JP 2006-149675 A 6.15. 2006
`
`(19) Japan Patent Office (JP)
`
`(51) Int. Cl.
` A61C 5/02
`
`
`
`
`(01.2006)
`
`
`
`
`(12) Japanese Unexamined Patent
`Application Publication (A)
`
`
`(11) Japanese Unexamined Patent
`Application Publication Number
`2006-149675
`(P2006-149675A)
`(43) Publication date: June 15, 2006 (6.15. 2006)
`
`FI
` A61C 5/02
`
`
`Theme codes (reference)
`
` 4CO52
`
`
`Request for examination: Not yet requested Number of claims: 1 OL (Total of 11 pages)
`
`(21) Application number
`
`(22) Date of application
`
`Japanese Patent
`Application
`2004-344717
`(P2004-344717)
`November 29, 2004
`(11.29.2004)
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`(71) Applicant
`
`(74) Agent
`
`(74) Agent
`
`(72) Inventor
`
`(72) Inventor
`
`
`
`390003229
`Mani K.K.
`8-3 Kiyohara Kogyo Danchi, Utsunomiya-shi,
`Tochigi-ken
`100066784
`Patent Attorney Shukichi NAKAGAWA
`100095315
`Patent Attorney Hiroyuki NAKAGAWA
`Kanji MATSUTANI
`c/o Mani K.K.
`743 Oaza Naka Akutsu, Takanezawa-machi,
`Shioya-gun, Tochigi-ken
`Kaoru OKANE
`c/o Mani K.K.
`743 Oaza Naka Akutsu, Takanezawa-machi,
`Shioya-gun, Tochigi-ken
`
`
`
`Continued on the last page
`
`
`(54) (TITLE OF THE INVENTION) Root canal treatment apparatus
`
`(57) (ABSTRACT)
`(PROBLEM) Provide a highly durable root canal treatment
`apparatus that is unlikely to become damaged in the event
`that flex acts upon it while rotating during root canal
`formation.
`(MEANS FOR SOLVING) Work portion 4 of a designated
`length from tip 3 is formed on file A serving as the root
`canal treatment apparatus, which has a shaft-shaped needle
`portion 1 made of nickel-titanium alloy on which a shank 5
`is formed continuously with work portion 4, and at least a
`portion or the entirety of work portion 4 is subjected to heat
`treatment focused on resistance to rotating fatigue.
`(SELECTED DRAWING) Fig. 1
`
`
`
`
`
`1 of 12
`
`IPR2015-00632 - Ex. 1027
`US ENDODONTICS, LLC., Petitioner
`
`

