ENDODONTIC APPARATUS FOR RETROFILL CAVITY PREPARATION

Abstract: An endodontic tool has a working tip including a cylindrical (22) segment terminating in a conical end (20). A shoulder (25) is provided at the end of the cylindrical segment which is spaced from the conical end. The conical end and the cylindrical segment each have a surface for removing tooth material when the tool is vibrated at sonic frequencies. A stem connects to the second cylindrical segment (24) at a right angle and is connectable to a conventional sonic hand piece so that vibratory energy generated within the hand piece is transmitted to the working tip by way of the stem. The hand piece provides vibratory motion generally along its longitudinal axis, and the stem is received in the hand piece with the stem axis at an angle to the longitudinal axis of the hand piece. The stem can be rotated about its own axis in the hand piece such that orientation of the working tip relative to the longitudinal axis of the hand piece is readily and releasably adjustable.

Description: ENDODONTIC APPARATUS FOR RETROFILL CAVITY PREPARATION This invention relates generally to dental apparatus for use in endodontic procedures and more particularly to a tool and hand piece suitable for retrofill cavity preparation, that is, preparation of a root cavity for filling from the bottom, by access through an opening provided in the jawbone. In root canal surgery, the space containing the pulp is opened by drilling into the tooth from the top. The pulp is the removed and a suitable material is used to fill the entire internal volume of the tooth. However, if pain persists or if problems develop subsequently to cause the patient to feel pain in the tooth, it may be necessary to drill into the bottom of the tooth root which is seated in the jawbone. The tip or bottom of the root is removed and the bottom of the root canal 1 o is bored out and is subsequently filled with a filler material. In the past, such bore has been made by an vibratory instrument operating at ultrasonic frequencies. Vibrations are induced in the tool by a mechanism, typically including a piezoelectric element, in a hand piece to which the tool is mounted, and which is adapted to be held by the dental surgeon. Rotary drilling bits are also sometimes used in place of, or in conjuction with, ! 5 tolls operating with vibratory motion. Because of the various locations in the mouth where root canal surgery may be required and because of the relative inaccessibility of many of these areas and the small space between cheek and jawbone, tolls of many different shapes have been constructed to accommodate the various tooth locations so that the bottom of the root can be reached for retrofill cavity preparation 0 regardless of the tooth's location. No single tool is known which is sufficiently versatile to operate at all of the tooth locations. Many possibilities of misaligning a drilled cavity, are present. Such hazards are especially prevalent when using devices that vibrate at ultrasonic frequencies, since a small deviation from an intended path of preparation can quickly and undesirably remove relatively large quantities of tooth material. Among others, the risk of an unintended breaking 25 through of the side wall of a tooth is increased at ultrasonic frequencies. At best, operation of these tools involves very delicate and time consuming procedures. Further, when operating at ultrasonic speeds with conventional tools, it is difficult to avoid enlarging the entrance to the cavity drilled at the bottom of the root such that the cavity becomes conical in shape, that is, increasing in diameter toward the bottom of the root. Such a 30 conical shape, when filled form the bottom of the tooth is preferred, since the friction form the parallel side wall of the bore aids in maintaining the filler material in place. In the prior art, U.S. Patent N° 5,094,617 issued march 10, 1992, provides an ultrasonic tool having a conical working end that is connected at an angle to an elongated stem. Stems of SUBSTITUTE SHEET many different shapes, both amoothly curved and also bent at clearly defined angles, are disclosed. Regardless of shape, the stem is received coasially in a compatible tool holder of a hand piece for a dental retrofill instrument. Longitudinal ultrasonic vibrations generated in the hand piece are transmitted to the stem and to the conical working end of the tool, which is applied to a patient's tooth. The above-mentioned hazards associated with ultrasonic tools affect usage of the tools of the type disclosed in Patent '617. The need for numerous tools, each of a different shape so as to access teeth of different locations can be an inconvenience to the surgeon. SUMMARY OF THE INVENTION It is an object of the invention to provide an improved endodontic tool for retrofill cavity preparation that operates in a conventional sonic hand piece using conventional air and water inputs currently available at modern dental offices. Another object of the invention is to provide an improved endodontic tool for retrofill cavity preparation, that is small in size and capable of adjustable installation in a hand piece so as to enable a single tool to be used at a multitude of different tooth locations. A further object of the invention