Endodontic treatment device with improved suitability of tooth tube geometry

Abstract

The present disclosure relates to an endodontic treatment device (100) made of a shape memory alloy and having a working part (110). The working member (110) has a working profile comprising a substantially straight root tip segment (120) and an intermediate segment (130). The intermediate segment (130) is composed of a first curved portion (131) having a first peak (A1) and a second curved portion (132) having a second peak (A2) larger than the first peak (A1). The apical envelope (125) of the apical segment (120) forms an apical cone angle (alpha) with respect to the longitudinal axis (101). The intermediate envelope (135) of the intermediate segment (130) tangent to the first peak (A1) and the second peak (A2) forms an intermediate angle (alpha) with respect to the longitudinal axis (101), the root angle (beta) being smaller than the intermediate angle (beta).

Description

Technical Field

[0001] The present invention relates to the field of endodontic treatment, and more particularly, to an improved endodontic treatment instrument for operating within tooth canals, dental pulp, and surrounding areas, and even more particularly, to an endodontic treatment instrument that better adapts to the geometry of tooth canals and allows for better removal of debris from the canals. Background Art

[0002] For the purpose of receiving filling material, the root canals of teeth are typically cleaned and shaped with the aid of endodontic treatment instruments having a cutting section or so-called working part. The purpose of the working part is to form, trim, and clean the inner wall of the root canal in order to prepare it for receiving a treatment material and then a filling material, so as to exclude any oxygen that might allow bacteria to grow in the tooth, especially near the root.

[0003] The working part of an endodontic treatment instrument typically has an approximately cylindrical or conical envelope, which has an axially symmetric geometry of a file. And one or more cutting edges are helically wound around the working part. The endodontic treatment instrument can be configured to "scrape" the wall of the root canal, in other words, cut into the dentin without modifying the natural shape of the canal by following its path. However, recent studies have shown that excessive removal of dentin is not recommended, as the result of this procedure is that the tooth is weakened.

[0004] Root canal morphology varies greatly among patients. The longitudinal canal profile typically has an irregular elliptical cross-section along its length and can include one or more narrow and curved sections.

[0005] Most current endodontic treatment instruments have a straight geometry and can have a certain flexibility, enabling them to adapt to the longitudinal profile of the root canal to some extent. However, when the latter varies in curvature and cross-section, this flexibility does not guarantee effective cleaning of the entire wall.

[0006] Furthermore, due to the axially symmetric geometry of the instrument, the envelope of the space swept by a standard endodontic treatment instrument driven by rotation about its longitudinal axis is approximately cylindrical or conical, such that the walls of a root canal having an elliptical cross-section cannot be swept by a single endodontic treatment instrument, but rather a series of endodontic treatment instruments with different diameters is required. Thus, the practitioner is forced to change endodontic treatment instruments during the procedure, starting with a small diameter and then gradually moving to a larger diameter, which is not only cumbersome but also does not guarantee effective cleaning of the wall without damaging the dentin.

[0007] Accordingly, there is a need for an endodontic instrument to meet the needs of practitioners, namely, an endodontic instrument that is flexible enough to follow the contour of the canal, has a geometry that allows it to contact rough and uneven areas of the canal wall, and brushes against the canal wall to remove internal biofilm without cutting into the dentin.

[0008] From a material perspective, endodontic instruments have typically been made from medical-grade metals, including stainless steel and various wrought alloys. Modern endodontic instruments are made from shape memory alloys, such as nickel-titanium alloys, including "Nitinol" TM " or "NiTi". Compared to stainless steel instruments, endodontic instruments made from nickel and titanium exhibit excellent flexibility and torsional properties.