`

`(2)
`
`JP 2006-149675 A 6.15. 2006
`
`(SCOPE OF PATENT CLAIMS)
`(CLAIM 1) Shaft-shaped root canal treatment apparatus made of nickel-titanium alloy, on which a work portion of a designated
`length from the tip is formed and on which a shank is formed continuously with said work portion, which root canal treatment
`apparatus is characterized in that at least a portion or the entirety of the work portion is subjected to heat treatment focused on
`resistance to rotating fatigue.
`(DETAILED DESCRIPTION OF THE INVENTION)
`(TECHNICAL FIELD)
`(0001)
` This invention relates to a root canal treatment apparatus for dental care, particularly to a root canal treatment apparatus that
`has improved resistance to wear arising from rotation of a root canal treatment apparatus that performs the intended treatment by
`rotating, entering and exiting in the length direction, or repeatedly switching between forward and reverse by roughly 1/4 of a
`rotation.
`(BACKGROUND ART)
`(0002)
` Examples of apparatuses for the treatment of the root canal of a tooth by rotation that shape the root canal by cutting include a
`file and a reamer. These root canal treatment apparatuses are comprised of a member shaped by forming a work portion provided
`with a cutting edge or projection on a finely tapered axial rod in accordance with the treatment objective, or forming a work
`portion by shaping a tapered axial rod into a spiral shape. Furthermore, depending on the model, a handle or grip allowing the
`doctor to grasp and operate the apparatus may be integrally attached to the end of the aforesaid member to allow the doctor to
`directly operate the apparatus or grip the apparatus by means of the chuck of a handpiece or the like.
`(0003)
` Root canals are very fine and there is considerable disparity in their shape and thickness from person to person. For this reason,
`even the same model of root canal treatment apparatus comes in a variety of models of differing thickness. For example, if using
`a file to form the root canal by cutting, it is necessary to deform the file according to the shape of the root canal in order to keep
`from damaging the tissue surrounding the root canal, i.e. it is necessary for the file to have appropriate elasticity.
`(0004)
` The technology in Patent Literature 1 has been proposed as a root canal treatment apparatus with high elasticity and shape
`restorability of the kind described above. This technology relates to a root canal treatment apparatus manufactured by forming a
`work portion on shape memory-treated axial rod material having superelastic property by performing removal processing while
`retaining at below the shape memory treatment temperature.
`(0005)
`
`In the aforesaid root canal treatment apparatus, the axial rod on which a work portion has been formed deforms supply
`according to applied external force and rapidly regains its original shape when the external force is removed. For this reason, it is
`able to follow the shape of the root canal very closely, making it possible to form a root canal to a high level of precision.
`(0006)
`(PATENT LITERATURE 1) Japanese Patent Publication No. 3375765
`(DISCLOSURE OF THE INVENTION)
`(PROBLEM TO BE SOLVED BY THE INVENTION)
`(0007)
`
`In the root canal treatment apparatus in the aforesaid Patent Literature 1, the entire length of the work portion has uniform
`superelastic property, for which reason when the work portion is bent, the work portion on the free end attempts to return to its
`original shape, producing stress as the tip is inserted into the root canal and bent during root canal treatment. In particular, when
`shaping the root canal, because rotation occurs with primarily the tip of the work portion bent, flex stress acts on the work portion,
`producing an issue whereby there is a higher likelihood of damaging the narrow tip portion.
`(0008)
` The objective of this invention is to provide a root canal treatment apparatus that is unlikely to become damaged in the event
`that flex acts upon it while rotating during root canal formation, i.e. that is highly durable.
`(MEANS OF SOLVING THE PROBLEM)
`(0009)
`
`
`
`2 of 12
`
`IPR2015-00632 - Ex. 1027
`US ENDODONTICS, LLC., Petitioner
`
`

`

`(3)
`
`JP 2006-149675 A 6.15. 2006
`
` To solve the aforesaid problem, the root canal treatment apparatus in this invention is a shaft-shaped root canal treatment
`apparatus made of nickel-titanium alloy, on which a work portion of a designated length from the tip is formed and on which a
`shank is formed continuously with said work portion, in which root canal treatment apparatus at least a portion or the entirety of
`the work portion is subjected to heat treatment focused on resistance to rotating fatigue.
`(EFFECT OF THE INVENTION)
`(0010)
`
`In the root canal treatment apparatus in this invention, subjecting at least a portion or the entirety of the work portion to heat
`treatment focused on resistance to rotating fatigue makes it possible to achieve high resistance to flex occurring as a result of
`rotation during root canal treatment.
`(PREFERRED EMBODIMENT OF THE INVENTION)
`(0011)
` The root canal treatment apparatus in this invention is an apparatus for the treatment of a root canal by rotation, and applies to
`all apparatuses made using axial-shaped material made of nickel-titanium (Ni-Ti) alloy. In root canal treatment apparatuses of
`this kind, a work portion having a shape most suited to the intended treatment is formed on one end, and an operation portion
`operated by the doctor is formed on the other end. This operating portion is formed into a handle if directly operated by hand by
`the doctor, or is furnished with a handle in a shape most suited to the structure of the grip of said apparatus in the event that an
`apparatus such as a handpiece is used.
`(0012)
`
`In particular, subjecting at least a portion or the entirety of the work portion to heat treatment focused on resistance improves
`the durability of the site on which flex acts during root canal treatment, making it possible to eliminate the risk of breakage.
`(EMBODIMENT 1)
`(0013)
` Preferred embodiments of the root canal treatment apparatus in this invention will be described below using the drawings. Fig.
`1 is a drawing showing a file that is a representative example of a root canal treatment apparatus. Fig. 2 is a schematic drawing
`illustrating the composition when performing a fatigue rupture test for the tip of the file.
`(0014)
` The shape of file A will be described by means of Fig. 1 to represent the aforesaid root canal treatment apparatus. File A is an
`apparatus that cuts the wall of the root canal, and is comprised of a needle 1 and handle 2.
`(0015)
` A tapered work portion 4 is formed on needle 1 over a span of a designated length from tip 3, and a straight shank 5 is formed
`continuously with work portion 4. Work portion 4 can have a rectangular, triangular or square shape depending on the type, each
`of which is constituted in such a way as to be able to exert its own unique functions.
`(0016)
`
`In File A in this embodiment, forming the rectangular cross-section into a spiral shape along work portion 4 produces a groove
`4a and cutting edge 4b along said groove 4a.
`(0017)
` Shank 5 has the function of being attached to handle 2. As indicated in Fig. 2, a handle can be constituted in such a way as to
`be gripped by the chuck of a handpiece or allow a doctor to grip it while operating the apparatus, with each formed into a shape
`and from a material corresponding to its function.
`(0018)
` For example, the handle 2 shown in the drawing is made of a metal such as stainless steel, and shank 5 is inserted into a hole
`formed in the axis and fastened by bonding. If forming a handle operated by having a doctor grip it by hand, shank 5 is
`sometimes fastened by integrally insert-molding by injection-molding with a synthetic resin.
`(0019)
` Needle 1 is made of nickel-titanium (Ni-Ti) alloy and is formed using a wire having a diameter corresponding to the diameter
`
`
`
`
`3 of 12
`
`IPR2015-00632 - Ex. 1027
`US ENDODONTICS, LLC., Petitioner
`
`

