. 4 and 5).

Commercially available paper points are invariably white. I have discovered, however, certain beneficial results from using colored paper points, preferably in a pastel shade which possesses the property of changing color when moistened. While paper points do not noticeably change color when wet. However, a colored paper point possesses the capability of displaying the length of the root canal in those instances were the root canal is kept patent to its terminus, in which case the paper point can be inserted beyond the terminus to be moistened by jaw tissues apical to the tooth. There is also a telltale indication if the canal is not completely dried. Good results have been obtained with salmon-colored, aqua-colored, beige-colored and green pastel-colored paper points which exhibit a definitely noticeable change of color when moistened. Thus, the paper point 220 may be considered to be colored in one of the shades in the group of green pastel-colored, salmon-colored, aqua-colored and beige-colored in preferred embodiments of the invention. For convenience in selecting corresponding files, the handles of the files may be provided with corresponding colors.

View 17E of FIG. 17 represents a gutta percha point 230 having a taper corresponding to the files described hereinabove beginning at a point 232 and terminating at a fine point 234. After the paper point 220 is used to dry the interior of the root canal, a gutta percha point such as 230 is pushed into the apical region and packed tightly to fill the apical region of the root canal. It is important to note that the shank end is not tapered, reflecting the maximum flute diameters of corresponding files shown in FIG. 17A.

View 17G of FIG. 17 represents a gutta percha obturating carrier 240 with gutta percha filling material 246 installed thereon. The carrier 240 tapers in the manner previously described, beginning at the corresponding point 242 and continuing to its termination at the tip 244. Conventional obturating carriers are smoothly tapered from shank to tip. A set of such carriers may be provided to match the shapes described hereinabove for the sets of files 50. However, in a variant of this embodiment, I propose an obturating carrier provided with flutes along its tapered portion, essentially like the flutes 60 on the file 50 in view 17A except for the direction of the spiral. It will be understood that view 17H may be taken to schematically represent such a fluted region between the point 242 and the tip 244. Along this fluted region, the flutes are in a counterclockwise spiral, viewed from the proximal end of the carrier 240′. This obturating carrier has similar shapes as the files in views A and B and it may be used alongside a previously fit gutta percha cone, to thermoplastisize the gutta percha, or the carrier may be coated with pre-heating alpha and/or beta phases gutta percha and carried into the canal. By running the carrier handpiece, the carrier backs out of this canal, leaving canals filled with the material.

Finally, view 17I of FIG. 17 represents a restorative post 250, tapered as described beginning at the point 252 and continuing to its termination 254. The end 254 is not as finely pointed as is shown for the cannula 200, paper point 220 and gutta percha point 230 because its tapered length is shorter than those other implements. The restorative post 250 is designed to be anchored in the root canal at a position short of the terminal end of the canal.

FIG. 18A is a schematic view of a heat carrier/plugger tool 260 modified in accordance with my invention. This tool is shown installed in a handpiece 262 (in broken outline) having a chuck 264 (also in broken outline) for tightening the root 260 in the handpiece 262.

The heat carrier/plugger 260 has a gooseneck bend near the point A leading to a straight section terminating in an extended tapered tip 266. A condensing portion 265 is made of stainless steel with a hollow core through which a conductor (not shown) extends for providing connection to an electrical circuit. When the circuit is energized, the stainless steel heater 265, being of relatively high resistance material, develops heat at the very end for softening the gutta percha material with which it is used.

When used in the practice of my method in filling a root canal with gutta percha material in a single compression wave, existing heat carrier/pluggers have a tendency to bend in the mid portion. I provide a thin stainless steel support member 268 which is welded or soldered to the tool 260 along the back thereof between the points A and B, along line 270. The shape of the support member 268 in the region between points B and C conforms closely to the shape of the nose of the chuck 264 of the handpiece 262 but is not affixed thereto. This permits the chuck 264 to be rotated during tightening and loosening of the shank of the tool 260 while limiting the extent that the tool can give during use, since the slightest bend brings the adjacent surface of the support member 268C into contact with the nose of the chuck 264 and prevents any further bending.

FIG. 18B shows two versions of the heat carrier/plugger tool 260 of FIG. 18A associated with respectively corresponding gutta percha cones. In the pair designated A, the gutta percha cone has the traditional taper of presently used gutta percha cones. The heat carrier/plugger 260A is provided with a taper which corresponds to these traditional tapers, thereby enabling the tool to be inserted into or near the apical region of the root in a single wave of condensation. In the pair designated B in FIG. 18B, the gutta percha point is like the point 230 in view E of FIG. 17 with a taper beginning at point 232 and extending to the fine tip 234. The tapered portion 266 of the heat carrier/plugger 260B begins at a point 267 and corresponds to the tapered portion of the gutta percha point 230. Use of the heat carrier/plugger 260 in the canal filling method of my invention is represented schematically in FIG. 19.

