Dental tools or instruments equipped with a working part having changing mechanical properties.

Abstract

This disclosure relates to a dental tool or instrument (100) comprising a working part (110) made of a nitinol alloy. The nitinol alloy of the working part (110) is transitionable from an R-phase alloy state when heated above a transition temperature. The working part (110) is transitionable above a first transition temperature (T T1 At least a first portion (111) having a second transition temperature (T T2 It includes at least a second portion (112) having a first transition temperature (T T1 The second transition temperature (T) is lower than the working temperature, and as a result, at the working temperature, the first part (111) is in the austenite phase. T2 ) is at a temperature higher than the working temperature, so that at the working temperature the second portion (112) is in the R phase. The disclosure further relates to a method for manufacturing dental tools or instruments.

Description

[Technical Field]

[0001] This disclosure relates to a dental tool or instrument, which includes a working part intended to engage within a root canal, and which includes parts having different physical properties based on specific local mechanical properties and specific shapes. This disclosure also relates to a method for manufacturing a dental tool or instrument. [Background technology]

[0002] Related technologies The introduction of NiTi in the manufacture of dental tools and instruments has resulted in improved efficiency and quality of dental tools and instruments, as well as improved patient experience and satisfaction. In fact, dental tools and instruments made from nitinol alloys, such as Nitinol, have a low modulus of elasticity and exhibit superelasticity. The effective strain range of NiTi is much larger than that of stainless steel. Dental tools and instruments made from nitinol alloys have improved fatigue resistance.

[0003] Endodontic instruments, including files, reamers, and broaches, include a cutting section, or so-called working section, configured to receive treatment material and then form, shape, and clean the inner wall of the root canal to receive filling material, in order to eliminate any oxygen that could allow bacteria to grow in the tooth, especially near the root.

[0004] There are various factors that determine the physical properties required of such instruments. These include the desired plasticity and / or elasticity of the instrument, as well as the sharpness of the cutting edge related to the hardness and structure of the material, and specific dimensional and design limitations for different root canals.

[0005] Titanium-based alloys such as nitinol alloys and Ni / Ti materials have been introduced for use in the manufacture of endodontic instruments. For example, European Patent No. 0402293 relates to endodontic tube instruments made of titanium or titanium alloy. The use of materials such as titanium or Ni / Ti has certain advantages in terms of material flexibility. However, endodontic instruments made of such materials may have the disadvantage of lacking the necessary rigidity to provide sufficient guidance within the root canal, especially in small-diameter instruments. Furthermore, the sharpness of the cutting edge in such instruments is impaired due to the lower hardness of the material.

[0006] U.S. Patent No. 6,431,863 discloses an endodontic instrument having a working shaft portion made of a nickel-titanium alloy, wherein the shaft portion has an elastic modulus that varies along its length, resulting in the tip of the working shaft portion having higher hardness than the rest of the working shaft portion. The flexibility / rigidity of the instrument is controlled by a selected heat treatment applied to a specific region of the working shaft.

[0007] There is a need for dental tools or instruments that possess a certain degree of plasticity and elasticity, thereby enabling them to be used more efficiently. For example, endodontic instruments that can be better adapted to the longitudinal profile of the root canal. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] European Patent No. 0402293 [Patent Document 2] U.S. Patent No. 6,431,863 [Patent Document 3] International Patent Publication No. 2022IB61697 [Overview of the project]

[0009] The present disclosure relates to a dental tool or instrument comprising a working part made of a nitinol alloy. The nitinol alloy of the working part is capable of transitioning from an R-phase alloy state to an austenite-phase alloy state when heated above a transition temperature. The working part comprises at least a first part having a first transition temperature and at least a second part having a second transition temperature. The first transition temperature is a temperature lower than the working temperature of the working part, and at the working temperature, the first part is in the austenite phase. The second transition temperature is a temperature higher than the working temperature, and at the working temperature, the second part is in the R-phase.

