Abstract:
An endodontic file comprising an elongated, flexible metal, the file having a working portion for cutting or abrading biological material, the working portion comprising a proximal portion and a distal portion, the proximal and distal portions having different cross-sectional flute or core patterns and associated cutting edges.

Description:
[0001]     This application is a Continuation-in-Part of U.S. Ser. No. 10/756,599, filed Jan. 12, 2004, entitled ENDODONTIC INSTRUMENT AND INSTRUMENT SYSTEM, which claims the benefit of and priority to U.S. Provisional Application No. 60/439,479, entitled “ENDODONTIC INSTRUMENT”, filed Jan. 13, 2003, the entire disclosures of which are hereby incorporated by reference as if set forth in their entirety for all purposes. This application also claims the benefit of and priority to U.S. Provisional Application Ser. No. 60/687,297, filed Jun. 6, 2005, entitled ENDODONTIC INSTRUMENT WITH MULTIPLE FLUTE PATTERNS, the contents of which are hereby incorporated by reference as if set forth in its entirety for all purposes. 
     
    
     BACKGROUND  
       [0002]     This invention relates generally to endodontic instruments known as endodontic files, used by dentists when performing root canal procedures. A root canal procedure is a common dental procedure for treating or preventing a dental abscess. During a root canal procedure, the infected nerve and pulpal tissue are removed from the root canal of the involved tooth. The root canal is then cleaned by shaping or reaming the root canal with endodontic files to produce a clean environment to receive a root canal filling material. The standard filling material, which has been used for over fifty years, is an inert material called gutta-percha.  
         [0003]     Endodontic files are used to remove the contents of the root canal and to prepare or shape the root canal prior to filling it. Endodontic files may be designed to be manually manipulated by the fingers of a dentist or to be engine driven by a rotating hand piece, which rotates the file during use. Endodontic files typically consist of a tapered distal working portion containing a plurality of helical spiraled flutes, a shaft portion located proximal to the working portion, and a handle located on the proximal end of the instrument. The flutes form planing or cutting surfaces, which dislodge and remove the infected tissue within the root canal being treated. For all currently available tapered endodontic files the helical or spiral flutes turn continuously along the entire working portion of the file.  
         [0004]      FIGS. 1 and 2  show a prior art endodontic file  10  that is representative of the type currently in use. File  10  includes a handle  12  at a proximal end  14 , a shaft portion  16 , and a working portion  18  that tapers toward a distal end  20 . Working portion  18  is formed of a plurality of helical or spiral flutes  22  that form cutting surfaces  24  (also known as radial lands) supporting cutting edges, as seen most clearly in the cross-sectional view of  FIG. 2 . Flutes  22  extend continuously along working portion  18 . File  10  may be manipulated by hand or be engine driven to rotate so that the edges of cutting surfaces  24  remove infected tissue from the root canal.  
         [0005]     Because root canals are seldom straight, but usually curved or twisted in multiple planes, it is important that endodontic files be flexible so that the file can follow the curved canal to its terminus during the cleaning process. Another advantage to having endodontic files with enhanced flexibility is that file breakage during the cleaning process of the root canal is greatly reduced. The recognized need for flexible endodontic files has led to the use of nickel-titanium alloys as the preferred material of choice for constructing endodontic files.  
         [0006]     Understanding that file breakage during a root canal procedure is an undesired event and its prevention is critical to a successful root canal procedure, providing an endodontic file with a resistance to breakage would be of great benefit to the field of endodontics.  
         [0007]     File breakage generally occurs from two causes. The first cause is cyclic fatiguing of the instrument material caused by repeated bending of the file. The incidence of cyclic fatigue file breakage is inversely related to file flexibility, therefore as instrument flexibility increases, cyclic fatigue file breakage decreases. The second cause of file breakage is the application of excessive torque to the endodontic file leading to torque failure. Such excessive torque is caused, at least in part, by the fact that substantially the entire length of the file working portion is in contact with the canal wall.  
         [0008]     Some current cleansing and shaping techniques used to prepare the root canal employ numerous endodontic files having a continuously tapered helical fluted working portion. The numerous files used during a root canal procedure may have different tip diameter sizes and/or tapers to allow the different files to clean different regions of the root canal. However, such current endodontic files encounter the problems discussed above.  
