ENDODONTIC TOOL
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] The present application is based on, claims priority to, and incorporates herein by reference in its entirety United States Provisional Patent Application 62/487,363, filed April 19, 2017, entitled "Endodontic Tool".
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
[0002] Not Applicable.
BACKGROUND OF THE INVENTION
1 . Field of the Invention
[0003] The current invention relates to systems and methods of endodontic tools, specifically endodontic tools having superelastic properties for removal of broken instruments and debris.
2. Description of the Related Art
[0004] Instrument fracture is a recurring issue during root canal preparation procedures. A broken instrument can be problematic for a clinician who can attempt to remove the broken instrument, or leave the broken instrument in place and bypass the broken instrument while continuing the procedure.
[0005] The consequences of leaving and/or bypassing broken instruments can be serious. In some cases, leaving a broken instrument in the tooth can necessitate future extraction of the tooth which results in a loss of any benefit obtained from performing the root canal procedure.
[0006] Accordingly, removal of the broken instrument from the tooth is preferred to prevent additional problems in the future. Retrieving broken instruments pose formidable challenges to clinicians. In particular, common broken instruments are files, drills, bores, burrs, or other cutting instruments that break due to becoming wedged inside the structure of the tooth. A common cause for fracture of an instrument is the wedging of an instrument in the structure of a tooth, leading it to be difficult to remove or pull the instrument free. Further, the instrument would often break at a point not easily visible or accessible to the clinician as a drill or similar instrument could break at a point within its own hole and therefore cannot be accessed by an instrument larger than itself without boring out additional space.
[0007] Therefore, there exists a need for an endodontic tool for removal of broken instruments and debris wherein at least a portion of the tool has superelastic properties.
SUMMARY OF THE INVENTION
[0008] The present invention relates to an endodontic tool for removal of broken instruments and debris wherein at least a portion of the tool has superelastic properties.
[0009] In some embodiments, an endodontic tool is provided. The endodontic tool can comprise a shank and a collar. The shank can have a proximal end and a distal end, and can comprise a nickel-titanium alloy. The collar can have a first portion and a second portion. The first portion of the collar can be configured to receive a proximal end of the shank. The second portion of the collar can have an opening dimensioned to engage a distal end of a dental hand piece. The collar can comprise a material other than nickel titanium.
[0010] In some embodiments, the endodontic tool further can comprise a hand piece having a distal end configured to connect with the opening of the second portion of the collar.
[001 1] In some embodiments, the nickel-titanium alloy can be superelastic. In some embodiments, the collar can comprise stainless steel. The nickel-titanium alloy can be selected from nickel-titanium alloys of stoichiometric NiTi, near-equiatomic Ni- Ti, Ni-Ti-Nb alloys, Ni-Ti-Fe alloys, and Ni-Ti-Cu alloys. The nickel-titanium alloy can comprise 54-57 weight percent nickel and 43-46 weight percent titanium. The nickel- titanium alloy can consist essentially of 54-57 weight percent nickel and 43-46 weight percent titanium. The nickel titanium alloy can be superelastic at 37°C.
[0012] In some embodiments, the hand piece can be an ultrasonic hand piece or a vibratory hand piece.
[0013] In some embodiments, the collar can have a bend such that the shank is positioned at an angle with respect to an axis of the second portion of the collar.
[0014] In some embodiments, the proximal end of the shank can have an outer diameter in a range of 0.010 to 0.040 inches. The first portion of the collar can have an opening to receive the proximal end of the shank. The opening of the first portion of the collar can have an inner diameter in a range of 0.012 to 0.042 inches. The shank can be connected to the first portion of the collar via an interference fit. The shank can be connected to the first portion of the collar via a weld. The shank can be connected to the first portion of the collar via an adhesive. In some aspects, the adhesive comprises a polymeric material. In other aspects, the adhesive comprises a cross-linked epoxy resin, and the cross-linked epoxy resin can have a lap shear strength measured using ISO 4587:2003 of greater than 5 N/mm2
[0015] According to another embodiment of this disclosure, a method of manufacturing an endodontic tool is provided. The method comprises machining a shank having a proximal end and a distal end, the shank comprising a nickel-titanium alloy; molding a collar having a first portion and a second portion, the first portion of the collar being configured to receive a proximal end of the shank, the second portion of the collar having an opening dimensioned to engage a distal end of a dental hand piece, the collar comprising a material other than the nickel-titanium alloy; and securing the shank to the collar using an interference fit between the first portion of the collar and a proximal portion of the shank and using an adhesive in the first portion of the collar.