is to provide an improved endodontic tool for retrofill cavity preparation that reduces the hazards of unintentional removal of tooth material associated with ultrasonic tools. Still another object of the invention is to provide an improved endodontic toll for retrofill cavity preparation which is an efficient tooth material removing device and will enlarge the lower portion of the root canal in generally cylindrical shaps. Yet another object of the invention is to provide an improved endodontic tool for retrofill cavity preparation that is not only versatile but is simple to manufacture and economical to produce. An endodontic tool in accordance with the invention has a working tip including a cylindrical segment terminating in a tapered tip. A shoulder is provided at the end of the cylindrical segment spaced from the tapered tip. The shoulder limits or gives indication of the depth of drilling into the tooth root. The tapered tip and the cylindrical segment connected thereto both have surfaces that are suitable for removing tooth material when the tool is vibrated at sonic frequency and placed into contact with a tooth surface. A stem connects at one end to the shoulder at a substantially right angle with respect to the lengthwise extension of the working tip. The stem is connectable at its other end to a conventional sonic hand piece of, for example, the type used for cleaning teeth, so that vibratory energy generated within the hand piece is transmitted to the tool, that is, to the working tip, by way of SUBSTITUTE SHEET the stem. The hand piece provides vibratory motion generally along its longitudinal axis, and the stem is received in the hand piece with the axis at an angle to the longitudinal axis of the hand piece. The stem can be rotated, about its own axis, in the hand piece such, that orientation of the working tip relative to the longitudinal axis in the hand piece is readily and releasibly adjustable. The shoulder provided on the working tip gives an indication to the surgeon of the extent of tool entry into the root cavity when drilling. Operation at sonic frequencies, as compared to ultrasonic, makes the tool much easier and safer to use. Accordingly, the risk of unintended removal of tooth material, beak-through at the side walls of the tooth, and unintended enlargement at the entrance to the drilled cavity, is substantially reduced. Because the tool operates at lower vibrational frequency, when, deviations from an intended path do occur, the risk of unintended removal of tooth material is substantiall less than when operating with ultrasonic devices. The tool in accordance with the invention is simple in shape and construction and, accordingly, is inexpensive to produce. It can operate on conventional sonic equipment using standard air and water connections available at the site of all modern dental chairs ; no special accessories or tool holders are required to drive the tool. Further objects and advantages of the invention will be apparent from the following detailed description and drawings. The invention accordingly comprises the features of construction, combination of elements, and arrangement of parts which will be exemplified in the constructions hereinafter set forth, and the scope of the invention will be indicated in the claims. BRIEF DESCRIPTION OF THE DRAWING For a fuller understanding of the invention, reference is had in the following description to presently preferred embodiments, taken in connection with the acccompanying drawings, in which : Figure 1 is a front elevational view of an endodontic tool in accordance with the invention, Figure 2 is a side elevational view of the tool of figure 1, Figure 3 illustrates the tool of figures 1,2 mounted for use in a hand piece, and Figure 4 is a side elevational view of an alternative embodiment of an endodontic tool in accordance with the invention. SUBSTITUTE SHEET DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to the figures, a tool 10 includes a working tip 12 that is connected to a stem 14 of extended length. The axis 16 of the working tip 12 intersects the axis 18 of the stem 14 at an angle of approximately 90°. The working tip 12 includes a conical end 20 connected to a first cylindrical segment 22, which, in turn, is connected to a second cylindrical segment 24 of larger radius, whereby a shoulder 25 is formed. The conical end 20, and cylindrical segments 22,24 are centered on the tip axis 16. The stem 14 includes a shaft 26 that is joined to the end of the working tip 12 via a curved intermediate portion 28 so as to avoid injuries to the patient as the tool is maneuvered in use in the oral cavity. A resilient sleeve 30 covers a lower portion 32 of the shaft 26. The lower stem portion 32 is used in engaging the working end, or tool holder, 34 of a hand piece 42 (fig. 3), as discussed hereinafter. The tool holder 34 is conventional, that is, presently available on the market, although a special tool holder may be constructed for use with the tool 10 of the present invention. For example, the tool 10 may be used in an MM1500 hand piece (Sonic Air MM1500 Endo System), marketed by Micro-Mega, Woodside, New York. This is a device intended for use at sonic frequencies. However, it should be understood that the working tip 12 in accordance