US RE39174 E1
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.
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 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.
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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.
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This application is the parent of a Divisional Reissue application Ser. No. 10/811,796, filed Mar. 29, 2004.
1. Field of the Invention
The present invention relates generally to endodontic instruments and, more particularly, to root canal files or reamers used in the cleaning of material present in the root canal of a human tooth and for enlarging and shaping the root canal so that it may be prepared for filling and also to the materials necessary to dry, fill and restore the prepared channels.
2. Description of the Related Art
A relatively common but difficult dental procedure is the cleaning, shaping, and filling of the root canal of a patient's tooth. In the performance of a root canal procedure, a hole is first cut in the crown or exposed portion of the tooth, typically either in the biting surface of the tooth, for posterior teeth, or in the side of the tooth on the interior of the jaw for incisor teeth. Small endodontic instruments known generally as root canal files are then used to clean out the material present in the root canal, and to impart a tapered shape to the root canal so that filling material may be inserted into the root canal to seal it. An example of such an instrument, also called a broach, is shown in U.S. Pat. Des. No. 250,544 of Leonard.
Two types of instruments are in general use as root canal files, namely the K-type instrument and the Hedstrom instrument. The K-type instrument is an axially twisted and tapered, triangular or square cross-sectional shaft providing three or four spiral cutting edges along the tapered shaft and a conical tapered tip on the end thereof. An example of a K-type file is disclosed in U.S. Pat. No. 1,307,446 of Kerr. K-type files have recently come to be manufactured with lathe-cut flutes as well. The Hedstrom-type instrument is a lathe-cut file having a round tapered shaft with one, two, or three spiral cutting flutes machined into the shaft all the way to the tip. The main difference resulting from the construction of the two types of files is that the K-type file will cut in either rotational direction, or when moved up and down, while the Hedstrom-type file will cut best when moved up and down in the root canal.
When a root canal is being cleaned and shaped, a series of files having increasing diameters is used to gradually enlarge the root canal. The files are held between the thumb and forefinger of one hand by the dentist. Each file in a set of the known prior art has an identical taper from one end to the other. For example, in a typical K-type file set the taper is 0.32 millimeters on every file over the standard 16 mm length of cutting flutes, or 0.02 mm of taper/mm of flute length. This taper is sometimes referred to as a standard ISO (International Standards Organization) taper. Although these file sets have identical tapers, they come in a number of sizes. The size number characterizing the file is the diameter of the file at the tip in hundredths of a millimeter, and the diameter of the file at the large end is thus 0.32 millimeters greater than this tip diameter. A complete set will include sizes 06, 08, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 70, 80, 90, 100, 110, 120, 130, and 140, while sizes 08-60 will typically be used. Some manufacturers make certain half-sizes, or off-standard sizes.
Hedstrom-type instruments similarly come in sets of increasing size, typically from 0.10 to 1.40 millimeter tip size, flute pitch angle which increases as the instrument tip is approached, thereby decreasing the depth of the flute spaces and increasing the mass of metal in the more fragile tip region. While this feature does add strength to the tips of smaller ground-flute instruments, it creates file tips which are too stiff and inefficient in the larger sizes.
Unfortunately, even twisted-flute #15 files are often not strong enough to withstand the tremendous apical forces which dentists bring to bear when attempting to negotiate calcified canal orifices. As they are pressed into the pulp chamber floor in an attempt to get a “catch” in a calcified canal orifice, these ISO tapered #15 files often buckle, requiring their disposal and the use of yet another #15 file. It is typical that dentists will destroy 10-20 #15 files before they can sneak to the end of these difficult canals.
Another problem countered when using negotiation files of small diameters is the relatively large jump in tip diameter between #10 files and #15 files, a change of 50%. Schilder has addressed this problem in his U.S. Pat. No. 5,017,138 which describes ISO tapered files with tip diameters which increase proportionally in size, providing a series of files with tip sizes 0.10, 0.126, and 0.067 mm in diameter. Maillefer manufactures a non-proprietary file set with half sizes in these smaller instruments, providing clinicians with sizes 0.01, 0.125, 0.15, 0.175, etc., so that progressing between sizes #10 and #15 files is easier.