`

`(4)
`
`JP 2006-149675 A 6.15. 2006
`
`of needle 1 comprising file A, with portion 6, which is a portion of work portion 4, being subjected to heat treatment focused on
`resistance to rotating fatigue (hereinafter referred to as “durability heat treatment”).
`(0020)
` Moreover, in this embodiment, durability heat treatment of file A is performed only on portion 6 from tip 3 of work portion 4,
`but naturally, it is also acceptable to perform durability heat treatment over the entirety of work portion 4 in this invention.
`(0021)
` There is no particular restriction on the length of portion 6 of work portion 4. In tests of this invention and the like, there were
`many instances of breakage at the region 2 mm to 3 mm from the tip when the entirety of the work portion was made to have
`superelastic property. For this reason, the length of portion 6 of work portion 4 must be at least 2 mm from tip 3, and at most the
`full length of work portion 4. The range for the preferable length of portion 6 is on the order of 3 mm to 10 mm from tip 3 when
`the length of work portion 4 is 16 mm, 3 mm or 4 mm being particularly preferable.
`(0022)
` Furthermore, the length of portion 6 may be altered to correspond to the taper of file A. For example, if the taper is 2/100, the
`portion furthest from tip 3 of work portion 4 (base) will not have a large diameter, so by using a designated length range from tip
`3 for portion 6 and giving the other portions superelastic property, it is possible to retain the strength of the base. If the taper is
`4/100 or 6/100, the diameter of the base is large, so the strength of the base will be retained even if the entirety of work portion 4
`is subjected to durability heat treatment, and operability will be good.
`(0023)
` Durability heat treatment of portion 6 of work portion 4 is performed by heating the portion intended for durability heat
`treatment (portion 6 or the entirety of work portion 4) to a temperature obtained by testing to be described below, and retaining
`the raised temperature for a length of time obtained by testing. This durability heat treatment sets the Af temperature of the Ni-Ti
`alloy serving as the material of the file to a temperature greater than normal temperature, thereby making the site of portion 6
`able to exert shape memory function.
`(0024)
`
`In a file A comprised in the manner set forth above, prior to treatment, a doctor is able to pre-curve portion 6 in accordance
`with the shape of the root canal or the shape of the apical foramen. By thus performing pre-curving, it becomes possible for tip 3
`and portion 6 to closely follow the root canal when tip 3 is inserted into the root canal while performing treatment. Subsequent to
`completion of treatment and removal from the root canal, the doctor can apply force to cause it to regain its original shape, or
`heating can be performed to a temperature greater than the Af temperature set by durability heat treatment to cause it to regain its
`original shape.
`(0025)
` The aforesaid portion 6 is extremely flexible, which makes it possible to extend the length of time until breakage when work
`portion 4 is rotated while bent while tip 3 is inserted into the root canal, or when entering and exiting in the length direction, or
`when repeatedly switching between forward and reverse by roughly 1/4 of a rotation.
`(0026)
`
`In particular, because work portion 4 is formed in a tapered shape, when work portion 4 is bent with tip 3 as the fulcrum, shank
`5 will remain essentially straight, making shank 5 of work portion 4 an arc shape with a small curvature, while the curvature
`increases moving towards portion 6 such that the arc becomes more prominently curved, and portion 6 will be significantly bent.
`In short, work portion 4 is not bent uniformly, but is rather bent in accordance with the taper. When the bending of work portion
`4 is released, sections other than portion 6 return to their original shape (for example straight) and portion 6 retains its bent shape.
`(0027)
` Next, the testing method for setting the heat treatment temperature and retention time (heat treatment conditions) when
`performing heat treatment focused on resistance to rotating fatigue over either portion 6, which is a portion of work portion 4, or
`the entirety of work portion 4, will be described together with results thereof.
`
`
`
`4 of 12
`
`IPR2015-00632 - Ex. 1027
`US ENDODONTICS, LLC., Petitioner
`
`