with the invention is not limited for use with any particular tool holder. The tip 12 can be connected to any stem 14 that is particularly constructed for connection to other commercially available tool holders that are capable of providing proper vibratory motions in desired magnitudes and directions. II is only necessary that the lower portion 32 of the stem 14 be constructed, with or without the sleeve 30, to cooperate with the fastening means of the particular tool holder. The stem 14, with the resilient sleeve 30, has performed satisfactorily with the tool holder by Micro-Mega, mentioned above. The axis 18 of the stem is positioned transversely to the longitudinal axis 36 of the tool holder 34 when the tool 10 is mounted to the tool holder. The two axes, 16,18 of the working tip 12 and stem 14 are coplanar. Thus, the tool 10 can be rotated about the stem axis 18 to any orientation relative o the longitudinal axis 36 of the tool holder 34 before the tool 10 is tightened into position. The tool 10 is therefore readily positionable for convenient operation on any tooth in the mouth. SUBSTITUTE SHEET The tool holder of figure 3 also includes a nozzle 38 to provide coolant water for the tool 10 if required, and a guard 40 that encircles the stem 14 of the tool 10. These elements are not novel portions of the invention and accordingly are not discussed in detail herein. Figure 3 illustrates the tool 10 mounted with the working tip 12 lying in a common plane with the axes 18,36, with the conical end 20 pointing back, in the general direction of the hand piece 42, where the assembly is gripped by the surgeon when using the device. As noted above, the tool 10 can be rotated about the stem axis 18, as indicated by the arrow 44, before the tool 10 is locked into position on the tool holder 34 for use. Thus, the conical end 20 can be pointed downward (Fig. 3) or at any angle relative to the axis 18, and lie in or out of the plane of figure 3. The tool 10 is made of any material having biological compatibility and sufficient strength for use in endodontic work, for example, stainless steel. The external surfaces of the working tip 12 need not be specially formed in manufacture in order ot abrade tooth material. It is sufficient that the surface of the working tip 12 is not polished. For example, a useful tool can be turned form stainless steel on a lathe and the bent to shape, without polishing. Diamond coated and barbed surfaces may also be use. Vibratory forces provided along the longitudinal axis 36 of a tool holder and acting transversely to the axis 18 of the stem have provided suitable energy to the working tip 12 of such a tool in clinical testing for the purposes described herein, irrespective of the angular position of the axis 16 of the tip 12 with respect to the axis 36. In tools 10 that have performed satisfactorily the length of the conical end 20 (from the apex 48 to the base 50 of the cone) is in a range of approximately 0.5 to 2.0 millimeters. The length of the first cylindrical segment 22 is in a range of approximately 1.5 to 3 millimeters. The length 54 of the second cylindrical segment 22 is in a range of approximately 0.1 to 0.5 millimeters and the radius of the second cylindrical segment 24 is in a range of approximately 0.3 to 0.8 millimeters. The shaft 26 has approximately the same radius of the resilient sleeve 30 is in a range of approximately 0.8 millimeters to 1.2 millimeters. The angle 56 between the working tip axis 16 and the stem axis 18 is in a range of approximately 90° plus or minus 10°. Tests of the tool 10 were performed using conventional sonic hand pieces, as indicated above, to confirm that the energy levels produced by such conventional sonic instruments, which energy levels are lower than those of comparable ultrasonic instruments, were not only sufficient for cavity preparation with the tool tip of the instant invention but further, allowed such preparation with less risk to the patient, easier handling for the dental surgeon and better long terme adhesion of the filling material. The tool assembly including the tool 10 and hand piece 42 operated with conventional inputs of air and water. It was possible to obtain a deep preparation, which followed the original path of the apical root canal. Because of the small size of the tool 10, SUBSTITUTE SHEET it was found in clinical tests that the tooth apices were easily accessible to the MM 1500 hand piece, and removal of peri-apical bone was either not necessary or could be kept at a minimum. The shoulder 25, produced by the different diameters of the first and second cylindrical segments 22,24 of the working tip 12, prevented working to excessive depth in the tooth. The straight cylindrical contour of the first cylindrical segment 22 allowed the formation of a cylindrical rather than a conical cavity in the bottom of the tooth root. This provides increased friction and thus better retention of the filler material which is inserted from the bottom of the tooth cavity. The conical end 20 was highly effective for positioning and in leading the tool into the cavity and in removal of filler material that remained from earlier endodontic procedures. Because of the lower energy levels in the sonic device and because of the small size and adjustability