Root canals are seldom straight and there is always the possibility of causing irreversible damage to roots during shaping procedures, depending on the thinness of the root and severity and with 0.15-0.60 millimeter tip sizes being most commonly used. Both the K-type and Hedstrom files manufactured to ISO standards, whether twisted or lathe-cut, have flute pitches and frequencies which vary little or none in some sizes (large), but quite a bit in other sizes (small). This variation in flute angle or pitch is most perpendicular to the long axis of the file near the shank end, changing to a lessor angle (more in line with the long axis) as the flutes approach the file tip. Only one file has flute angles which vary in the opposite manner, a file disclosed in U.S. Pat. No. 4,674,979 by Jacklich, an ISO-tapered file.
The reason for Jacklich's file design is that ground-flute instruments are not strong enough or stiff enough in the smaller sizes. Ground-flute instruments have their flutes cut into tapered wire blanks which are round in cross-section. This results is the flutes being cut across the grain of the metal, thus achieving less strength than twisted-flute files. Twisted-flute files are formed by first grinding a tapering cross-sectional shape that is triangular, square, or rhomboidal down the length of the wire, in line with the metal grain. Then this tapering wire blank is twisted, causing the corners of the tapered wire blank to become spiral cutting flutes. Because of the twisting process, the metal grain is thus aligned with the helical cutting flutes.
Although stainless steel ground-flute files are of acceptable strength in ISO sizes #20 and larger, they are of inadequate strength in size #'s 06, 08, 10 and 15. In these smaller sizes only the twisted-flute instruments are stiff enough, with a short #15 file being typically used to initially penetrate coronally occluded canals. Jacklich has attempted to circumvent this problem in his ground-flute Hedstrom-type files by creating a location of the root curvatures. If too large a file is advanced too far into a curved root canal, it may easily cut through the side of the root, which is referred to as a perforation of the root, and usually the tooth must then be extracted.
Another cause of root perforation is the inadvertent introduction of large engine-driven Gates-Glidden or Peezo burs into the middle third of thin, curved roots. Quite often, when these burs are new and sharp, the operator will intend to use one of the larger sizes only at the orifice of the canal but will helplessly watch the bur grab the canal walls and pull itself into dangerous depths in the root.
While perforation is probably the worst outcome of mistakes in shaping procedures, there is a more common problem in near-perforations and root weakening caused by overzealous widening of the canal preparation. It is well documented in the endodontic literature that adequate shape in the cervical two-thirds of the canal preparation is mandatory to accomplish adequate cleaning of the canal, to provide necessary control of instruments in the delicate apical regions of the canal, and to effectively obturate the whole root canal space. However, it is difficult to determine the fine line between creating adequate access and dangerous over-instrumentation, as all of these procedures are accomplished in microscopic root canal systems that are hidden from direct view.
Furthermore, if the tip of the file does not follow the curvature of the canal and bores a passage branching out from the root canal, which is referred to as ledging, surgical correction of the problem is often necessitated. It is thus apparent that the art of root canal shaping is one which requires great skill to prevent damage to the tooth and to create a tapered canal preparation conducive to ideal filling of the canal.
The technique used with a conventional set of files having identical tapers to clean and shape the root canal is referred to as the “step-back” technique. A series of file sizes from 08 to 60 (12 instruments) are introduced into the canal from smallest to largest with each successively larger file being used further back from the end of the canal. Additionally, between 4 and 6 sizes of Gates-Glidden or Peezo burs are similarly used in this step-back manner comprising a total of 16 to 18 instruments.
This technique is, at best, a difficult and time-consuming method as the dentist must indirectly gauge the rate of taper in the preparation by the distance interval of step-back of the progressively larger instruments as they fit further back from the canal terminus. As only the ISO taper of 0.02 mm/mm is currently available in standard sizes to dentists in files, irrigation cannulas, condensation pluggers, heat carriers and injection needles, paper points, filling material, and restorative posts, the current shift to canal preparations of greater taper has created great difficulties for dentists who want to enhance their root canal shaping objectives. The skills required, with these relatively non-tapered instruments and materials, to create conservative but adequately tapered shapes in root canals and to easily and ideally fill them usually comes only after treating hundreds of clinical cases.