[0010] In one embodiment, the working section is intended to engage within the root canal and extends generally along the longitudinal axis between the root apex and the shaft.

[0011] In one embodiment, the working section comprises a substantially linear apical portion with respect to the longitudinal axis and an intermediate segment extending between the apical segment and the shaft. The working section comprises a plurality of alternately arranged first portions and a plurality of second portions.

[0012] The present disclosure further relates to a method of manufacturing a dental tool or instrument.

[0013] In addition to having high resistance to fracture and repeated fatigue, the dental tools or instruments disclosed herein provide mechanical properties that vary along the length of the working part. More specifically, the dental tool or instrument has a transition temperature between the R-phase and the austenite-phase that varies along the length of the working part, and as a result, the microstructure of the nitinol also varies along the length of the working part. The dental tool or instrument has enhanced safety and performance capabilities.

Brief Description of the Drawings

[0014] Exemplary embodiments of the present invention are disclosed herein and illustrated by the drawings shown below. <00001​​​​​​​​​​​ [Figure 5] Figure 2 shows the working section of an endodontic instrument according to one embodiment. [Figure 6] Figure 5 shows a modified example of an endodontic instrument. [Figure 7] Another variation of an endodontic instrument is shown.

[0015] Examples Figure 1 shows an endodontic instrument 100 (or another type of tapered instrument) for cleaning a root canal. The endodontic instrument 100 comprises a working section 110 that extends substantially along the longitudinal axis 101 between the apical tip 103 of the endodontic instrument 100 and the shaft 104. The working section 110 is intended to engage with the root canal being treated. The endodontic instrument 100 may further comprise a shank (not shown) that is fixed to the shaft 104 and intended to be attached to a rotating support for rotating the endodontic instrument 100 around its longitudinal axis 101. Instead of a shank, the endodontic instrument 100 may comprise a handle for manually rotating the endodontic instrument 100. The working section 110 may comprise an apical segment 120 that is substantially linear with respect to the longitudinal axis 101 and an intermediate segment 130 that extends between the apical segment 120 and the shaft 104. The apical segment 120 and the intermediate segment 130 are arranged sequentially from the apical tip 103 toward the shaft 104.

[0016] The working section 110 is made of a nickel-titanium alloy, also known as nitinol, containing nickel and titanium in approximately equal atomic percentages. Nitinol is a shape-memory alloy that is deformable at low temperatures but returns to its previously deformed ("memorized") shape when heated. Nitinol can exhibit plasticity and superelasticity at different temperatures.

[0017] Nitinol alloys may include medical-grade nitinol containing 54.5% to 57% by weight of Ni, as defined, for example, in ASTM standard 2063:2018. Nitinol alloys may contain less than 0.1% by weight of other elements other than Ni and Ti.

[0018] Nitinol can be characterized by a crystallographic structure of interpenetrating simple cubic crystals called the austenite phase. Nitinol can also spontaneously transform into a more complex rhombohedral crystallographic structure known as the R phase. The transition between the R phase and the austenite phase occurs at a transition temperature (austenite completion temperature A). f It occurs in the following state. Below the transition temperature, nitinol is in the R phase and is plastic, and above the transition temperature, it is in the austenite phase and exhibits superelasticity. Superelastic alloys can be reversibly deformed under very high strains.

[0019] In one embodiment, the work section 110 is a first transition temperature T T1 At least a first portion 111 having a second transition temperature T T2 It comprises at least a second portion 112 having a first transition temperature T T1 The temperature is lower than the working temperature, and as a result, at the working temperature, the first part 111 is in the austenite phase. If the working part 110 is an endodontic instrument used in the root canal, the working temperature can correspond to body temperature. Here, body temperature means normal human body temperature, which is typically 36.5°C to 37.5°C. In fact, body temperature further corresponds to the operating temperature of the working part 110. Second transition temperature T T2 This is a temperature higher than body temperature, and as a result, at body temperature, the second portion 112 is in the R phase.