`

`(5)
`
`JP 2006-149675 A 6.15. 2006
`
`(0028)
` The objective of this testing is to investigate the heat treatment conditions most conducive to achieving high durability in file A,
`assuming the most extreme rotation during root canal treatment involving rotating, entering and exiting in the length direction or
`repeatedly switching between forward and reverse by roughly 1/4 of a rotation, as well as to investigate the heat treatment
`conditions common to different Ni-Ti alloys.
`(0029)
` For this reason, this testing was performed by producing files A with the same specifications using as raw material a plurality
`of types of Ni-Ti alloy wire, performing fatigue rupture test on a plurality of samples subjected to heat treatment under different
`temperature and retention times using the device shown in Fig. 2, measuring the time until rupture, and comparing the measured
`results, thereby discovering the heat treatment conditions focused on durability to rotating fatigue.
`(0030)
`
`It is best for the time until occurrence of fatigue rupture in file A to be as long as possible. However, because there must be
`some benchmark in order to make a judgment, in this test, the benchmark was set to roughly 20 minutes without the occurrence
`of fatigue rupture when tested with the fatigue rupture tester described below.
`(0031)
` Using a wire with a diameter of roughly 1.0 mm composed of Ni: 55.76 wt%, remainder Ti (material 1), Ni: 55.91 wt%,
`remainder Ti (material 2), Ni: 55.97 wt%, remainder Ti (material 3), Ni: 55.90 wt%, remainder Ti (material 4) and Ni: 55.89 wt%,
`remainder Ti (material 5) as the material comprising file A, a plurality of no. 30 files were produced, each having a tip diameter
`of roughly 0.3 mm, taper 4/100, rectangular cross-sectional shape, roughly 25 mm length of needle projecting from handle 2 and
`roughly 15 mm length of work portion.
`(0032)
` Next, samples were produced from the files A produced from materials 1 to 5, one not subjected to heat treatment (untreated),
`one heat treated by retaining at 300°C for 30 minutes (heat treatment condition 1), one heat treated by retaining at 400°C for 30
`minutes (heat treatment condition 2), one heat treated by retaining at 500°C for 30 minutes (heat treatment condition 3), and one
`heat treated by retaining at 600°C for 15 minutes (heat treatment condition 4), and a fatigue rupture test (durability) was
`performed, with a bending test and torsion test performed corroboratively.
`(0033)
` Moreover, during each test, in one sample, heat treatment was performed by inserting the needle 1 made of Ni-Ti alloy into an
`electric furnace and subjecting the entirety of work portion 4 to heat treatment, while in another sample, heat treatment was
`performed only for portion 6 from tip 3. Five samples were tested under the same conditions. Indicated values are a summary of
`test data.
`(0034)
` First, the bending test method and results will be described. The bending test was performed using a sample in which the
`entirety of needle 1 was heat treated, by bending to 45° while grasping a location 3 mm from the tip 3 of work portion 4 and
`measuring the maximum torque. The results of the bending test for untreated samples 1 to 5 were within the range of 40gf-cm to
`50gf-cm, for heat treatment condition 1 samples 1 to 5 within the range of 40gf-cm to 55gf-cm, for heat treatment condition 2
`samples 1 to 5 within the range of 35gf-cm to 40gf-cm, for heat treatment condition 3 samples 1 to 5 within the range of 30gf-cm
`to 40gf-cm, and for heat treatment condition 4 samples 1 to 5 within the range of 35gf-cm to 40gf-cm, showing no significant
`difference.
`(0035)
` Next, the torsion test method and results will be described. The torsion test was performed using a sample in which the entirety
`of needle 1 was heat treated, by grasping a location 3 mm from the tip 3 of work portion 4 and rotating, and measuring the
`maximum torque and angle at the time of rupture. The results of the torsion test for the untreated condition samples 1 to 5 were
`within the range of maximum torque 70gf-cm to 80gf-cm and angle 400° to 500°, for heat treatment condition 1 samples 1 to 5
`
`
`
`
`5 of 12
`
`IPR2015-00632 - Ex. 1027
`US ENDODONTICS, LLC., Petitioner
`
`