In my prior U.S. Pat. No. 4,836,780, I disclosed a solution to this shaping problem which involved a series of tapered files with Hedstrom flutes to be used in a push-pull motion, the files having a SAFE EDGE™ or non-cutting surface along one longitudinal side of the instrument. While these variably tapered instruments can create continuously tapered root canal preparations, they are extremely difficult to pull out of the canal by hand because the whole length of the cutting flutes is engaged in the canal, as opposed to standard ISO Hedstrom files which are relatively untapered, engaging less canal length during shaping, and therefore easier to use in a push-pull fashion.
In his U.S. Pat. No. 4,536,159, Roane disclosed a new, more effective method of manipulating ISO-tapered K-type root canal files, wherein the file is lightly rotated in a clockwise direction to thread the file into the canal, after which, with apical force applied, the file is counterclockwise rotated to cut and plane the canal walls. Because the clockwise direction of the flutes causes the file to back out of the canal when it is counter-rotated, the file tip tends to center in the canal just before it cuts, if the apical force being applied to the handle is great enough to keep the file in place. In addition, Roane determined that straight ISO-tapered files can be used in curved roots without risk of perforation as long as rotary cutting motions are used and push-pull motions are avoided. Thus, aggressive rotary shaping of curved canals with unbent ISO-tapered K-type files can be accomplished without ledging or perforation of the canal walls.
While this filing motion would aid the use of variably-tapered K-type shaping files with their challenging full-length engagement of the canal walls, it became apparent during my testing that as files were given greater tapers, they became more likely to perforate curved roots, due to the increasing stiffness attendant with the larger shank diameters of the more tapered files in the series. Additionally, the standard “hour-glass” file handle disclosed in Roace's patent, while not ideal for rotary cutting techniques with ISO-tapered files, is actually inadequate, due its shape (designed for push-pull filing motions) and narrow diameter, for rotary cutting with files of greater taper. The SAFE EDGE™ feature, while eliminating lateral root perforation when using push-pull filing motions, by definition excludes the use of rotational cutting motions, as the safe-edge would then move to all surfaces of the canal, thereby negating the safety feature's function in curved roots.
Other prior art to be mentioned here is that relating to the non-standardized nature of conventional irrigation cannulas, paper points, gutta percha points, obturation carriers, obturation pluggers, heat carriers, backfillers, and restorative post systems when used in the creation and treatment of tapered root canal preparations. Existing irrigation cannulas are parallel-sided, with different designs of opening at their tips. These are used to wash the inside of root canal systems with solutions with the intention of debriding, disinfecting, and cleansing the canal space prior to sealing it. Unfortunately, these irrigating cannulas are limited in their ability to clean the ends of root canal systems as they are so small in diameter. Research to date shows that irrigating cannulas are only effective to the extent that they can penetrate the canal, usually to midroot, leaving the important apical third of the canal unaffected.
Dentists are able to overcome this problem by the use of small patency files which are used to clear debris from the end of the canal, but which also displace irrigant from this apical region of the canal during its use, allowing fresh irrigant back into the apical region after the file's withdrawal. As the files are relatively untapered (ISO 0.02 mm/mm) this irrigant exchange is limited.
When the canal has been cleaned and shaped, it is dried with absorbent paper points of varying size and taper. In canals which have been tapered with burs and files in a step-back fashion, it is often necessary to use several different sizes of paper points to dry the whole length of the canal, small paper points apically, larger paper points for the middle of the canal, and sometimes even larger paper points for the cervical region of the canal. Furthermore, as the tapers of the paper points seldom match the taper of the canals, there may be moisture left on parts of the canal walls after drying procedures.
There are several methods of sealing root canal systems, most of them using a rubber-like material called gutta percha. When used as a tapered gutta percha cone, this material is compacted into the canal with pluggers, or the gutta percha material may be placed as a coating on an obturating carrier, which is warmed to soften the gutta percha and placed in the canal, with the carrier compacting the material into the canal space.