of the tool 10, a fine, well-formed, cylindrical, cavity preparation can be made without removal of an excessive amount of tooth of material. Many changes may be made in the above constructions without departing from the spirit or the scope of the invention. For example, whereas a conical end has been described in the embodiment above and illustrated in figures 1-3, other pointed and tapered ends may be incorporated with good effect. As above, both the pointed or tapered end and the first cylindrical segment have external working surfaces that are suitable for removing tooth material when the tool is vibrated at sonic frequency and placed into contact with a tooth surface. Any tapering end surface that aids in accurately positioning the tool in the apical opening at the initiation of tooth material removal, and that includes a working surfaces, is entended to fall within the scope of the invention. Figure 4 illustrates an alternative embodiment of an endodontic tool 10' in accordance with the invention. The tool 10' of fig. 4 is substantially similar to the tool 10 for figs. 1 and 2. Accordingly, similar parts are given the same reference numerals in figs. 1,2 and 4. The end 60 of the working tip 61 is conical and both the conical end 60 and the cylindrical segment 62 are covered with barbs 64 that enhance the drilling capability of the tool. Either or both surfaces may incorporate the barbs, and the respective surfaces may be partially or completely barbed. A shoulder 25 is provided at the intersection of the barbed surface with the cylindrical segment 24. In other respects, the embodiment of figure 4 is similar to that in figures 1 and 2 and may be attached to a tool holder handpiece as illustrated in figure 3. The second cylindrical segment 24, illustrated in both of the embodiments may have another cross section, that is, not a circular cross section. However, a shoulder 25 is produced at the intersection between the working cylindrical portion 22,62, with or without barbs 64, and the intermediate portion 24 between the cylindrical segment 22,62 and the shaft 26. SUBSTITUTE SHEET Further, in order to provide greater rigidity to the working tip 12,61 of the tool, and to reduce the space wherein the tool 10,10' can be used, it is desirable that the length 54 of the intermediate portion 24 be made as short as possible, as may be dictated by the particular manufacturing techniques that are used in producing the tool. Thus, the first cylindrical segment 22,62 may abut directly against the shaft 26 in alternative embodiments in accordance with the invention. In this manner the stem 14 serves as a depth indicator and controller. Additionally, an indication of depth of tool penetration into a tooth can be provided to the dental surgeon by a construction other than the shoulder 25 that is illustrated in the figures. Any radical projection at the desired distance from the end 48 can be provided. Thus, in an alternative embodiment in accordance with the invention, the working cylindrical segment 22,62 can have the same diameter as the intermediate cylindrical segment 24. A small radial flange (not shown), can be provided at a location corresponding to the position of the shoulder 25 in the illustrated embodiments. This radial extension or flange need not extend for 360° about the axis 16 and need not be of uniform radial extension about its entire periphery. Essentially, a stop means is provided at a particular location on the tool to aid the surgeon in ascertaining and controlling the depth of penetration by the working surfaces of the device. Depending upon the methods used in fabricating the tool, stop means can be formed in many shapes. In a construction, in accordance with the invention, wherein length of the segment 24 is reduced, or is eliminated (zero length), the shaft 26, as stated above, may serve the function of a stop in controlling drilling depth. Reduction in the length 54 minimizes the required working space and enhances the usefulness of the tool. Because there are many different depth and diameter requirements for the opening in a tooth, which is operated upon, a range of sizes in the endodontic tools is desirable, as has been described above with references to figures 1 and 2. Effective performance has been achieved with barbed tools 10' wherein the outer diameter 66 of the barbed surface, inclusive of the barbs, is in a range of approximately 0.20 millimeters to 0.50 millimeters, and the diameter 68 of the cylindrical segment 62, (exclusive of the height of the barbs), is in the range of approximately 0.17 milimeters to 0.47 millimeters. The distance between the pointed end 48 and the shoulder 25 or stop means may be in a range of approximately 1 millimeter to 4 millimeters. When the working segment 22,62 is cylindrical and the intermediate portion 24 is also cylindrical, the shoulder 25 is continuous around the periphery of the tool. When the intermediate portion 24 is not round, the shoulder 25 may have a varying width (radial extension) around the circumference of the cylinder 22,62 and may not be continuous. A construction wherein both the working segment and the intermediate portion 24 are cylindrical, is preferred. SUBSTITUTE SHEET A stem length 70 in a range of approximately 5 millimeters to 15 millimeters has provided satisfactory performance with a shaft 26 having a diameter in a range of approximately 0.4 to 1.0 millimeters. It will thus be seen that the objects set forth above, and those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in the above constructions without departing from the spirit or the scope of the invention, it is intended that all matter contained in the above description, or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. For instance, the hand piece could be replaced by a vibratory hand piece. SUBSTITUTE SHEET