[0016] In some embodiments, the collar has a first portion and a second portion, the first portion of the collar being overmolded on a proximal end of the shank, the second portion of the collar having an opening dimensioned to engage a distal end of a dental hand piece, the collar comprising a material other than the nickel-titanium alloy. The nickel-titanium alloy can be superelastic, and the collar can comprise a machinable metal. The collar can comprise stainless steel. The nickel-titanium alloy can be selected from nickel-titanium alloys of stoichiometric NiTi, near-equiatomic Ni- Ti, Ni-Ti-Nb alloys, Ni-Ti-Fe alloys, and Ni-Ti-Cu alloys. The nickel-titanium alloy can comprise 54-57 weight percent nickel and 43-46 weight percent titanium. The nickel- titanium alloy can consist essentially of 54-57 weight percent nickel and 43-46 weight percent titanium. The nickel titanium alloy can be superelastic at 37°C.
[0017] According to another embodiment of this disclosure, a method of manufacturing an endodontic tool is provided. The method comprising machining a shank having a proximal end and a distal end, the shank comprising a nickel-titanium alloy; molding a collar having a first portion and a second portion, the first portion of the collar being configured to receive a proximal end of the shank, the second portion of the collar having an opening dimensioned to engage a distal end of a dental hand piece, the collar comprising a material other than the nickel-titanium alloy; and securing the shank to the collar using an adhesive between the first portion of the collar and a proximal portion of the shank and using an adhesive in the first portion of the collar.
[0018] In some embodiments, the adhesive can comprise a polymeric material. The adhesive can comprise a cross-linked epoxy resin. The cross-linked epoxy resin can have a lap shear strength measured using ISO 4587:2003 of greater than 5 N/mm2.
[0019] In some embodiments, an endodontic tool is provided. The endodontic tool can comprise an ultrasonic tip that can have a stainless steel or other machinable metal portion that can connect via threads or other fasteners to an ultrasonic generation unit. The ultrasonic tip can have a nickel-titanium or other flexible metal/alloy that can allow the distal portion of tip to have flexibility. The two metals can form one solid ultrasonic tip via bonding, welding, molding, adhesive, or mechanical interface. The flexible distal end of tip may or may not be tapered, but point of distal end can have a taper.
[0020] These and other features, aspects, and advantages of the present invention will become better understood upon consideration of the following detailed description, drawings, and appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 is a perspective view of an endodontic tool according to one embodiment of this disclosure.
[0022] Figure 2 is a right side view of the endodontic tool of Figure 1 . [0023] Figure 3 is a left side view of the endodontic tool of Figure 1 .
[0024] Figure 4 is a cross-sectional view taken along the line 4-4 of Figure 3.
[0025] Figure 5 is a rear view of the endodontic tool of Figure 1.
[0026] Figure 6 is a cross-sectional view taken along the line 6-6 of Figure 5.
[0027] Figure 7 is a bottom view of the endodontic tool of Figure 1 .
[0028] Like reference numerals will be used to refer to like parts from Figure to
Figure in the following description of the drawings.
DETAILED DESCRIPTION OF THE INVENTION
[0029] Certain exemplary embodiments will now be described to provide an overall understanding of the principles of the structure, function, manufacture, and use of the devices and methods disclosed herein. One or more examples of these embodiments are illustrated in the accompanying drawings. Those skilled in the art will understand that the devices and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments and that the scope of the present invention is defined by the claims. The features illustrated or described in connection with one exemplary embodiment may be combined with the features of other embodiments. Such modifications and variations are intended to be included within the scope of the present invention.
[0030] Figures 1 -7 show an exemplary embodiment of an endodontic tool 20 according to this disclosure. The endodontic tool 20 can be configured to perform a variety of endodontic tasks, including but not limited to, extraction of an instrument or debris from a tooth of a subject. In some embodiments, endodontic tool 20 can be used during a root canal procedure. The endodontic tool 20 can include a shank 24 and a collar 28 that can be connected to a separate hand piece.