Currently, the shapes of filling materials and obturating carriers do not match the tapering shapes of prepared canals either. When the step-back technique of canal shaping is used, the final shape of the canal preparation can only be discerned indirectly, by the increments that each larger instrument fits further back from the terminus of the canal, a difficult skill learned only after much experience. As the prepared taper is often obscure to the clinician, it is likewise difficult to pick an appropriately tapered gutta percha point or obturating carrier with which to seal the canal. If the selected obturating device or gutta percha point is too tapered, they will bind in the canal short of its terminus, causing the crucial apical seal to be inadequate, allowing leakage and failure of the endodontic treatment. If the obturating carrier or material is too narrow, little hydraulic pressure will be exerted on the filling materials in the cervical two-thirds of the canal during condensation procedures, and lateral or accessory canals in that region of the canal may not be sealed, again increasing the chance for failure of treatment.
While there are many techniques of filling root canals, it is generally recognized in the field of endodontics that those methods which warm and soften the gutta percha filling material, allowing it to be thoroughly compacted into all the nooks and crannies of root canal systems, are superior to those techniques which do not thermoplasticize the gutta percha prior to condensation.
The classic technique was described by Schilder in 1969, vertical condensation of warm gutta percha. In this technique an appropriately tapered gutta percha cone is fit and cemented in the prepared canal, after which a flame-heated or electrically-heated gutta percha heat carrier is used to sear off the gutta percha cone at the orifice level of the canal. By pressing the softened gutta percha into the canal with an appropriately sized vertical condensation plugger, the first wave of condensation is initiated, filling any lateral canals present in that region in the primary canal. The heat carrier is then reintroduced into the canal, penetrating the gutta percha several millimeters, heating the apical mass, and removing a portion of it so that the next wave of condensation may occur deeper in the root. These heating and compacting cycles continue until the final wave of condensation which ends 5-7 mm from the canal terminus.
Typically it takes 3-7 waves of condensation to reach this end point. At this point the clinician must either place a retentive post in the coronal canal space or backfill it with gutta percha. Backfilling can be done by heating 3-8 small pieces of gutta percha and sequentially packing them into the canal, or by syringing alloquates of pre-heated gutta percha from a gutta percha gun and compacting them with pluggers. Downpackng with multiple waves of condensation and backfilling in the manners described require at least 7-10 different instruments, fairly extensive training of the dentist and chairside assistant, and 15-30 minutes of clinical time. Furthermore, these condensation pluggers and heat carriers lack a correlating mechanism to match their sizes to the taper of the canal preparation.
The disadvantages and limitations of the background art discussed above are overcome by the present invention. The present invention differs significantly and advantageously from the cleaning, shaping and filling technology discussed above in nine respects.
First, rather than using a large series of files of differing sizes but the same taper, as is the case when using standard ISO-tapered files, the present invention often allows full root canal shaping to be accomplished with as little as a single file from its set of variably-tapered shaping files.
Second, instead of indirectly creating a tapering canal preparation with the difficult and time-consuming serial step-back shaping technique necessary with ISO-tapered files, the present invention requires only that the shaping file or files be worked to the terminus of the canal, thereby completing the preparation.
Third, the present invention provides for variably-tapered negotiation files, allowing optimally varied stiffnesses as the tips of the instruments in the series increase in diameter. Furthermore, these files of increasing taper have small, even increases in tip diameter allowing more passive negotiation to the terminus of constricted canals.
Fourth, increasing tapers of these files can be used without increasing risks of root perforation or weakening, by progressively shortening the cutting flute length as the files become more tapered.
Fifth, one version of these tapered files can be efficiently used with rotary cutting motions without increased breakage, due to their varied flute pitch and sharpness along the length of the instruments.
Sixth, safe function of these files in curved canals is also gained through the use of nickel-titanium (Nitinol™), an alloy which exhibits extreme flexibility and elastic memory.