Claims: WHAT IS CLAIMED IS 1 . An endodontic apparatus for retrofill cavity preparation, comprising : a tool including a working tip having a first axis, said tip including a pointed end connected to one end of a first cylindrical segment, said first cylindrical segment and said pointed end being aligned to said first axis, the outer surfaces of both said pointed end and said first cylindrical segment being working surfaces for acting on a tooth and for removing tooth material, stop means positioned proximate the other end of said first cylindrical surface, said stop means extending radially of said first axis and beyond the working surface of said first cylindrical segment ; and a stem for connection to a tool holder and having a first end and a second end, said second end being connected to said first cylindrical segment proximate said stop means and said other en of said first cylindrical segment, said stem being selectively positionable about a second axis when said stem is connected to said tool holder. 2. An endodontic apparatus as in claim 1, wherein said pointed end is conical. 3. An endodontic apparatus as in claim 1 , further comprising a second segment connected to the other end of said first cylindrical segment, the cross section of said second segment being larger than the cross section of said first cylindrical segment, said stop means including a shoulder formed at the connection between said first cylindrical segment and said second segment by their respectively different cross sections. 4. An endodontic apparatus as in claim 3, wherein said second segment is cylindrical. 5. An endodontic apparatus as in claim 2, further comprising a second segment connected to the other end of said first cylindrical segment, the cross section of said second segment being larger than the cross section of said first cylindrical segment, said stop means including a shoulder formed at the connection between said first cylindrical segment and said second segment by their respectively different cross sections. 6. An endodontic apparatus as in claim 5, wherein said second segment is cylindrical. 7. An endodontic apparatus as in claim 1 , segment and said second segment by their respectively different cross sections. 6. An endodontic apparatus as in claim 5, wherein said second segment is cylindrical. 7. An endodontic apparatus as in claim 1 , wherein the working surface of at least one of said pointed end and said first cylindrical segment is barbed. 8. An endodontic apparatus as in claim 2, wherein the working surface of at least one of said pointed end and said first cylindrical segment is barbed. SUBSTITUTE SHEET 9. An endodontic apparatus as in claim 5, wherein the working surface of at least one of said pointed end and said first cylindrical segment is barbed. 10. An endodontic apparatus as in claim 1, further comprising a tool holder having length and connection means for releasibly gripping said stem, said tool holder including dynamic means for providing vibrations at least along a lengthwise third axis, said vibrations being transmitted to said working tip via said stem when said stem is gripped by said connection means, said second axis and said third axis intersecting at a first angle. 11. An endodontic apparatus as in claim 10, wherein said first and second axes meet at a second angle. 12. An endodontic apparatus as in claim 11, wherein said connection means, when released, permit rotation of said stem about said second axis, whereby the orientation of said working tip relative to said tool holder is adjustable. 13. An endodontic apparatus as in claim 1, wherein said first and second axes meet at an angle. 14. An endodontic apparatus as in claim 1, wherein said first axis and said second axis intersect at substantially a right angle. 15. An endodontic apparatus as in claim 10, wherein said dynamic means provides vibrations at frequencies in the sonic range. 16. An endodontic apparatus as in claim 2, wherein said conical and has a length from the apex to the base of said end in a range of approximately 0.5 to 2.0 millimeters and said base has a radius in a range of approximately 0.1 to 0.5 millimeters. 17. An endodontic apparatus as in claim 2, wherein said first cylindrical segment has a length in a range of approximately 1.5 to 3.0 millimeters and a radius in a range of approximately 0.3 to 0.8 millimeters. 18. An endodontic apparatus as in claim 6, wherein said second cylindrical segment has a length in a range of approximately 0.0 to 3.0 millimeters and a radius in a range of approximately 0.3 to 0.8 millimeters. 19. An endodontic apparatus as in claim 1, wherein in the length of said stem is in a range of approximately 20 to 30 millimeters and the radius of said stem is in a range of approximately 0.8 to 1.2 millimeters. 