[0031] The shank 24 can be generally conical in shape and can extend outwardly away from the collar 28. The conical shape of the shank 24 may create a tapered shape from a proximal end 30 of the shank to a distal end 32 of the shank, the proximal end 30 having a larger outer diameter than the distal end 32 having a flat end surface 34. The flat end surface 34 can be closed such that the shank 24 is a solid conical piece of material. Although a flat end surface 34 is shown, the distal end 32 can form any appropriate shape such as a pointed end or a hemispherical end. The proximal end 30 of the shank 24 can be machined to be any appropriate size to connect with the collar 28. In some embodiments, the outer diameter of the proximal end 30 of the shank 24 can be between 0.010"-0.040". In some embodiments, the outer diameter of the proximal end 30 of the shank 24 can be between 0.015"-0.030". In other embodiments, the preferred outer diameter of the proximal end 30 of the shank 24 is 0.018". As used herein, the term machined, or machinable refers to a material, object, device, or system that is able to be worked by a machine tool such as a lathe, grinder, or milling machine.
[0032] As shown, the shank 24 extends linearly away from the collar 28. In other embodiments, the shank 24 can form different shapes. One non-limiting example can be a gooseneck-shaped shank where a proximal end of the shank forms an initial posterior curve followed by an anterior curve allowing the shank to extend anteriorly outward to the distal end.
[0033] The shank 24 can comprise a nickel titanium alloy. An example nickel- titanium alloy includes 54-57 weight percent nickel and 43-46 weight percent titanium. Preferably, the titanium alloy used for the shank 24 includes 54-57 weight percent nickel and 43-46 weight percent titanium and is commercially available as Nitinol 55. Thus, most preferably, the shank 24 consists essentially of 54-57 weight percent nickel and 43-46 weight percent titanium thereby avoiding the inclusion of elements that affect the properties of the alloy. The nickel titanium alloy may also be selected from nickel-titanium alloys of stoichiometric NiTi, near-equiatomic Ni-Ti, Ni- Ti-Nb alloys, Ni-Ti-Fe alloys, Ni-Ti-Cu alloys, and other small percentage of trace metals.
[0034] The proximal end 30 of the shank 24 is dimensioned to be received in an opening 38 in a distal end 40 of a first portion 42 of the collar 28. An inner diameter of the opening 38 in the distal end 40 of the first portion 42 of the collar 28 may be dimensioned to be slightly larger than the outer diameter of the proximal end 30 of the shank 24. In some embodiments, an inner diameter of the opening 38 in the distal end 40 of the first portion 42 of the collar 28 can be between 0.012"-0.042". In some embodiments, an inner diameter of the opening 38 in the distal end 40 of the first portion 42 of the collar 28 can be between 0.012"-0.032". In other embodiments, the inner diameter of the opening 38 in the distal end 40 of the first portion 42 of the collar 28 can be 0.020". Accordingly, it can be desired that the inner diameter of the opening 38 in the distal end 40 of the first portion 42 of the collar 28 to be 0.002" greater than the outer diameter of the proximal end 30 of the shank 24. The outer diameter of the proximal end 30 of the shank 24 and the inner diameter of the opening 38 in the distal end 40 of the first portion 42 of the collar 28 can form an interference fit in order to secure the connection between the collar 28 and the shank 24. The interference fit may encompass a longitudinal length of 0.25 to 1 .0 inches, or 0.25 to 0.75 inches, or preferably about 0.5 inches, of the outer surface of the proximal end 30 of the shank 24.
[0035] In another embodiment, the shank 24 can be connected to the collar 28 in using any non-limiting examples of mechanical interferences to secure the shank 24 in the collar 28 as described. The connection can be any suitable connection, non- limiting examples include barbed connections, keyed connections, magnetic connections, threaded connections, etc.