`

`(6)
`
`JP 2006-149675 A 6.15. 2006
`
`within the range of maximum torque 70gf-cm to 80gf-cm and angle 400° to 500°, for heat treatment condition 2 samples 1 to 5
`within the range of maximum torque 80gf-cm to 120gf-cm and angle 400° to 600°, for heat treatment condition 3 samples 1 to 5
`within the range of maximum torque 70gf-cm to 100gf-cm and angle 450° to 700°, and for heat treatment condition 4 samples 1
`to 5 within the range of maximum torque 70gf-cm to 90gf-cm and angle 800° to 1100°, revealing that although the test results for
`heat treatment condition 4 were significant compared to the other conditions, there was no significant difference between the
`other heat treatment conditions.
`(0036)
` Next, the fatigue rupture test method and results will be described. The fatigue rupture test was performed using a sample in
`which the entirety of needle 1 was heat treated using the device shown in Fig. 2. In short, using a device furnished with a pair of
`pins 21, 22 having a groove 21a, 22a capable of receiving the tip 3 of work portion 4, one of the pins 21 was set in such a way
`that the center thereof corresponded to a position 4 mm from the tip 3 of work portion 4 and tip 3 was inserted into the groove
`22a of the other pin 22, thereby bending portion 6 of work portion 4 by roughly 45 degrees, this state was maintained while
`rotating 200 times per minute, and time until rupture was measured.
`(0037)
` The results of this fatigue rupture test revealed that time until fatigue rupture changes significantly depending on heat treatment
`conditions. In short, time until fatigue rupture was roughly 18 minutes in material 2, which had the highest durability among the
`untreated condition, within the range of 5 to 10 minutes in the case of heat treatment condition 1, within the range of 4 to 11
`minutes in the case of heat treatment condition 3, and within the range of 3 to 5 minutes in the case of heat treatment condition 4,
`whereas time until fatigue rupture was within the range of 8 to 56 minutes in the case of heat treatment condition 2 (400°C – 30
`minutes), revealing a significant increase in the time until fatigue rupture compared to the other heat treatment conditions.
`(0038)
`
`In short, when heat treatment is performed under heat treatment condition 2, there is significant lengthening effect on the
`fatigue rupture time, indicating that this heat treatment is capable of imparting a high level of durability.
`(0039)
` As indicated above, it was found that performing heat treatment of Ni-Ti alloy material while retaining for 30 minutes at
`400°C improved durability. However, it is not clear whether or not the condition of 400°C – 30 minutes is ideal. For this reason,
`a fatigue rupture test was performed by using a single material and processing time and changing the temperature.
`(0040)
` The material used in the test was the aforesaid material 2 having a composition of Ni: 55.91 wt%, remainder Ti. A fatigue
`rupture test was performed for samples heat treated, respectively, at a temperature of 250°C, 300°C, 350°C, 375°C, 400°C,
`410°C, 420°C, 425°C, 430°C, 440°C, 450°C, 475°C, 500°C and 550°C.
`(0041)
` The results of the aforesaid rupture tests are shown in Fig. 3. As shown in this diagram, results show that time until fatigue
`rupture exceeds 15 minutes when heat treatment temperature is within the range of 400°C to 450°C and exceeds 20 minutes when
`heat treatment temperature is within the range of 430°C to 440°C. Based on these test results, it can be said that heat treatment
`focused on resistance to rotating fatigue can be performed over the entirety of the work portion by performing heat treatment at a
`heat treatment temperature within the range of 400°C to 450°C and retaining for 30 minutes.
`(0042)
` Next, using a partial heating device not shown in the drawings[,] with the heat treatment range within the range of roughly 5
`mm from tip 3 of work portion 4 or within the range of roughly 10 mm from tip 3, the aforesaid material 2 composed of Ni: 55.91
`wt%, remainder Ti as the material, 400°C (350°C, 340°C), 425°C (370°C, 360°C), 450°C (390°C, 375°C), 475°C (410°C,
`390°C), 500°C (440°C, 420°C), 525°C (460°C, 430°C), 550°C (480°C, 440[°C]) as the heat treatment temperature – partial
`heating device temperature setting, and 45 minutes (fixed) as the retention time, a fatigue rupture test was performed on a sample
`subjected to heat treatment at a temperature selected from among the aforesaid conditions. As a comparative example, a fatigue
`rupture test was performed on a sample that was heat-treated at 400°C for 45 minutes using a drier.
`
`
`
`6 of 12
`
`IPR2015-00632 - Ex. 1027
`US ENDODONTICS, LLC., Petitioner
`
`