20. An endodontic apparatus as in claim 1, further comprising a resilient sleeve, and wherein said stem is round and has a radius in a range of approximately 0.3 to 0.8 millimeters and is encircled with said resilient sleeve at one end, said sleeve having an outer radius in a range of approximately 0.8 to 1.2 millimeters. 21. An endodontic apparatus for retrofill cavity preparation, comprising : SUBSTITUTE SHEET a working tip having a first axis, said tip including a generally pointed end connected to one end of a cylindrical segment, said cylindrical segment and said pointed end being aligned to said first axis, the outer surface of said pointed end and the outer surface of said cylindrical segment being working surfaces for acting on a tooth and for removing tooth material ; a stem having a first end and a second end, said second end being connected to said cylindrical segment at the end of said cylindrical segment away form said pointed end, a second axis extending between said first and second ends of said stem, said first and second axes meeting at an angle of approximately 90° ; and an elongated hand piece having connection means for releasibly gripping said stem, said hand piece including dynamic means for providing sonic vibrations at least along a third axis lengthwise of said hand piece, said sonic vibrations being transmitted to said working tip via said stem when said stem is gripped by said connection means, said second axis and said third axis intersecting at an angle. 22. An endodontic apparatus as in claim 2, wherein the axial length of said conical end is in the range of appromately 15 percent to 65 pecent of the distance from an apex of said conical end to said stop means. 23. An endodontic apparatus as in claim 2, wherein said conical end has a length from the apex to the base of said conical end in a range of approximately 0.5 to 2.0 millimeters and said first cylindrical segment has a length in a range of approximately 1.5 to 3.0 millimeters. 24. An endodontic apparatus for retrofill cavity preparation, comprising : a working tip having axis, said tip including a tapered end connected to one of a cylindrical segment, said cylindrical segment and said tapered end being aligned to said first axis, the outer surface of said tapered end and the outer surface of said cylindrical segment being working surfaces for acting on a tooth and for removing tooth material, the cross section of said tapered end diminishing as the distance from said cylindrical segment increases ; a stem having a first end and a second end, said second end being connected to said cylindrical segment at the end of said cylindrical segment spaced from said tapered and, a second axis extending between said first and second ends of said stem, said first and second axes meeting at an angle of approximately 90° ; and an elongated hand piece having connection means for releasibly gripping said stem, said hand piece including dynamic means for providing sonic vibrations at least along a third axis lengthwise of said hand piece, said sonic vibrations being transmitted to said working tip via said stem when said stem is gripped by said connection means, said second axis and said third axis intersecting at an angle. 25. An endodonctic apparatus as in claim 24, wherein said stem includes an elbow portion. SUBSTITUTE SHEET 26. An endodontic apparatus as in claim 7, wherein said first cylindrical segment is bar and said barbed surface, inclusive of said barb, has an outer diameter in a range o approximately 0.20 millimeters to 0.55 millimeters and said first cylindrical segment, exclusive said barbs, has a diameter in a range of approximately 0.17 to 0.52 millimeters. 27. An endodontic apparatus as in claim 24, wherein the working surface of at least one said tapered end and said first cylindrical segment is barbed. 28. An endodontic apparatus as in claim 27, wherein said tapered end is conical. 29. An endodontic apparatus as in claim 21, wherein said first axis, and an apex of s pointed end, face in a direction generally towards the hand piece. 30. An endodontic apparatus for retrofill cavity preparation, comprising : a tool including a working tip having a first axis, said tip including a tapered e connected to one end of a cylindrical segment, said cylindrical segment and said tapered e being aligned to said first axis, the outer surfaces of both said tapered end and said cylindri segment being working surfaces for acting on a tooth and for removing tooth material, the cr section of said tapered end diminushing as the distance from said cylindrical segment increas stop means positioned proximate the other end of said cylindrical segment, said stop me extending radially of said first axis and beyond the working surface of said cylindrical segme and an elongated stem for connection to a tool holder, one end of said stem being connected said cylindrical segment proximate said stop means. 31. An endodontic apparatus as in claim 30, wherein the working surface of at least one said pointed end and said first cylindrical segment is barbed. SUBSTITUTE SHEET

Inventors: FONG CHENG DAN, FONG, CHENG, DAN
Applicants: MICRO MEGA SA, MICRO MEGA S.A.
Application year: 1993
Main classification: A61C3
IPC codes: A61C1