[0036] The first portion 42 of the collar 28 can be positioned at a distal end 44 of the collar 28 which may feature an angular bend 46 that directs the shank 24 to protrude outward at an angle due to the angular bend 46 in the collar 28. The first portion 42 of the collar 28 can be generally cylindrical in shape and can feature an inwardly tapered portion 48 at the distal end 40 around the opening 38 in the first portion 42 of the collar 28. The inwardly tapered portion 48 can taper to meet the opening 38 to define the inner diameter of the opening 38. The shank 24 can be received in the opening 38 such that the proximal end 30 is received in the distal end 40 of the collar 28. The shank 24 can be held in the opening 38 via an interference fit between the shank 24 and the opening 38. Additionally, the shank 24 can be held in the opening 38 via a combination of an interference fit and an adhesive within the opening 38.
[0037] In other embodiments, the collar 28 may be cylindrical in shape without an angular bend. In such embodiments, the shank 24 can feature an angular bend, such as a gooseneck shape, in order to extend angularly away from the collar 28. [0038] A proximal end 50 of the first portion 42 may be positioned proximally to the angular bend 36 of the collar 28. The proximal end 50 of the first portion 42 can be connected to a distal end 52 of a second portion 54 of the collar 28. The distal end 52 of the second portion 54 can have a tapered conical shape that tapers to match an outer diameter of the proximal end 50 of the first portion 42 with an outer diameter of the distal end 52 of the second portion 54.
[0039] A proximal end 56 of the second portion 54 can be cylindrical in shape extending proximally from the tapered conical shape of the distal end 52 of the second portion 54. As shown in Figures 6-7, the proximal end 56 can have an opening 58 that can have threads 60 positioned around an inner surface of the opening 58 for connection to an external hand piece, which may be threaded to engage with the threads around the inner surface of the opening 58. In other embodiments, the connection between the second portion 54 and the hand piece can be any suitable connection (e.g. barbed, keyed, magnetic, etc.).
[0040] In some embodiments, the collar 28 may comprise a material other than a nickel-titanium alloy. In one non-limiting example, the collar 28 may be manufactured from a machinable metal, such as stainless steel. The collar 28 can be manufactured by powder injection molding, for example using stainless steel where the injection molded collar can be over-molded with the shank 24. In other embodiments, the collar 28 may be welded to the shank 24. In other embodiments, the collar 28 may be adhesively bonded to the shank 24. In some exemplary embodiments, the shank 24 can be shaped by grinding or any other suitable process.
[0041] Now that the components of the endodontic tool 20 have been described in detail, the functionality of the endodontic tool can be better appreciated. In some embodiments, the shank 24 can comprise a nickel-titanium alloy. In such embodiments, the shank 24 can be superelastic, allowing the shank 24 to exhibit elastic properties without fracturing. The superelasticity of the shank 24 can be advantageous in various applications. One non-limiting application can be the removal of a broken instrument or debris left in the tooth of a subject during a root canal procedure. The superelasticity of the shank 24 allows for improved mobility and flexibility in the tooth of the subject providing improved functionality of the endodontic tool 20 for removal of a broken instrument or debris from the tooth of a subject. The shank 24 can be superelastic when in the mouth of a subject, which can typically be at or near 37°C, thus allowing the shank 24 to return to its original shape when removed from the mouth of the subject.
[0042] The functionality of the endodontic tool 20 can be chosen by a clinician based on the hand piece that is selected. Non limiting examples of hand pieces can comprise ultrasonic, rotary, vibratory, and reciprocation hand pieces. In some embodiments, the hand piece can be an ultrasonic hand piece that can allow ultrasonic transmission through the shank 24, and the ultrasonic transmission can facilitate functionality of the shank 24 for removal of a broken instrument or debris from a root canal procedure. In such a case, the vibration can be between 22,000 Hz and 36,000 Hz, in a non-limiting example.
[0043] In some aspects, the shank 24 may have an interior chamber that extends from the proximal end 30 of the shank to the distal end 32 of the shank 24, which may have an opening at the distal end 32, for example in the flat end surface 34. The interior chamber can provide fluid communication from a fluid source through the collar 28 and into and/or through the shank 24 via the interior chamber. The introduction of an interior chamber that can receive fluid via fluid communication through the collar 28 from a fluid source can provide cooling capacity to the vibrating tip.