[0009] Document WO2016004541A1 discloses an endodontic instrument for cleaning root canals that follows the natural geometry of the canal. The endodontic instrument includes a working section made from a shape memory alloy having a transformation temperature. The shape memory alloy can be deformed below the transformation temperature but returns to its pre-deformed ("memory") shape when heated to be at or above the transformation temperature. The working section includes a free end section that will engage within the root canal and a second active segment. When below the transformation temperature, the second active segment is substantially straight, and when at or above the transformation temperature, the second active segment has a curved shape configured to contact and brush against the surface of the canal wall. Summary of the Invention

[0010] The present disclosure relates to an endodontic instrument for cleaning root canals. The endodontic instrument is made from a shape memory alloy and has a working part that will engage within the root canal and generally extends between the root tip and the shank along a longitudinal axis. The working part has a working profile that includes an apical segment that is substantially straight relative to the longitudinal axis and an intermediate segment that extends between the apical segment and the shank. The intermediate segment is composed of a first curved part and a second curved part. The first curved part has a first peak relative to the longitudinal axis, and the second curved part has a second peak relative to the longitudinal axis and greater than the first peak. The apical envelope of the apical segment forms an apical cone angle relative to the longitudinal axis, and the intermediate envelope of the intermediate segment that is tangent to the first peak and the second peak forms an intermediate angle relative to the longitudinal axis, and the apical angle is less than the intermediate angle.

[0011] The working part of the endodontic instrument allows the endodontic instrument to better adapt to the tooth canal geometry and increases the removal of debris from the canal. The working part of the endodontic instrument can be easily introduced into the root canal. Brief Description of the Drawings

[0012] Exemplary embodiments of the present invention are disclosed in the description and illustrated by the drawings, wherein: Figure 1Illustrates an endodontic treatment instrument including a working part according to one embodiment; Figure 2 Illustrates a working part having a working profile according to one embodiment; and Figure 3 Displays a graph reporting the transition temperature of a nitinol alloy containing 56% nickel and approximately 44% titanium by weight. DETAILED DESCRIPTION

[0013] Figure 1 Illustrates an endodontic treatment instrument 100 for cleaning a root canal according to one embodiment. The endodontic treatment instrument 100 includes a working part 110 that extends generally along a longitudinal axis 101 between a root tip 103 and a shank 104 of the endodontic treatment instrument 100. The working part 110 will engage in the root canal to be treated. The endodontic treatment instrument 100 further includes a handle 105 that is fixed to the shank 104 and will be mounted on a rotary bracket to rotate the endodontic treatment instrument 100 about its longitudinal axis 101. Instead of a handle, the endodontic treatment instrument 100 may include a handgrip 105 for manually rotating the endodontic treatment instrument 100.

[0014] Figure 2 Illustrates a working profile according to one embodiment. The working profile of the working part 110 includes a root tip segment 120 that is substantially straight relative to the longitudinal axis 101, and an intermediate segment 130 that extends between the root tip segment 120 and the shank 104. The root tip segment 120 and the intermediate segment 130 are arranged in sequence from the root tip 103 to the shank 104.

[0015] The root tip segment 120 may have a tapered section that extends from the intermediate segment 130 towards the root tip 103. As Figure 2 shown, the root tip envelope 125 of the root tip segment 120 forms a root tip cone angle α relative to the longitudinal axis 101.

[0016] The intermediate segment 130 is composed of a first curved portion 131 and a second curved portion 132. The first curved portion 131 has a first peak A1 relative to the longitudinal axis 101, and the second curved portion 132 has a second peak A2 relative to the longitudinal axis 101. The first peak A1 and the second peak A2 correspond to the maximum amplitudes of the first curved portion 131 and the second curved portion 132, respectively, i.e., the maximum distances of the first curved portion 131 and the second curved portion 132 relative to the longitudinal axis 101.

[0017] In one possible configuration, the first curved portion 131 may bend in the same plane as the second curved portion 132 but in opposite directions.

[0018] The first peak A1 and the second peak A2 are located at a first distance D1 and a second distance D2, respectively, from the root tip 103 (towards the rod 104). The first peak A1 is smaller than the second peak A2, such that the intermediate segment 130 has a tapered shape from the rod 104 towards the root tip 103. As Figure 2 shown, an intermediate envelope 135 of the intermediate segment 130 that is tangent to the first peak A1 and the second peak A2 forms an intermediate cone angle β with respect to the longitudinal axis 101.