In FIG. 19, the heat carrier/plugger 260 is tapered to correspond to the shape of the canal which has been formed prior to the filing step. The taper may correspond to that of tool 260A for use with conventional tapered gutta percha cones prepared by using other shaping files or it may have the taper of the terminal portion 266 of the tool 260B, corresponding to the taper in the terminal portion of the gutta percha point 230 (see FIG. 18B). As indicated in FIG. 19, view A, the gutta percha point is fully inserted into the root canal. The distal end of the heat carrier/plugger 260 is inserted into the canal cervical region and energized to soften and permit the heated tip element 265 to move through the gutta percha material within the canal. As the tool 260 moves further into the root canal, it develops hydraulic pressure which forces the softened gutta percha material and sealer cement into the lateral branch portions of the canal, represented at 274. Finally, as shown in view C, the heat carrier/plugger 260 is withdrawn, leaving the lateral branches 274 and the apical portion of the root canal filled and sealed with the obturation materials.

FIG. 20 (views A through D) shows a tapered heat carrier/plugging tool 300 as it is used to soften and downpack through a pre-fit gutta percha cone 246 in a continuous wave of condensation. FIG. 20A shows the electric heat carrier/plugger 302 withdrawn into its condensation sheath 304 in preparation for heating and compacting gutta percha into the canal. FIG. 20B shows the first move into the canal with the heat carrier on high heat level, with the tool searing into the gutta percha cone until the compaction sheath binds the canal near its orifice level, thus creating the secondary seal necessary for a closed system within which to exert optimally controlled hydraulic compaction forces on the heat-softened gutta percha and the less viscous sealer against the canal walls. FIG. 20C shows the second move into the canal as the heat carrier/plugger 302 is extended out of the compaction sheath 304, heating and plastically deforming the gutta percha and sealer into all dimensions of the root canal system. FIG. 20D shows the withdrawal of the tool 300 from the canal after the extended heat carrier/plugger 302 bottoms out near the apical terminus of the canal, with the soft sticky surplus gutta percha and sealer removed from the canal on the tool. The canal is shown ready for restorative post placement of the type specified in FIG. 17, or for backfilling with the tool and material shown in FIG. 21.

FIG. 21 shows another electric heat carrier of a configuration to afford fast ideal backfilling of canals which have been downpacked but not posted. FIG. 21A shows a preformed gutta percha plug 230 with the shape of the empty coronal part of the canal and a groove or hole 231 to allow introduction of the narrow electric heat carrier of FIG. 21B. FIG. 21B shows a tool 320 whereby a narrow, parallel heat carrier 322 extends through the end of a hollow or notched plugger 324. FIG. 21C shows a gutta percha plug 230 mounted on the backfilling tool 320, and that set of tool and materials placed in the empty coronal part of the canal with sealer 326. FIG. 21D shows that same tool/material set after heat has been created by the heat carrier 322, softening the end of the gutta percha plug 230. As the heat carrier tip 322 is withdrawn coronally, the plugger 324 is pushed apically, thereby condensing the gutta percha 230 from its tip to its butt end. FIG. 21E shows the termination of backfilling as the heat carrier tip 322 is fully retracted into the plugger 324, resulting in a dense obturation of the softened gutta percha.

Although there have been described hereinabove various specific arrangements of an endodontic treatment system in accordance with the invention for the purpose of illustrating the manner in which the invention may be used to advantage, it will be appreciated that the invention is not limited thereto. Accordingly, any and all modifications, variations or equivalent arrangements which may occur to those skilled in the art should be considered to be within the scope of the invention as defined in the annexed claims.

Claims

1. A set of endodontic files for use in preparing root canals in teeth wherein the files vary in taper, one from another, each file comprising:

a shank;

a tip; and

a flute portion which extends between the tip and the shank;

wherein each of said files having a greater taper than another one of the files in said set has a shorter flute portion than said other file.

2. The set of files of claim 1 wherein the shank of each file has a proximal end, remote from said flute portion, which is embedded in a pear-shaped handle comprising a scored tapered section having an enhanced gripping area to facilitate applying torque to the file in combination with apically directed force.

3. The set of files of claim 1 wherein the shanks of said files in the set are all of the same diameter.

4. The set of files of claim 1 wherein in each file the diameter of the largest flute in said flute portion is greater than the shank diameter and wherein the file includes a transition portion extending from the largest diameter flute to the shank, said transition portion including a pair of lands diminishing in diameter from the largest diameter flute to the shank.

5. The set of files of claim 4 wherein said shank has a diameter equal to approximately 95% of the diameter of the largest flute.

6. The set of files of claim 4 further including a shank guide which is spaced along the shank from the largest diameter flute by a distance which allows a chip space for tooth dust to collect during filing procedures.