[0044] In some aspects, a method of manufacturing a dental tool is provided. The method can include machining a shank having a proximal end and a distal end, the shank comprising a nickel-titanium alloy. The method can also include molding a collar having a first portion and a second portion, the first portion of the collar being configured to receive a proximal end of the shank, the second portion of the collar having an opening dimensioned to engage a distal end of a dental hand piece, the collar comprising a material other than the nickel-titanium alloy. The method can also include securing the shank to the collar using an interference fit between the first portion of the collar and a proximal portion of the shank and using an adhesive in the first portion of the collar. In some aspects, the shank can be machined using a lathe, a grinder, or a milling machine. In some aspects, the collar can be molded using a metal injection molding machine, or other molding machines.
[0045] The shank may be secured to the collar using an adhesive comprising a polymeric material. Non-limiting example polymeric materials include polymers which contain epoxide groups. In an example embodiment, the shank may be secured to the collar using a polymeric adhesive comprising a cross-linked epoxy resin. Epoxy resins may be reacted (cross-linked) with themselves through catalytic homopolymerization, or with a wide range of co-reactants including polyfunctional amines, acids (and acid anhydrides), phenols, alcohols and thiols. These co-reactants are often referred to as hardeners, and the cross-linking reaction is commonly referred to as curing. In an example embodiment, the shank may be secured to the collar using a cross-linked epoxy resin formed by curing an epoxy resin with a polyglycol amine hardener. The typical properties of the cross-linked epoxy resin may be: (1 ) glass transition temperature, ASTM E 228, of 50-90°C; (2) elongation, ASTM D 638, of 5-15%; (3) tensile strength, ASTM D 638, of 25-75 N/mm2; (4) Shore hardness (cured @ 22°C for 16 to 18 hours followed by 2 hours @ 65°C), ISO 868, Durometer D: 70 to 100; and (5) lap shear strength (cured @ 22°C for 5 days, stainless steel), ISO 4587, of 1 -40 N/mm2, or 5-20 N/mm2, or greater than 5 N/mm2, or greater than 10 N/mm2. Preferably, the cross-linked epoxy resin shows excellent bond strength retention when subjected to standard sterilization methods, such as EtO and Gamma Radiation (25 to 50 kiloGrays cumulative). Preferably, the cross-linked epoxy resin maintains bond strength after 1 cycle of steam autoclave.
Example
[0046] The following Example has been presented in order to further illustrate the invention and is not intended to limit the invention in any way.
[0047] A collar (similar to collar 28 of endodontic tool 20) having an opening (similar to opening 38 of endodontic tool 20) was metal injection molded from 17-4 precipitation-hardened stainless steel. The opening had an inside diameter of 0.020". A syringe was used to fill the 0.020" opening with a two part uncured epoxy adhesive. An end of a tapered nickel-titanium shank (similar to shank 24 of endodontic tool 20) having an outside diameter of 0.018" was inserted in the opening of the collar. Syringe use helped prevent bubble formation within the small opening, providing stronger adhesion between the shank and the collar. The uncured epoxy adhesive was allowed to cure for 24 hours creating the endodontic tool.
[0048] The epoxy adhesive used in this Example was an epoxy adhesive commercially available as LOCTITE® M-31 CL Hysol medical device epoxy structural adhesive. This medical grade epoxy structural adhesive is formed by curing an epoxy resin with a polyglycol amine hardener. Typical properties of cured LOCTITE® M-31 CL Hysol medical device epoxy structural adhesive material include: (1 ) glass transition temperature, ASTM E 228, of 70°C; (2) elongation, ASTM D 638, of 8%; (3) tensile strength, ASTM D 638, of 55.2 N/mm2; (4) Shore hardness (cured @ 22°C for 16 to 18 hours followed by 2 hours @ 65°C), ISO 868, Durometer D: 80 to 90; and (5) lap shear strength (cured @ 22°C for 5 days, stainless steel), ISO 4587, of 13.6 N/mm2.
[0049] Positive feedback was obtained from clinicians who tested the product of this Example.
[0050] Thus, the invention provides systems and methods of endodontic tools, specifically endodontic tools having superelastic properties for removal of broken instruments and debris.
[0051] Although the present invention has been described in detail with reference to certain embodiments, one skilled in the art will appreciate that the present invention can be practiced by other than the described embodiments, which have been presented for purposes of illustration and not of limitation. Therefore, the scope of the appended claims should not be limited to the embodiments contained herein.