         [0009]     The following patents relate to existing endodontic instruments and/or methods of manufacturing: U.S. Pat. Nos. 6,968,619, 4,934,934; 5,464,362; 5,628,674; 5,653,590; and 6,074,209. All the foregoing patents are hereby incorporated by reference in their entireties for all purposes.  
         [0010]     It would be an improvement in the art of endodontics to provide an endodontic file that has enhanced flexibility to reduce the likelihood of breakage. It would be a further improvement to provide an endodontic file having limited or dedicated cutting regions along the working portion of the file to limit the root canal surface area that is engaged by the endodontic file and to control which portion of the root canal is shaped and/or prepared. Decreasing the surface area of the endodontic file in contact with the root canal wall would effectively reduce the frictional torque applied to the instrument and would decrease the incidence of torque failure breakage  
       SUMMARY  
       [0011]     As will be appreciated by persons skilled in the art from the teachings herein, the inventive subject matter disclosed herein contemplates novel endodontic files for shaping and/or preparing a root canal during a root canal procedure wherein there are variable cutting properties along the working portion of the shaft to achieve desired properties for cutting, debris removal, strength, flexibility, and/or other operational parameters.  
         [0012]     The files disclosed herein generally have a proximal shaft portion connected to a handle portion and a distal working portion. The file may be manipulated by the fingers of an operator or inserted into a rotary engine driven hand piece.  
         [0013]     In certain embodiments, working portion of the file may include novel arrangements of multiple tapered cutting segments separated by non-cutting segments. The cutting segments have a cutting edge formed by a plurality of helical flutes. Each non-cutting segment preferably has a diameter that is significantly smaller than the diameter of the adjacent cutting segments. This arrangement provides overall flexibility of the file and increases the resistance to cyclic fatigue breakage. This arrangement further controls or limits which areas of the root canal are shaped and/or prepared during file use. The non-cutting segments limit the surface area of the root canal that is engaged by the cutting segments of the file. The cutting segments are located and arranged along the working portion to control which portion of the file actively shapes and/or prepares the root canal. The cutting segments may have a substantially continuous taper. Alternatively, the taper of each cutting segment may vary.  
         [0014]     In other possible embodiments, the cutting segments may have a non-circular geometric configuration and may be formed as straight and oriented substantially parallel to the long axis of the file rather than formed as helical or spiraling cutting segments. Such embodiments prevent the file from self-feeding into the root canal.  
         [0015]     In other possible embodiments, an endodontic file forms part of a series of endodontic files to shape and/or prepare a root canal. Each file in the series may use novel files disclosed herein. For example, two or more files in a set may have cutting segments and non-cutting segments strategically placed in different regions along the working portion of the file to allow each file in the system to shape and/or prepare different portions of the root canal.  
         [0016]     The present invention provides an endodontic file for use in root canal treatment in which the cutting segments are located along the working portion in a manner to correspond with a portion of a root canal that is to be actively cut. For example, the cutting segments and non-cutting segments may be of any length and may by of any number.  
         [0017]     In certain embodiments, the non-cutting segments may have a diameter that is substantially less than the diameter of the cutting segments in order to provide flexibility and to control which region of the root canal is shaped or prepared by the file.  
         [0018]     To illustrate still further embodiments consistent with the principle of providing a working shaft with variable properties along the working shaft, a working shaft may have at least two different cross-sectional core or flute patterns along the working portion of the file. For example, the cutting flutes on the distal end of the working portion may have a radial landed “U-shaped” cross sectional design and the flutes on the proximal end may have a non-radial landed “triangular-shaped” cross sectional design. Any combination of multiple cross sectional flute geometries, radial landed or non-radial landed, may exist on the working portion.  
         [0019]     These and other embodiments are described in more detail in the following detailed descriptions and the figures.  
         [0020]     The foregoing is not intended to be an exhaustive list of embodiments and features of the present invention. Persons skilled in the art are capable of appreciating other embodiments and features from the following detailed description in conjunction with the drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]      FIG. 1  is a view of a prior art endodontic file.  
         [0022]      FIG. 2  is a cross-sectional view of the endodontic file of  FIG. 1  taken along line A-A.  
         [0023]      FIG. 3  is a view of one embodiment of an endodontic file according to the inventive subject matter disclosed herein having multiple tapered cutting sections.  