7. The set of files of claim 1 wherein the tip of each file is smoothly rounded and devoid of cutting edges.

8. The set of files of claim 7 wherein the tip has a diameter which is slightly smaller than the diameter of the smallest diameter flute.

9. The set of files of claim 8 further including a second transition section between the tip and the flute portion which includes a pair of lands continuing from the smallest diameter flute to the tip.

10. The set of files of claim 1 wherein the flute portion of each file includes a plurality of flutes, each provided with cutting edges about the periphery of the file, said cutting edges diminishing in diameter and increasing in pitch and sharpness with distance from the largest diameter flute.

11. The set of files of claim 1 wherein each file of said set comprises a Hedstrom-type file with the cutting edges dulled along one side of the file and wherein the lengths of the flute portions vary inversely with the degree of file taper.

12. The set of files of claim 1 wherein each file of said set comprises a K-type file with the cutting edges dulled along one side of the file and wherein the lengths of the flute portions vary inversely with the degree of file taper.

13. The set of files of claim 1 wherein each file of said set comprises a Hedstrom-type file with the cutting edges dulled along one side of the file and wherein the lengths of the flute portions vary inversely with the diameter of the file tip.

14. The set of files of claim 1 wherein each file of said set has a preselected curve in a region of the flute portion near the tip which is set in the file during fabrication.

15. The set of files of claim 14 wherein each file of said set is fabricated of a nickel-titanium alloy.

16. The set of files of claim 15 wherein said alloy is Nitinol™.

17. A set of endodontic files for use in preparing root canals in teeth wherein the files vary in taper, one from another, each file comprising:

a shank varying in diameter from every other file in said set;

a tip varying in diameter from every other file in said set; and

a flute portion which extends between the tip and the shank, the flute portions of all files in said set being the same length;

wherein each of said files having a greater taper than another one of the files in said set has a larger diameter tip and a larger diameter shank than said other file.

18. The set of files of claim 17 wherein the taper varies from 0.01 mm/mm for the smallest diameter file to 0.05 mm/mm for the largest diameter file in said set.

19. The set of files of claim 18 wherein the variation in taper from file to file is 0.01 mm/mm.

20. The set of files of claim 17 wherein the variation in shack diameter from file to file is 0.185 mm.

21. The set of files of claim 17 wherein the length of the flute portion of each file of said set is 16 mm.

22. The set of files of files of claim 17 wherein the variation in tip diameter from file to file is 0.025 mm.

23. The set of files of claim 17 wherein a first file of said set has a tip diameter of 0.075 mm, a shank diameter of 0.235 mm, and a taper of 0.01 mm/mm.

24. The set of files of claim 17 wherein a second file of said set has a tip diameter of 0.1 mm and a shank diameter of 0.420 mm, and a taper of 0.02 mm/mm.

25. The set of files of claim 17 wherein a third file of said set has a tip diameter of 0.125 mm, a shank diameter of 0.605 mm, and a taper of 0.03 mm/mm.

26. The set of files of claim 17 wherein a fourth file of said set has a tip diameter of 0.15 mm, a shank diameter of 0.790 mm, and a taper of 0.04 mm/mm.

27. The set of files of claim 17 wherein a fifth file of said set has a tip diameter of 0.175 mm, a shank diameter of 0.975 mm, and a taper of 0.05 mm/mm.

28. The set of files of claim 17 wherein the shank of each file has a proximal end, remote from said flute portion, which is embedded in a handle configured to facilitate manipulation of the associated file.

29. The set of files of claim 28 wherein each file handle is pear-shaped and configured to provide an enhanced gripping area to facilitate the application of torque to the file in combination with apically directed force.

30. The set of files of claim 29 wherein the handle of each file is shaped with planar proximal and distal ends oriented transversely to the longitudinal axis of the file.

31. The set of files of claim 30 wherein the handle of each file comprises a smooth curved surface portion extending from the distal end to a maximum diameter and a scored section tapering from the plane of maximum diameter to said proximal end of said handle.

32. The set of files of claim 31 wherein the scored section of each file handle comprises 70% to 85% of the length of the handle.

33. The set of files of claim 32 wherein the scored section of each handle is 80% of the length of the handle.

34. The set of files of claim 33 wherein the handle of each file is 10 mm in overall length and the length of the scored section is 8 mm.

35. The set of files of claim 31 wherein the scored section of each file handle comprises a plurality of longitudinally directed grooves oriented side-by-side about the periphery of the handle, each of said grooves tapering slightly in width from the plane of maximum diameter to the proximal end of the handle.

36. The set of files of claim 35 wherein each of said grooves comprises a pair of beveled sides intersecting at the bottom of the groove.

37. The set of files of claim 1 wherein the flute portion of each file includes a plurality of flutes, each provided with cutting edges about the periphery of the file, said cutting edges diminishing in diameter and sharpness and increasing in pitch with distance from the largest diameter flute.