[0020] When using the endodontic instrument 100, the working part 110 is located inside the root canal and heated to body temperature. While inside the root canal, the first part 111 reaches a first transition temperature T T1 It exceeds the austenite phase. The first portion 111 is consequently hyperelastic. The second portion 112 is at the second transition temperature T T2 It is less than and in the R phase. The second part 112 is consequently plastic.

[0021] When the working section 110 enters the root canal, the austenite phase in the first section 111 can substantially rest the first section 111 relative to the second section 112, and may have improved cutting efficiency. The R phase allows the second section 112 to deform with low elastic feedback (plasticity) under radial constraint (no spring effect). The second section 112 has improved plasticity relative to the first section 111 and can act as a fulcrum for the first section 111.

[0022] When the working section 110 extends linearly (for example, as in the endodontic instrument 100 shown in Figure 1), the elastic first or second section 111, 112 minimizes angular deflection under torsional constraint. The other plastic second or first section 112, 111 provides a “pre-bending function” or guiding function only where required along the working section 110. This is particularly advantageous for instruments with small wire diameters.

[0023] In one possible configuration shown in Figure 1, the working section 110 comprises a second portion 112 extending along the apical segment 120 and a first portion 111 extending along the intermediate segment 130. When the working section 110 is in the root canal and heated to body temperature, the apical segment 120 is in the R phase and can be deformed in a low elastic feedback (plastic) state under radial constraint. The intermediate segment 130 is in the austenite phase and has improved elasticity relative to the apical segment 120.

[0024] In another possible configuration not shown, the working section 110 comprises a first portion 111 extending along the apical segment 120 and a second portion 112 extending along the intermediate segment 130.

[0025] In yet another possible configuration shown in FIG. 2, the working part 110 includes a plurality of first parts 111 and a plurality of second parts 112 arranged alternately. In the example of FIG. 1, the working part 110 includes two second parts 112 arranged between three first parts 111. The root tip segment 120 corresponds to the first part 111. The alternate arrangement of the first part 111 and the second part 112 can be reversed with respect to that shown in FIG. 2. In that case, the root tip segment 120 corresponds to the second part 112.

[0026] In one aspect, the first transition temperature T T1 can be less than 35° C., for example, a temperature below between 35° C. and 20° C.. The second transition temperature T T2 can be 39° C. or higher, for example, higher than a temperature between 39° C. and 45° C.. Alternatively, the first and / or second transition temperature T T1 , T T2 is near body temperature, for example, can be 32.5° C. to 35° C., and as a result, the first and / or second parts 111, 112 exhibit a shape memory effect, that is, the first and / or second parts 111, 112 are in the R phase at room temperature, are plastic, and are in the austenite phase at body temperature and exhibit superelasticity. Here, room temperature means a temperature of 20° C. to 25° C..

[0027] FIG. 3 shows an endodontic instrument 100 according to another embodiment, where the intermediate segment 130 includes a first curved portion 131 and a second curved portion 132. The endodontic instrument 100 is shown as including a shank 105 fixed to the shaft 104.

[0028] Figure 4 shows details of the working section 110 of the endodontic instrument 100 shown in Figure 3. The first curved section 131 has a first peak A1 with respect to the longitudinal axis 101, and the second curved section 132 has a second peak A2 with respect to the longitudinal axis 101. The first and second peaks A1 and A2 correspond to the maximum amplitudes of the first and second curved sections 131 and 132, respectively, i.e., the maximum distances of the first and second curved sections 131 and 132 with respect to the longitudinal axis 101. The first curved section 131 may curve along the same plane as the second curved section 132, but in opposite directions.

[0029] Furthermore, as shown in Figure 4, the apical segment 120 may have a tapered portion extending from the intermediate segment 130 to the apical tip 103. The apical envelope 125 of the apical segment 120 forms an apical taper angle α with respect to the longitudinal axis 101.