         [0024]      FIG. 4  is a view of another inventive embodiment of an endodontic file of the present invention having a non-cutting section at the distal end of the file.  
         [0025]      FIG. 5  is a view of another inventive embodiment of an endodontic file having straight cutting sections.  
         [0026]      FIG. 6  is a cross-sectional view of the endodontic file of  FIG. 5  taken along line B-B.  
         [0027]      FIG. 7  is a view of an inventive endodontic file system comprised of plural endodontic files each having cutting sections located at different locations along the working portion of the file.  
         [0028]      FIG. 8  is a view of another inventive embodiment of an endodontic file system showing an alternative arrangement of cutting sections along the working portion of the file.  
         [0029]      FIG. 9  is a view of another inventive embodiment of an endodontic file in which each cutting segment has a different taper.  
         [0030]      FIG. 10  is an illustration of another inventive embodiment of an endodontic file.  
         [0031]      FIG. 11  is an illustration of the cross-sectional flute pattern through line B-B of  FIG. 10 .  
         [0032]      FIG. 12  is an illustration of the cross-sectional flute pattern through line C-C of  FIG. 10 .  
         [0033]      FIGS. 13-20  are each illustrations of example cross-sectional flute patterns according to the inventive subject matter disclosed herein. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0034]     Certain representative embodiments of the present invention are shown in  FIGS. 3-9 , wherein similar features share common reference numerals.  
         [0035]      FIG. 3  shows one embodiment of an endodontic file  30  of the present invention. File  30  may include a handle  32  located at a proximal end  34 , a shaft  36 , and a working portion  38  extending to a distal end  40 . Working portion  38  may be formed of a plurality cutting segments  41  formed of helical or spiral flutes  42  that form cutting edges  44  and separated by non-cutting segments  46 . Cutting segments  41  may be of any desired shape but are shown in this embodiment as being tapered in a direction from proximal end  34  toward distal end  40 . Non-cutting segments  46  are shown in this embodiment to have a smooth circular cross-section having a diameter that is less than the diameter of the adjacent cutting segments  41 . The relationship between cutting segments  41  and non-cutting segments  46  provide flexibility to file  30  to eliminate or reduce the chance of breakage as working portion  38  follows any curved and/or twisted portions of the root canal.  
         [0036]     In addition to providing flexibility, file  30  provides control over which portion or portions of the root canal are shaped and/or prepared. This is accomplished by the location of cutting segments  41  along working portion  38 . Cutting segments  41  may be located along working portion  38  at selected locations depending on which areas of the root canal are to be shaped and/or prepared. For example, in the embodiment of  FIG. 3 , only the portions of the root canal adjacent cutting segments  41  are shaped and/or prepared. The embodiment of file  30  shown in  FIG. 3  shows cutting segments  41  located along working portion  38  in a spaced arrangement in which a cutting segment  41  is located at distal end  40 .  FIG. 4  shows another embodiment of an endodontic file similar to file  30  of  FIG. 3  in which like parts will be given like reference numbers indicated with a prime (′). Thus, file  30 ′ includes cutting segments  41 ′ located and arranged along working portion  38 ′ so that a non-cutting segment  46 ′ is located at distal end  40 ′. It should be further noted that other aspects of working portion  38 ,  38 ′ may vary. For example, although only three cutting segments  41 ,  41 ′ are shown in  FIGS. 3 and 4 , the number of cutting segments  41 ,  41 ′ may vary. Additionally, the length  48 ,  48 ′ of cutting segments  41 ,  41 ′ and/or the length  50 ,  50 ′ of non-cutting segments  46 ,  46 ′ may vary.  
         [0037]      FIGS. 5 and 6  show another embodiment of a file  52  that includes a handle  54  located at a proximal end  56 , a shaft portion  58 , and a working portion  60  extending to a distal end  62 . Working portion  60  may be formed of a plurality cutting segments  64  each having a geometrical shape that forms a cutting edge  66  and separated by non-cutting segments  68 . In this embodiment, cutting segments  64  may have a non-circular shape and are shown as being triangular in cross section, which core structure is shown in  FIG. 6 . However, it should be understood by those skilled in the art that the invention is not limited to cutting segments having a triangular shape and that other geometric shapes may be contemplated. Preferably, the geometric shape of cutting segments  64  form cutting edges  66  that are substantially parallel to the long axis  70  of file  52 . Non-cutting segments  68  are shown in this embodiment to have a smooth circular cross-section having a diameter that is less than the cross-sectional shape of the adjacent cutting segments  64 . Cutting segments  64  have a length  72  and non-cutting segments  68  have a length  74  both of which may vary. The relationship between cutting segments  64  and non-cutting segments  68  provide flexibility to file  30  to eliminate or reduce the chance of breakage as working portion  60  follows any curved and/or twisted portions of the root canal.  