Seventh, the present invention differs significantly from prior art in the pear-like shape of the file handles, a design which enhances the application of pushing and rotational forces to the file by the dentist's fingers.
The eighth improvement over existing art is the provision of irrigating cannulas, paper points, filling materials and instruments, and restorative posts which are contoured to match the pre-defined canal preparations created by the variably-tapered shaping files, thereby matching corresponding ones of the shaping files.
Ninth, the present invention includes a technique whereby canals can be more simply ideally obturated in all their complexity with the aforementioned tapered filling instruments and materials used in a single inward wave of condensation, followed by a single backfilling wave to complete the fill if a post is not to be placed in the canal.
With regard to the first two features of the present invention, several advantages over the art are achieved by using variably-tapered files. The purpose of endodontic shaping procedures is to create a continuously tapering preparation which is narrowest at the end of the canal, and widest near the crown of the tooth. By using files that vary in their tapers, it has been determined that root canals may often be prepared by using a single shaping file instead of the 16 to 18 files required by conventional ISO-tapered instruments. While it is readily apparent that the use of only one tool instead of 16 to 18 tools is desirable from a standpoint of efficiency, it should also be noted that the present invention provides ideal root canal shaping results with less training and experience. Rather than creating a tapered canal shape by the difficult and time-consuming step-back technique, the present invention simply requires that a shaping instrument of appropriate taper be worked to the full length of the canal. In addition to the greatly improved ease and simplicity of shaping canals with a single instrument, this provides, for the first time, a pre-defined shape throughout the full length of the canal. One of the most important advantages provided by pre-defined root canal preparations is the resultant ability to optimize cleaning and filling procedures in root canal systems. Since the design of files taught by the present invention involves different tapers, the tips of the shaping files are not used to cut a path in the canal as in files with standard tapers. Whereas standard ISO file sets have the same tapers but increasing tip diameters in the sequence of files, the tip diameters of a set of shaping files constructed according to the present invention may be the same between files of different tapers. There may also be different sets of these shaping files which differ in their tip diameters, i.e. one set of shaping files with tapers of 0.04, 0.06, 0.08, 0.10, and 0.12 mm/mm and the same 0.2 mm tip diameters; another set of shaping files with the same range of tapers but with 0.35 mm tip diameters, etc. And finally, the present invention includes sets of shaping files with similar non-ISO tapers which vary by evenly or proportionally increasing tip diameters.
The third difference in the present invention is the provision for variably-tapered negotiation instruments with even or proportional increases in tip diameters. This file set has tapers which range from 0.1 mm/mm to 0.5 mm/mm, thereby imparting twice the usual stiffness in the critical initial negotiation file with a 0.15 mm tip diameters. After the canal has been penetrated to midroot by the rigid 0.04/0.15 (taper/tip diameter), the dentist can either progress downward in size to the 0.03/0.125, the 0.02/0.10, and finally the 0.01/0.075 or drop down to the 0.01/0.075 taken to full length and then work up in the file sizes until the 0.04/0.15 goes to length. When the files of narrower taper are embedded at least halfway into a canal, the canal walls will then support narrower less robust file sizes and prevent them from buckling. Therefore this set of negotiating files should kink less upon initial entry, and provide greater tactile awareness and control of instruments in the tortuous apical regions of canals. Additionally, the 0.025 mm increases in tip size circumvent the problematic 50% jump in tip diameters between ISO-standard file sizes #10 and #15. Progressing to full length in constricted canals with this negotiating file set, from sizes 0.075 mm to 0.10 mm to 0.125 mm to 0.15 mm, is effortless as a result.
The fourth important difference between the present invention and the art is that shaping files constructed according to the teachings of the present invention can be safely used in curved canals and/or thin roots in spite of their greater rates of taper. This is accomplished very effectively by the specification of progressively shorter flute lengths as files in a set have progressively greater tapers, thereby limiting their maximum flute diameters. Without this feature, the shank-end flute diameters of variably-tapered shaping files become wider and stiffer as the tapers of these instruments increase, and their potential for lateral perforation or weakening of the root increases as well.