`

`(7)
`
`JP 2006-149675 A 6.15. 2006
`
`(0043)
` Moreover, heat treatment of a range roughly 5 mm and roughly 10 mm from the tip of work portion 4 was performed on a very
`fine axial bolt within a limited range, so it is not possible to prescribe clear dimensions. For this reason, it is difficult to express
`the length range from tip 3 as a precise numeral value, and hence the range must be expressed as a range of on the order of
`roughly 5 mm or roughly 10 mm.
`(0044)
` When performing heat treatment using partial heating device, there is no guarantee that the temperature setting of the partial
`heating device and the actual temperature of the sample will match precisely. When heat treatment was actually performed with a
`partial heating device, a difference was found between the measured surface temperature of the sample and the temperature
`setting. In short, the first temperature in parentheses is the surface temperature of the sample as measured when a range of
`roughly 5 mm from the tip was heated, and the second temperature is the surface temperature of the sample as measured when a
`range of roughly 10 mm from the tip was heated, versus the aforesaid temperature setting of the partial heating device. Thus, the
`surface temperature of the sample during heat treatment was measured to be a temperature lower than the temperature setting of
`the partial heating device.
`(0045)
` As a result of the aforesaid tests, it was found that in the case of a heat treatment range of roughly 5 mm, the time until
`occurrence of fatigue rupture was roughly 29 minutes when the heat treatment temperature was set to 425°C, whereas in the case
`of other heat treatment conditions fatigue rupture occurred after 20 minutes or less.
`(0046)
`
`In the case of a heat treatment range of roughly 10 mm, the time until occurrence of fatigue rupture exceeded 20 minutes when
`the heat treatment temperature was within a range of 425°C to 500°C. In the case of a heat treatment temperature of 525°C,
`fatigue rupture occurred at roughly 19 minutes.
`(0047)
`
`In the comparative example, the time until occurrence of fatigue rupture was roughly 35 minutes.
`(0048)
` For practical purposes, it is adequate for the time until occurrence of fatigue rupture to be on the order of roughly 20 minutes
`or greater, for which reason it can be said that heat treatment focused on resistance to rotating fatigue over a portion of the work
`portion can be applied by performing heat treatment under heat treatment conditions of 425°C – 45 minutes in a file A that was
`heat-treated within a range of roughly 5 mm from the tip, and under heat treatment conditions of 425°C – 45 minutes to 525°C –
`45 minutes in a file A that was heat-treated within a range of roughly 10 mm from the tip.
`(0049)
` As set forth above, putting together the results of fatigue rupture tests of samples wherein the entirety of the work portion 4
`was heat-treated and fatigue rupture [tests] of samples in which a range of 5 mm and 10 mm from the tip of the work portion was
`heat-treated, it can be said to be possible to apply heat treatment focused on resistance to rotating fatigue over a portion or the
`entirety of the work portion by performing heat treatment with the heat treatment temperature set to within the range of 400°C to
`450°C and retaining for 30 minutes to 45 minutes.
`(0050)
`
`In a file A of the kind described above, by gripping handle 2 in the chuck of a handpiece not shown in the drawings and having
`the doctor hold this handpiece, once portion 6 formed on work portion 4 has been pre-bent into a shape corresponding to the
`shape of the root canal of the patient, it is possible to shape the root canal by cutting the walls of said root canal by inserting tip 3
`into the root canal and rotating in the direction of cutting edge 4b while displacing axially.
`(0051)
` Moreover, although in this embodiment a cutting edge 4b was formed because a file A was taken as an example of the root
`canal treatment apparatus, a cutting edge 4b will not necessarily be formed in the work portion 4 of all root canal treatment
`apparatuses; in some cases, a pointed projection or tapered coil will be formed. Even in the case of root canal treatment
`apparatuses of this kind, it is possible to achieve high durability by performing heat durability heat treatment over portion 6 of
`work portion 4 or over the entirety of work portion 4 as long as the root canal treatment apparatus treats a root canal by rotation.
`(0052)
` As set forth above, there is no particular restriction on the method of manufacturing a file A; however, representative methods
`will be described briefly. The first manufacturing method involves forming a work portion by performing metal removal
`
`
`
`
`7 of 12
`
`IPR2015-00632 - Ex. 1027
`US ENDODONTICS, LLC., Petitioner
`
`