[0019] In one aspect, the root tip cone angle α is smaller than the intermediate cone angle β. The small root tip cone angle α corresponds to the taper of a relatively narrow endodontic instrument typically used in an earlier stage (when entering the canal). The larger intermediate cone angle β of the intermediate envelope 135 corresponds to the taper of a relatively wide endodontic instrument used in one or more final stages of root canal surgery.

[0020] The endodontic instrument 100 can be considered a non-uniformly tapered instrument (or a type 4 non-standard instrument according to International Standard ISO 3630-1, Third Edition, August 2019 (Section 4)). The endodontic instrument 100 can further be considered a K-type reamer according to the same international standard (Section 8).

[0021] The working part 110 with the intermediate envelope 135 can act as a whip that brushes against the wall of the canal and removes soft parts that may be arranged on its surface. The function of the working part 110 is to clean the surface of the canal wall, regardless of the geometry of the canal. The shape of the working part 110 allows for better removal of debris in the canal.

[0022] The effective taper, i.e., the root tip cone angle α and the intermediate cone angle β, can be constant or variable along the length of the working part 110.

[0023] In one aspect, the root tip cone angle α can be between 0° and 7°. The intermediate cone angle β can be between 4° and 30°.

[0024] In one aspect, the length of the root tip segment 120 is between approximately 2 mm and 5 mm.

[0025] The ratio of the first distance D1 to the length of the working part 110 is between 0.45 and 0.18.

[0026] The ratio of the second distance D2 to the length of the working part 110 is between 0.65 and 0.3.

[0027] For example, in the case of a K-type endodontic instrument with a 16-mm long working part 110, the root tip segment 120 can have a length between 3 mm and 5 mm. The first distance D1 can be between 3 mm and 7 mm. The second distance D2 can be between 5 mm and 10 mm.

[0028] In a preferred configuration, the apical segment 120 of the endodontic instrument 100 is coaxial with the longitudinal axis 101. The working part 110 is also preferably coaxial with the longitudinal axis 101.

[0029] The endodontic instrument 100 preferably includes cutting edges 20 along the working part 110. The cutting edges 20 are intended to cut the material along the walls of the root canal. The cutting edges 20 can be helical cutting edges, such as those in conventional helical endodontic instruments, or other cutting edges known in the art. Alternatively, the cutting edges 20 can be angled corners extending along a part of the length of a polygonal fluteless bar. In some embodiments, the cutting edges 20 are alternately or selectively patterned based on the profile of the specific working part 110 of the endodontic instrument 100.

[0030] In some embodiments, the apical segment 120 can be terminated at the root tip 103 by a tip 121 that does not include a cutting edge. The tip 121 can be rounded. The tip can include an angled cutting area such that the tip is configured to perform the function of guiding and cutting the endodontic instrument in the canal, as described by the present applicant in International Patent Application WO2021240387A1.

[0031] The endodontic instrument 100 can be made of a shape memory alloy having a transformation temperature. Below the transformation temperature, the working part 110 of the endodontic instrument 100 is ductile and can be plastically deformed. Above the transformation temperature, the working part 110 reverts to the memory shape and exhibits elasticity.

[0032] The working profile of the working part 110 can be obtained during the manufacture of the endodontic instrument 100. More specifically, a molding or shaping operation can be performed on the working part 110 of the endodontic instrument 100 to make it into a molded shape corresponding to the working profile. During molding, the working part 110 is heated to a heating temperature, for example, between 400 °C and 600 °C, to memorize the molded shape.

[0033] In a preferred embodiment, the shape memory alloy of the endodontic instrument 100 can have a transformation temperature close to body temperature. For example, the transformation temperature can be around 30 °C to 36 °C. When the endodontic instrument 100 is introduced into the root canal, the endodontic instrument 100 is at a temperature close to room temperature and below the transformation temperature. Once inside the canal, the working part 110 is heated by the body temperature, which is at or above the transformation temperature of the shape memory alloy. The working part 110 obtains the working profile. The latter is adapted for canal treatment operations. Depending on the shape memory alloy, the working part 110 may become elastic when at or above the transformation temperature and plastically deformable when below the transformation temperature.