         [0038]      FIG. 7  shows a file system  76  that includes a series of individual files  78 ,  80 , and  82  being of substantially equal length, each file having cutting segments and non-cutting segments strategically located along the file to allow each file to shape and/or prepare a different region of the root canal and to divide the workload of shaping and/or preparing the root canal among the files in the file system  76 . For example, in the embodiment shown in  FIG. 7 , file  78  may include multiple cutting segments  84  separated by non-cutting segments  86  located along working portion  88 . File  80  may include cutting segments  90  and non-cutting segments  92  located along working portion  94 . Working portion  94  extends over a greater portion of file  80  than working portion  88  of file  78 . Additionally, the lengths of cutting segments  90  and non-cutting segments  92  may vary so that they may overlap with cutting segments  84  and non-cutting segments  86  of file  78 . File  82  may have cutting segments  96  and non-cutting segments  98  located along working portion  100 , which extends over a greater portion of file  82  than working portion  94  of file  80  or working portion  88  of file  78 . In a manner similar to files  78  and  80 , the length of cutting segments  96  and non-cutting segments  98  may vary so that they may overlap with cutting segments  90  and non-cutting segments  92  of file  80  and cutting segments  84  and non-cutting segments  86  of file  78 . The cutting segments  84 ,  90 ,  96  of individual files  78 ,  80 ,  82  are arranged so that, when taken together, they effectively form one continuous cutting segment covering the entire working portion  100 .  
         [0039]      FIG. 8  shows an alternative file system  102  that includes a series of individual files  104 ,  106 , and  108  being of substantially equal length. Similar to files  78 ,  80 ,  82  in  FIG. 7 , each file  104 ,  106 ,  108  have cutting segments and non-cutting segments strategically located along the file to allow each file to shape and/or prepare a different region of the root canal and to divide the workload of shaping and/or preparing the root canal among the files in the file system  102 . However, the cutting segments and non-cutting segments of files  104 ,  106 ,  108  are arranged in an alternative manner. For example, file  104  may include multiple cutting segments  110  separated by non-cutting segments  112  located along working portion  1   14 . File  106  may include cutting segments  116  and non-cutting segments  118  located along working portion  120  so that a non-cutting segment  118  is located at distal end  121 . Working portion  120  extends over a greater portion of file  106  than working portion  114  of file  104 . Additionally, the lengths of cutting segments  116  and non-cutting segments  118  may vary so that they may overlap with cutting segments  110  and non-cutting segments  112  of file  104 . File  108  may have cutting segments  122  and non-cutting segments  124  located along working portion  126 , which extends over a greater portion of file  108  than working portion  120  of file  106  or working portion  114  of file  104 . A non-cutting segment  124  is located at a distal end  128 . In a manner similar to files  104  and  106 , the length of cutting segments  122  and non-cutting segments  124  may vary so that they may overlap with cutting segments  116  and non-cutting segments  118  of file  106  and cutting segments  110  and non-cutting segments  112  of file  104 . The cutting segments  110 ,  116 ,  122  of individual files  104 ,  106 ,  108  are arranged so that, when taken together, they effectively form one continuous cutting segment covering the entire working portion  126 . The staggered cutting segments and non-cutting segments of the files of each system  76 ,  102  have been described as overlapping. However, it is within the scope of this invention that the staggered cutting segments of the related files in each system  76 ,  102  do not overlap. Regardless of whether or not the cutting segments overlap the files in both systems  76 ,  102 , when taken together, form a cutting segment along the entire working portion.  
         [0040]      FIG. 9  shows an alternative embodiment for a file  130  having variable tapered cutting segments for added flexibility. In this embodiment, the percentage taper of one cutting segment may be different from the percentage taper of the other cutting segments. For example, first cutting segment  132  may have an 8% taper, second cutting segment  134  may have a 6% taper, and third cutting segment  136  may have a 4% cutting taper.  