[0030] The first peak A1 and the second peak A2 are located at first and second distances D1 and D2, respectively, from the apical end 103 (towards the shaft 104). The first peak A1 may be smaller than the second peak A2, and as a result, the intermediate segment 130 may have a tapered shape from the shaft 104 toward the apical end 103. As shown in Figure 4, the intermediate envelope 135 of the intermediate segment 130 is tangent to the first and second peaks A1 and A2, forming an intermediate taper angle β with respect to the longitudinal axis 101.

[0031] In one embodiment, the apical taper angle α may be smaller than the intermediate taper angle β. A smaller apical taper angle α typically corresponds to the taper of thinner endodontic instruments used in the initial stages (when entering the root canal). A larger intermediate taper angle β of the intermediate envelope 135 corresponds to the taper of thicker endodontic instruments used in the final stages or multiple final stages of root canal treatment.

[0032] As described in the applicant's International Patent Publication No. 2022IB61697, the working section 110 having an intermediate envelope 135 can act as a whip to contact and brush the pipe wall, removing any soft material that may cover its surface. The function of the working section 110 is to clean the surface of the pipe wall, regardless of the shape of the pipe. The shape of the working section 110 allows for better removal of debris from inside the pipe.

[0033] In one embodiment shown in Figure 5, the working section 110 may comprise one second portion 112 positioned between the first peak A1 and the apical tip 103, one second portion 112 positioned between the first peak A1 and the second peak A2, and one second portion 112 positioned between the second peak A2 and the shaft 104. More generally, at least one second portion 112 may be positioned between the first peak A1 and the apical tip 103. At least one second portion 112 may be positioned between the first peak A1 and the second peak A2. At least one second portion 112 may be positioned between the second peak A2 and the apical tip 103. The apical segment 120 corresponds to the first portion 111.

[0034] In the configuration shown in Figure 5, the working section 110 has improved cleaning efficiency even in root canals having an elliptical or irregular cross-section. In fact, during the rotation of the endodontic instrument 100 (with continuous and / or reciprocating motion), inertial centrifugal force is generated in the eccentric portion of the working section 110 (e.g., the first and second curved portions 131, 132) that is not on the longitudinal axis 101 of the instrument. In this configuration, the eccentric portion can move freely in the radial direction due to the inelastic first portion 111 of the R phase.

[0035] The plastic first or second portion 111, 112 may act as a pre-bend to facilitate the entry of the working portion 110 into the root canal, and at the same time, strong cutting efficiency can be ensured in the first and second curved portions 131, 132 (due to the spring effect that presses the curved portions 131, 132 against the root canal wall).

[0036] Here again, the alternating arrangement of the first portion 111 and the second portion 112 can be reversed relative to that shown in Figure 5. In that case, the apical segment 120 corresponds to the second portion 112.

[0037] Figure 6 shows a modified example of the endodontic instrument 100 of Figure 5, in which the first inelastic R-phase portion 111 extends along the apical segment 120 and the second portion 112 extends along the intermediate segment 130. Alternatively, the second portion 112 may extend along the apical segment 120 and the first portion 111 may extend along the intermediate segment 130.

[0038] Figure 7 shows another modification of the endodontic instrument 100, where the working section 110 comprises four curved sections 131-134, each having peaks A1-A4. Peaks A1-A4 are defined with respect to the longitudinal axis 101 and correspond to the maximum amplitude of the curved sections 131-134 with respect to the longitudinal axis 101. Other geometries are also possible. For example, the working section 110 may have three curved sections or more than four curved sections.

[0039] Similar to the configuration in Figure 5, the first portion 111 and the second portion 112 may be positioned between peaks A1-A4, resulting in the presence of an inelastic portion of the R phase or a hyperelastic portion of the austenite phase between peaks A1-A4. Alternatively, the inelastic first portion 111 of the R phase may extend along the apical segment 120, and the second portion 112 may extend along the intermediate segment 130. Furthermore, the second portion 112 may extend along the apical segment 120, and the first portion 111 may extend along the intermediate segment 130.