[0034] In one embodiment, the endodontic instrument 100 is made of nitinol alloy (e.g., typically about 56% nickel and about 44% titanium by weight). The nitinol alloy is in the R-phase below the transformation temperature and in the austenite phase above the transformation temperature. In the R-phase, the nitinol alloy is malleable and can be temporarily plastically deformed into a desired shape. The endodontic instrument 100 may also have superelastic properties, which are obtained by selecting the alloy and through specific processing, particularly heat treatment. Figure 3 A graph showing the transformation temperatures of a nitinol alloy reported to contain 56% nickel and about 44% titanium by weight. The nitinol alloy has a first transformation temperature for the martensite phase to the R-phase and a second transformation temperature for the R-phase to the austenite phase. The first transformation temperature is about -60°C.

[0035] In one embodiment, the endodontic instrument 100 may be formed by heat-treating the nitinol alloy such that its transformation temperature is between 15°C and 45°C. The endodontic instrument 100 may be further formed by memorizing the working profile of the working part 110, i.e., a profile including: a straight apical segment 120, and an apical segment 120 and an intermediate segment 130, which are composed of a first bending portion 131 and a second bending portion 132. This method of forming the endodontic instrument 100 is described in the applicant's U.S. Patent US9931179B2. Following this forming method, when the endodontic instrument 100 transforms from the martensite phase to the austenite phase, i.e., when the temperature is at or above the transformation temperature of the nitinol alloy, the working part 110 adopts the working profile. Reference numbers used in the drawings 100 Endodontic instrument 101 Instrument longitudinal axis 103 Root tip 104 Rod 105 Handle 110 Working part 110 Working section 120 Apical segment 121 Tip 125 Apical envelope 130 Intermediate segment 131 First bending portion 132 Second bending portion 135 Intermediate envelope 20 Cutting surface α Apical cone angle β Intermediate cone angle A1 First peak A2 Second peak D1 First distance D2 Second distance.

Claims

1. An endodontic treatment instrument (100) for cleaning the root canal; The endodontic treatment instrument (100) is made of shape memory alloy and has a working part (110) that will engage in the root canal and generally extends between the root tip (103) and the shank (104) along the longitudinal axis (101); The working part (110) has a working profile that includes an apical segment (120) that is substantially straight relative to the longitudinal axis (101), and an intermediate segment (130) that extends between the apical segment (120) and the shank (104); Wherein the intermediate segment (130) is composed of a first bending portion (131) and a second bending portion (132), the first bending portion has a first peak (A1) relative to the longitudinal axis (101), and the second bending portion has a second peak (A2) relative to the longitudinal axis (101) and greater than the first peak (A1); Wherein the apical envelope (125) of the apical segment (120) forms an apical cone angle (α) relative to the longitudinal axis (101), and the intermediate envelope (135) of the intermediate segment (130) that is tangent to the first peak (A1) and the second peak (A2) forms an intermediate angle (β) relative to the longitudinal axis (101), and the apical angle (α) is less than the intermediate angle (β).

2. The endodontic treatment instrument according to claim 1, Wherein the apical segment (120) has a length between 2 mm and 5 mm.

3. The endodontic treatment instrument according to claim 1 or 2, Wherein the first distance (D1) from the first peak (A1) to the root tip (103) is between 5 mm and 8 mm.

4. The endodontic treatment instrument according to any one of claims 1 to 3, Wherein the second distance (D2) from the second peak (A2) to the root tip (103) is between 5 mm and 12 mm.

5. The endodontic treatment instrument according to any one of claims 1 to 4, Wherein the apical cone angle (α) is between 0% and 7%.

6. The endodontic treatment instrument according to any one of claims 1 to 5, Wherein the intermediate cone angle (β) is between 4% and 30%.

7. The endodontic treatment instrument according to any one of claims 1 to 6, Wherein the apical segment (120) is coaxial with the longitudinal axis (101).

8. The endodontic treatment instrument according to any one of claims 1 to 7, Wherein the working part (110) is coaxial with the longitudinal axis (101).

9. The endodontic treatment instrument according to any one of claims 1 to 8, Wherein the first bending portion (131) and the second bending portion (132) are bent along the same plane but in opposite directions.

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