`

`(8)
`
`JP 2006-149675 A 6.15. 2006
`
`processing on material previously granted superelasticity, and subsequently subjecting a portion or the entirety of the tip of the
`work portion to durability heat treatment.
`(0053)
`
`In short, axial bolt-shaped material is formed by cutting wire made of Ni-Ti alloy granted superelasticity in advance and
`having a diameter corresponding to the thickness of the intended file to the length of said file, and then a needle portion is formed
`by tapering this material, machining the groove and cutting edge, machining the tip, and machining the work portion and shank.
`At this time, because it is impossible to perform plastic working on the material due to its superelasticity, the various processes
`performed on the material are performed by means of processes involving the removal of metal including grinding.
`(0054)
` Next, a portion subjected to durability heat treatment is formed over a range of a designated length from the tip of the work
`portion or over the entirety of work portion 4. This process is performed by using refrigerant to cool the sections of the needle
`already formed into a prescribed shape that do not correspond to the sections intended to be subjected to durability heat treatment,
`and then heating according to pre-set heat treatment conditions for temperature and retention time. There is no particular
`restriction on the refrigerant used at this time; for example, water can be used.
`(0055)
` The intended file can then be manufactured by inserting the shank of the needle provided with a portion 6 subjected to
`durability heat treatment over a range of a designated length from the tip of the work portion or over the entirety of the work
`portion in the manner set forth above into the handle and bonding the two together.
`(0056)
` A second manufacturing method involves manufacturing the intended file by subjecting a range of a designated length
`corresponding to the portion subjected to durability heat treatment, or a portion corresponding to the entirety of the work portion,
`to durability heat treatment from one end at the stage where the material is formed, and subsequently performing processing
`involving the removal of metal from the material to form a work portion with a groove and cutting edge.
`(0057)
`
`In the second manufacturing method described above, a segment subjected to durability heat treatment at the material stage
`and a section having superelasticity are formed, with the work portion being formed by subjecting this material to metal removal
`processing. Accordingly, a needle shape is remembered by, and a groove and cutting edge continuous with the superelastic
`portion are formed on, the portion subjected to durability heat treatment.
`(0058)
` The intended file can then be manufactured by subjecting material furnished in the manner set forth above with a segment
`corresponding to the portion subjected to durability heat treatment and a segment corresponding to the superelastic portion to
`processing involving metal removal so as to form a needle comprised of a work portion and shank, and subsequently inserting the
`shank in the handle and bonding the two together.
`(INDUSTRIAL APPLICABILITY)
`(0059)
` The root canal treatment apparatus in this invention proffers the advantage of making it possible to prolong the length of time
`until occurrence of rupture when treating a root canal by inserting the tip portion thereof into a root canal with a complicated
`shape and rotating, even when fatigue occurs as a result of this rotation.
`(BRIEF DESCRIPTION OF THE DRAWINGS)
`(0060)
`(FIG. 1) Drawing showing a file serving as a representative example of a root canal treatment apparatus.
`(FIG. 2) Schematic drawing illustrating the composition when performing a fatigue rupture test for the tip of the file.
`(FIG. 3) Diagram showing the test results for fatigue rupture time when the same material was heat-treated at a different
`temperature.
`(EXPLANATION OF REFERENCES)
`(0061)
`A
`1
`2
`
`File
`Needle
`Handle
`
`
`
`
`
`
`
`8 of 12
`
`IPR2015-00632 - Ex. 1027
`US ENDODONTICS, LLC., Petitioner
`
`

`

`(9)
`
`JP 2006-149675 A 6.15. 2006
`
`Tip
`Work portion
`Groove
`Cutting edge
`Shank
`Portion
`Pin
`Groove
`
`
`
`
`
`
`
`
`
` (Fig. 2)
`
`
`3
`
`4
`
`4a
`
`4b
`
`5
`
`6
`
`21, 211
`21a, 22a
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`(Fig. 1)
`
`
`
`
`
`
`
`9 of