[0040] It is understood that the present invention is not limited to the exemplary embodiments described above, and other embodiments are possible within the scope of the claims.

[0041] For example, endodontic instruments may include expanders, compactors, auxiliary instruments, shaping and cleaning devices. The present invention may further relate to dental tools or instruments made of a nitinol alloy, wherein the nitinol alloy of the working portion 110 is capable of transitioning from the R phase to an austenite phase alloy state when heated above its transition temperature. The dental tools or instruments may include orthodontic tools or instruments, orthodontic wires, matrix bands, or retainers. The working portion 110 may constitute all or part of an endodontic instrument or dental tool or instrument.

[0042] In one embodiment, a method for forming an endodontic instrument 100 is: First or second transition temperature T T1 , T T2 To provide a nitinol alloy having; Local heat treatment is performed on at least a portion of the work area 110, thereby bringing the work area 110 to a first transition temperature T T1 A first portion 111 having at least one first part 111 and a second transition temperature T T2 This includes including at least one second part 112 having

[0043] In one embodiment, the local heat treatment includes locally heating the workpiece 110 to produce a first portion 111 or a second portion 112.

[0044] Localized heat treatment may include scanning a laser beam along a surface region corresponding to a first portion 111 or a second portion 112. The laser beam scanning may be performed using a two-dimensional laser scanning unit. The laser beam scanning may be performed in an air atmosphere or other gas composition. The laser beam may be scanned along a longitudinal axis between 0.5 mm and 5 mm.

[0045] In one embodiment, the local heat treatment involves a laser pulse time of 1 ms to 20 s and a local heating temperature T of 300°C to 600°C when generating the first portion 111. HLThis can be performed at a temperature of 350°C to 800°C if it generates the second part 112.

[0046] In one specific example, the laser pulse may be emitted at an output of approximately 120 W. The laser beam is approximately 10 3 A region of mm is scanned. The laser irradiation time is 0.5 s to 1 s. The laser-irradiated region reaches a temperature of 500°C to 700°C. Local heat treatment is performed to an austenite completion temperature A of less than 20°C. f It can be executed to obtain.

[0047] Alternatively, localized heat treatment can be performed using localized induction heating or other rapid localized heat treatment processes.

[0048] The localized heat treatment can locally heat the first portion 111 or the second portion 112 without affecting the rest of the work area 110. In practice, since nitinol alloys readily propagate heat, the localized heat treatment should be performed in a very short time.

[0049] The method may further include performing an initial heat treatment on the entire workpiece 110 to generate a first portion 111 on the entire workpiece 110, or to generate a second portion 112 on the entire workpiece 110.

[0050] The initial heat treatment involves placing at least the working section 110 in the oven and heating it to an initial temperature of 300°C to 600°C to produce the first part 111. HI The process includes heating the working section 110 to 350°C to 800°C to produce the second section 112. The entire dental tool or instrument may be placed inside the oven. The initial heat treatment may be performed in an air atmosphere, or in an inert gas such as nitrogen (N), or in another gas composition, and is selected according to the desired surface treatment (e.g., formation of titanium oxide).

[0051] The initial heat treatment is performed during an initial time period P of 20 to 120 minutes. HIThis can be performed during the following period. In one particular example, the initial heat treatment is performed at 400°C for 1 hour. This initial heat treatment is performed at an austenite completion temperature of approximately 40°C A f It brings about.

[0052] The initial heat treatment is performed so that the entire working section 110 reaches a first transition temperature T T1 It may be configured to be characterized by (the entire working area 110 corresponds to the first part 111). Then the second transition temperature T T2 One or more second portions having the same properties may be added locally along the work area 110. Alternatively, the first heat treatment may bring the entire work area 110 to a second transition temperature T T2 It may be configured to be characterized by (the entire working area 110 corresponds to the second part 112). Then the first transition temperature T T1 One or more first portions having the same feature can be added locally along the workpiece 110 using localized heat treatment.