While limiting the maximum flute diameter of these increasingly tapered shaping files allows their safe use, this feature is extremely important in a broader sense. Using a single shaping file instead of the usual 15-18 instrument set means that the final shape through the full length of that canal is pre-defined, unlike the shaping result when six different sizes of Gates-Glidden burs are used progressively shallower in the coronal portions of the root canal. It is extremely common for Gates-Glidden and Peezo burs to be used too deeply in thin roots, risking weakening and perforation. Simply limiting the maximal flute diameters of shaping files allows, for the first time in the field of endodontics, enlargement of the coronal two-thirds of a canal to an extent that is exactly adequate to clean the tiny apical regions of the canal and to maintain control of shaping and filling instruments in that region, but not a bit larger. The present invention includes this feature applied to the variably-tapered Hedstrom-flute shaping file shown in my U.S. Pat. No. 4,836,780 and to all other types of shaping instruments as well, whether they are used by hand or with sonic, ultrasonic, or mechanical handpieces.
Fifth, safety and efficiency when these shaping files are used with rotary cutting motions is gained in the present invention by longitudinally varying the pitch and relative sharpness of cutting flutes. When shaping files are used with rotary cutting motions two primary problems are encountered, potential for breakage and slowness of cutting. This is overcome in the present invention by varying the flute pitch from an in-line reamer-like angle at the shank end of the instrument to a more perpendicular K-type flute angle at the file tip. Instead of, or in addition to the above, the relative sharpness of the cutting flutes is varied along the length of the files, being sharpest at the strong shank end to allow for aggressive cutting by the wider flutes, and dullest near the smaller, more fragile tip of the file so these flutes can easily release from the canal wall during rotation, thereby preventing file breakage which can occur when the tip binds.
Sixth, functional safety when using tapered shaping files in curved canals is enhanced through the use of the alloy nickel-titanium (Nitinol™. This unusual metal exhibits stress-induced phase-transformation of its crystal lattice structure resulting in characteristics of superelasticity, allowing large-diameter Nitinol files to work around root canal curvatures that would be impossible with stainless steel. Nitinol's elastic memory also allows, in one arrangement of the invention, curvatures to be preset in the file during the manufacturing process. By heating and cooling files made of this metal, different curvatures can be present in the metal so that the desired shape is “remembered”, allowing the file to straighten in the relatively uncurved coronal portion of canals and recurve itself when the file tip moves deeper and encounters apical root canal curvatures. When added to a Hedstrom-fluted taper file, a preset file bend directed toward its safe edge causes the Nitinol version of this shaping instrument to automatically seek the inside of canal curvatures with its non-cutting side, thereby effortlessly preventing lateral perforation.
The seventh aspect of the present invention involves an improvement in the shape of the handle provided for files of the invention. Standard file handles conventionally have a narrowed waist portion with enlarged diameters at both ends of the handle. This is to accommodate a push-pull action in conventional use of the file. Handles in accordance with the present invention have an end diameter smaller than the waist of conventional file handles, and they taper to a larger-than-conventional diameter near the file shank, where the file is embedded in the handle. Since the file is designed to cut with apically directed rotary forces, the shape of the handle enhances operator comfort and reduces the force necessary to cut the desired shape into the root structure around the original canal. This “pear-shaped” handle also enhances the use of standard ISO K-type files used with apically-directed cutting motions.
Eighth, one of the most important improvements over existing art is the provision of a coherent system of irrigating cannulas, paper points, filling materials and instruments, and restorative posts which relate to the shapes of corresponding shaping files and thus to the pre-defined canal shapes created by these tapered files. Specific and isolated improvements in root canal preparation and filling techniques often create more procedural problems than they solve, as clinicians must somehow fit this new technique nuance into their usual procedural flow. The present invention incorporates an integrated system of variably-tapered shaping files and similarly-tapered implements and materials, which work together. Any canal which has been shaped by an 0.06 mm/mm tapered shaping file can, without further thought, be cone-fit, dried, obturated and restored with instruments and materials manufactured to the same shape, thereby enhancing the safety, ease of use, and results of the clinical practice of endodontics.