         [0041]     It should be understood by those skilled in the art that either file system  76 ,  102  may be comprised of files having tapered cutting segments, variable tapered cutting segments, or geometrically shaped cutting segments.  
         [0042]      FIGS. 10-20  illustrate still further how at least two different cross-sectional flute patterns of any shape may exist on the working portion.  FIG. 10  shows the present inventive file  221  with two different cross-sectional flute or core patterns ( 222   a  and  222   b ) located contiguously along long axis of the working portion of the file. Proximal working portion  214  has a different cross-sectional flute pattern than the distal working portion  212 . The cross-sectional flute pattern for distal working portion  212  is shown in  FIG. 11 , which is taken through line B-B. The cross-sectional flute pattern for working portion  214  is shown in  FIG. 12 , which is taken through line C-C. (In these and other cross-sectional views in the Figures, the circle drawn around the illustrated structure is not intended to represent additional structure, but rather illustrates the radial area capable of being cut by the encircled core structure, consistent with how those in the art illustrate endodontic file cross-sections.) The cross-sectional flute pattern through line B-B is different than the cross-sectional flute pattern through line C-C.  
         [0043]      FIG. 11  shows a cross-sectional flute pattern with a cutting flute  215 . The cutting flute  215  defines a core having generally a tri-spoke configuration. Each of the spoke like sections of the core extends from a central portion of the core and supports cutting edges  217   b . The outer surfaces  219  between the cutting edges on a spoke extend generally are known as “radial-lands.” It is noted that in some configurations, only one of the edges  219  need be a cutting edge.  
         [0044]     The flute pattern  215  defines a core section  222   a  or  222   b , respectively for the proximal and distal working portions, and the flute pattern may vary from one section other or generally be the same pattern.  
         [0045]      FIG. 12  shows a cross-sectional flute pattern defined by cutting flute  215  and a cutting edges  217   a . In this embodiment, the radial lands have been reduced to apices on a triangular core, which are the cutting edges  217   a , and therefore do not extend circumferentially to any substantial degree. Accordingly, this configuration provides a core without radial lands  
         [0046]     The helical flutes  215  in the embodiment shown provide helical cutting edges that extend along the long axis of the working portion continuously from one cross-sectional region  212  into another.  
         [0047]     Although the Figures show only two different portions defining the working portion, there may be a third portion or any number of additional portions wherein such additional portions differ from an adjacent or contiguous proximal or distal portion. Therefore the use of the terms “proximal portion” and “distal portion” are not meant to imply that there are only two portions in any given file or that the portions are located at the most proximal or distal portions of a file. The advantage to multiple cross-sectional flute patterns allows for an endodontic instrument to have more strength in certain areas of the file where it is needed most and to have a more aggressive cutting flute in other areas, as persons skilled in the art will recognize from the teachings herein.  
         [0048]      FIGS. 13-20  show many examples of cross-sectional flute patterns that persons skilled in the art will recognize to provide various properties, such as more aggressive cutting, lower torque, higher strength etc. Some are with radial lands, and some without radial lands.  FIGS. 13, 15 ,  17 ,  18 , and  19  show flute patterns with radial lands;  FIGS. 14 ,  16 , and  20  show flute patterns without radial lands. The cross-sectional flute patterns shown in  FIGS. 13-20  are for example only and the inventive subject matter is not restricted to the cross-sectional flute patterns shown.  
         [0049]     From the teachings herein persons skilled in the art will appreciate that the inventive files may by manufactured by using or adapting file manufacturing techniques. For example, grinding methods and machinery are disclosed in U.S. Pat. No. 5,464,362 (Heath et al.). An abrasive grinding wheel is used to remove the desired amount of material from the alloy wire stock and produces the desired cross-sectional flute shape as described in U.S. Pat. No. 5,464,362. Other manufacturing techniques, such as chemical milling and torsioning, which may be used to create certain geometries, are disclosed in U.S. Pat. No. 6,968,619, which is hereby incorporated by reference as if recited in full herein for all purposes.  
         [0050]     Persons skilled in the art will recognize that many modifications and variations are possible in the details, materials, and arrangements of the parts and actions which have been described and illustrated in order to explain the nature of this invention and that such modifications and variations do not depart from the spirit and scope of the teachings and claims contained therein.