[0053] Alternatively, the first heat treatment is performed at a first heating temperature T H1 This can be carried out in a heated mold 30 (see Figure 6). Here, only the workpiece 100 can be inserted into the mold 30. If the workpiece 110 has the profile shown in Figures 3-5, the first heat treatment can be carried out in a mold 30 having a shape corresponding to that profile. Molding the workpiece 110 into a molded shape having at least one curved portion 131, 132 can be achieved by applying a small amount of pressure to the workpiece 110 that is sufficient to guide the workpiece 110 to follow the contour of the mold 30.

[0054] Initial heating temperature T HI and local heating temperature T HL This is the desired first transition temperature T T1 and the second transition temperature T T2It depends on the transition temperature T. For example, initial heat treatment or local heat treatment may be configured to alter the microstructure of nitinol by the appearance of a Ni-rich phase Ni4Ti3 when nitinol is at working temperature (such as body temperature). The Ni-rich phase Ni4Ti3 reduces the amount of Ni in the nitinol matrix, promotes the appearance of the R phase, and also affects the transition temperature T. T1 , T T2 This has the effect of increasing the transition temperature T. Subsequently, a second or first heat treatment may be configured to dissolve the Ni4Ti3 phase and allow Ni to return to the nitinol matrix. The increase in the Ni content in the nitinol matrix has the effect of increasing the transition temperature T. T2 , T T1 This reduces the R phase, and the R phase is replaced by the austenite phase.

[0055] In configurations not shown, the initial heat treatment is performed at an initial heating temperature T HI The process may be carried out over the entire workpiece 100 using a mold heated to a local heating temperature T. Here, only the workpiece 100 is inserted into the mold. Furthermore, the mold may include at least one mold section configured to perform local heat treatment on the workpiece 110. This mold section applies local heating temperature T to the workpiece 110. HL The work unit 100 may be placed inside a mold, after which initial heat treatment and localized heat treatment may be performed sequentially. [Explanation of symbols]

[0056] 11 Shank 12 Proximal end 13. Distal end 100 Endodontic Instruments 101 Instrument longitudinal axis 103 Apical tip 104 Shaft 105 Shank, Handle 110 Work Unit 111 Part 1 112 Part 2 120 Apical segment 130 Middle section 131 First curved section 132 Second curved section 135 Intermediate Envelope 20 Cutting surface α Apical taper angle β Intermediate taper angle A1 First peak A2 Second peak D1 First distance D2 Second distance T H1 First transition temperature T H2 Second transition temperature T HI Initial heating temperature T HL Local heating temperature

Claims

1. A dental tool or instrument (100) comprising a working part (110) made of a nitinol alloy, Here, the nitinol alloy of the work section (110) is capable of transitioning from the R phase to the austenite phase alloy state when heated above the transition temperature. Here, the work unit (110) controls the first transition temperature (T Ｔ１ At least a first portion (111) having ) and a second transition temperature (T Ｔ２ It includes at least a second portion (112) having ) The first transition temperature (T Ｔ１ ) is at a lower temperature than the working temperature of the working section (110), and as a result, at the working temperature, the first part (111) is in the austenite phase. Said second transition temperature (T Ｔ２ A dental tool or instrument wherein the temperature is higher than the working temperature, so that the second portion (112) is in the R phase at the working temperature.

2. The instrument includes an endodontic instrument (100), wherein the working part (110) is intended to engage with the root canal, and the working part (110) extends generally along the longitudinal axis (101) between the root apex (103) and the shaft (104). Here, the aforementioned working temperature is a dental tool or instrument between 36.5°C and 37.5°C (body temperature).

3. The aforementioned work unit (110) The root apical portion (120) is substantially linear with respect to the longitudinal axis (101), It includes the apical segment (120) and the intermediate segment (130) extending between the shaft (104), Here, the work unit (110) One of the first portion or the second portion (111, 112) extending along the apical segment (120), The dental tool or instrument according to claim 2, comprising a second portion or the other of the first portions (112, 111) each extending along the intermediate segment (130).