Finally, the present invention includes an obturation technique which utilizes variably-tapered electric heat pluggers to downpack and backfill root canals in single waves of condensation, dramatically reducing the technical complexity and number of instruments needed over the traditional Vertical Condensation of Warm Gutta Percha Technique. There are two embodiments of this invention which are useful, one to be used in canals shaped and cone fit by traditional means, the other to be used in the pre-defined preparations created by variably-tapered shaping files. In the first instance, serial step-back instrumentation procedures are used to impart a tapered shape to a given canal after which a non-standardized gutta percha cone is fit in the canal and cemented with sealer after the canal is dried. Instead of using a standard untapered electric heat carrier, 5 pluggers, and 4-5 waves of condensation as needed in the Vertical Condensation of Warm Gutta Percha technique, the Continuous Wave of Condensation technique requires only a single tapered electric heat plugger and a single movement of the heat plugger through the pre-fit gutta percha cone to accomplish the same quality of result. The key to this technique is that the electric heat carrier is used as a plugger, and the heat pluggers in this set have the same shapes as the non-standardized gutta percha points which are fit in tapered canal preparations. Generally speaking, clinicians fit gutta percha points with slightly less taper than the root canal preparation, therefore a heat plugger with the same taper as the gutta percha point will by definition fit that canal shape.
In the other embodiment of the present invention, the electric heat pluggers have the same or nearly the same configurations as the variably-tapered shaping files. This can provide a more ideal obturation result as canal shapes are more precisely controlled throughout their length with this shaping method, therefore insuring a more precise match of canal shape and heat plugger. Because of this close fit of these pluggers to the pre-defined canal shapes the hydraulic pressures exerted on the thermosoftened gutta percha and sealer cement are more effective in their ability to fill lateral and accessory canals off the primary canal. As the heat plugger is moved through the recently softened gutta percha, it eventually binds the canal short of its terminus and the downpack is completed. The tip diameter of the heat plugger determines this apical endpoint of the downpack and it is chosen to terminate 3-5 mm from the canal terminus.
In the second part of this filling technique, there are pre-formed gutta percha backfilling plugs, which match the vacant space left after the downpack is completed, and a different electric heat carrier/plugger device with which to heat soften and compact the backfilling plug into the coronal aspect of the canal. In preparation, the narrow heat carrier tip is extended beyond the plugger tip and is inserted into a groove or passage in the backfilling plug after which a short burst of heat fuses the plug to the backfilling device. The device with its attached gutta percha plug is then placed cold into the empty canal region and, as a heating cycle is initiated, the heat carrier tip is withdrawn from the plug as the plugger is simultaneously used to push the recently softened plug into the canal space.
A better understanding of the present invention may be realized from a consideration of the following detailed description, taken in conjunction with the accompanying drawings in which:
Views A and B of
Before describing the present invention, it may be helpful to discuss briefly the root canal procedure as shown in
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Referring now to
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Another problem shown in
While any or all of the shaping instruments described in the present invention may be mounted in a latch-grip shank 81, as seen in
The embodiment as shown in
This flute design answers two critical challenges encountered when using a single shaping instrument to create a canal shape previously imparted with from 15 to 18 conventional instruments. Optimal function of this type of instrument requires enhanced cutting efficiency and flexibility at the larger shank end, and maximal strength at the more fragile file tip. Fortunately, tapered canal shaping objectives require less dentin removal apically; therefore the optimal tapered shaping file design can sacrifice apical cutting efficiency for added strength. The K-type flute angle provides this.
In this embodiment, the flute pitch is 0.5 flutes/mm (one flute in two millimeters) adjacent the largest diameter flute 62 and two flutes/mm or four flutes in two millimeters adjacent the tip 64. The ratio of flute pitch at the shank tip to flute pitch at the tip shank (the overall flute pitch ratio) is four in the
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
Views A and B of
As may be seen from a comparison of
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
Views A through E of
View F of
Turning now to
View 17C of
View 17D of
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
View 17G of
Finally, view 17I of
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.
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.