4. The working section (110) has a root apical portion (120) that is substantially linear with respect to the longitudinal axis (101), It includes the apical segment (120) and the intermediate segment (130) extending between the shaft (104), The work section (110) includes a plurality of first parts (111) and a plurality of second parts (112) arranged alternately. The dental tool or instrument according to claim 2 or 3.

5. The aforementioned intermediate segment (130) A first curved portion (131) having a first peak (A1) with respect to the longitudinal axis (101), It includes a second curved portion (132) having a second peak (A2) with respect to the longitudinal axis (101) and being larger than the first peak (A1), The working section (110) has either a first portion or a second portion (111, 112) that extends along the apical segment (120), Including a second portion or one of the first portions (112, 111) that extends along the intermediate segment (130), The dental tool or instrument according to claim 4.

6. The aforementioned intermediate segment (130) A first curved portion (131) having a first peak (A1) with respect to the longitudinal axis (101), It includes a second curved portion (132) having a second peak (A2) with respect to the longitudinal axis (101) and being larger than the first peak (A1), The dental tool or instrument according to claim 4, wherein at least one of the first portion or the second portion (111, 112) is positioned between the first peak (A1) and the root apex (103), between the first portion and the second peak (A1, A2), and between the second peak (A2) and the shaft (104).

7. The apical envelope (125) of the apical segment (120) forms an apical taper angle (α) with respect to the longitudinal axis (101). The intermediate envelope (135) of the intermediate segment (130) is tangent to the first and second peaks (A1, A2) and forms an intermediate taper angle (β) with respect to the longitudinal axis (101). The dental tool or instrument according to claim 5 or 6, wherein the apical taper angle (α) is smaller than the intermediate taper angle (β).

8. The first transition temperature (T Ｔ１ ) is 35°C or lower, for example, 32.5°C to 35°C, Said second transition temperature (T Ｔ２ ) is higher than 39℃ A dental tool or instrument according to any one of claims 1 to 7.

9. The first and / or second transition temperature (T Ｔ１ , T Ｔ２ ) is above 32.5°C to 35°C. A dental tool or instrument according to any one of claims 1 to 7.

10. A dental tool or instrument according to any one of claims 1 to 9, comprising an orthodontic tool or instrument, an orthodontic wire, a matrix band, or a retainer.

11. To provide a nitinol alloy having a first or second transition temperature (T Ｔ１ , T Ｔ２ ), and Local heat treatment is performed on at least a portion of the work section (110), thereby bringing the work section (110) to a first transition temperature (T Ｔ１ A first portion (111) having ) and a second transition temperature (T Ｔ２ A method for manufacturing a dental tool or instrument according to any one of claims 1 to 10, comprising including at least one second portion (112) having )

12. The method according to claim 11, wherein the local heat treatment includes locally heating the work area (110) to produce a first portion or a second portion (111, 112).

13. The method according to claim 12, wherein the localized heat treatment includes scanning a laser beam along a surface region corresponding to the first or second portion (111, 112).

14. The local heat treatment involves a laser pulse time of 1 ms to 20 s, and a local heating temperature of 300°C to 600°C (T) when generating the first portion (111). ＨＬ The method according to claim 13, wherein the process is carried out at 350°C to 800°C when generating the second portion (112).

15. The method according to claim 11 or 12, comprising performing an initial heat treatment on the entire work section (110) to generate the first portion (111) on the entire work section (110), or generating the second portion (112) on the entire work section (110).

16. If the initial heat treatment involves placing at least the work section (110) inside the oven and generating the first portion (111), the initial heating temperature is 300°C to 600°C (T ＨＩ The method according to claim 13, further comprising heating the work section (110) with a 350°C to 800°C when generating the second portion (112).

17. The initial heat treatment is performed for an initial time period of 20 to 120 minutes (P ＨＩ The method according to claim 16, which is performed during )

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