A three-dimensional self-adjusting root canal file and its processing technology

Abstract

This invention discloses a three-dimensional self-adjusting root canal file and its processing technology. First, two or more identical materials are drawn together to form a composite blank, which serves as the raw material for the root canal file. Then, a handle, connecting rod, and file body are machined from different parts of the composite blank. The advantage of this process lies in its ingenious use of a composite blank to combine two different or identical metal materials with high strength and complete seamlessness, achieving a bonding strength far superior to adhesive or mechanical assembly methods. Because the entire blank is directly processed by subtraction, the processing precision is much higher than when processing two components and assembling them. This invention uses methods such as drilling and inserting wire, sleeve cutting, or sleeve inserting to create metal brush filaments with outwardly flared free ends on the mandrel of a metal rod. Combined with the drawing and composite manufacturing process of the metal rod and metal tube, the metal brush filaments are simultaneously drawn and annealed with the mandrel and metal tube, ensuring a firm connection between the metal brush filaments and the mandrel.

Description

Technical Field

[0001] This invention relates to the field of medical devices, specifically to a root canal file and its processing technology that can adapt to the internal morphology of a tooth root canal and perform three-dimensional self-adjustment in the shape of the file body. Background Technology

[0002] Machine-operated titanium-nickel alloy root canal files emerged in the 1990s and began to be widely used in my country around 2010, greatly improving the level and efficiency of root canal treatment in endodontics. They offer significant advantages over traditional stainless steel root canal files, especially in the preparation of complex and small root canals. Because nickel-titanium alloy files have better elasticity, lower hardness, and greater flexibility than stainless steel files, they can complete root canal preparation in a shorter time while avoiding excessive cutting of the dentin within the root canal, making them highly favored by dental clinicians.

[0003] Currently available nickel-titanium alloy root canal files are mostly manufactured through methods such as twisting, grinding, and chemical treatment. The file body is a single-stranded, threaded cone shape, with a triangular or rectangular cross-section featuring protrusions. During root canal treatment, the file body, driven by a root canal motor, rotates at high speed within the patient's root canal. The protrusions of the file body cut against the root canal wall during rotation, achieving efficient cleaning and preparation of the root canal, laying a foundation for subsequent root canal treatment steps. However, because the rotation trajectory of the root canal file is circular, while the cross-sectional shape of most root canals is elliptical or eye-shaped, conventional nickel-titanium root canal files are insufficient for adequately cleaning and preparing the edges and corners of the root canal.

[0004] To achieve more thorough cleaning and preparation of the root canal during root canal treatment, a US patent (publication number: US20030099916A1) discloses a flocked root canal file. A flocked root canal file involves flocking the outer surface of the flocked section of the file body to thoroughly clean the root canal area, capture loose debris, and remove it from the root canal, thus achieving the purpose of cleaning the root canal. Typically, the flocking material is flexible fiber adhered to the file body or metal wire welded to it. However, because the fibers and wires are only attached to the outer surface of the file body, the connection points are small, resulting in insufficient connection strength. During the high-speed rotation of the file body during the procedure, they are prone to detaching and falling into the root canal, not only failing to achieve the desired cleaning effect but also allowing foreign objects to enter the root canal.

[0005] Flexible fibers are also prone to wear and tear. Under high-speed rotation, they are difficult to cut the inner wall of the root canal and cannot completely remove plaque, debris, calculus, etc. attached to the inner wall of the root canal. Therefore, it is difficult to meet the requirement of thorough cleaning of the root canal for root canal preparation. Summary of the Invention

[0006] This invention addresses the shortcomings of existing technologies by proposing a three-dimensional self-adjusting root canal file with metal bristles. This involves first fabricating a preform by bonding multiple layers of material to a metal rod with embedded metal bristles, and then machining the handle and file body separately from different parts of the same preform. The invention also describes the manufacturing process of this root canal file. Compared to existing technologies that attach fibers or metal bristles to the file body through bonding or welding, the metal bristles of this invention are less prone to detachment when elastically bending and deforming according to the shape of the root canal. This significantly improves the structural strength of the metal bristles, surgical precision and effectiveness, and reduces the probability of failure during clinical use.

[0007] The technical solution of the present invention is as follows:

[0008] A manufacturing process for a three-dimensional self-adjusting root canal file includes the following steps:

[0009] S1 manufactures a metal rod, and then creates metal filaments on the surface of the core rod;

[0010] S2 fabricates a composite preform, which includes a metal tube and a metal rod. The metal rod is placed in the metal tube and drawn and annealed in one piece, so that the metal tube forms a dense wrap around the metal rod.

[0011] S3 cold-draws the composite embryo until its diameter is slightly larger than or equal to the maximum diameter of the root canal file.

[0012] S4 divides the composite blank into two parts: a handle and a file; remove the outer metal tube of the file to expose the inner metal rod;

[0013] S5 shapes the metal brush filaments on the metal rod.

[0014] In step S1, the mandrel is a hollow tube, and holes are drilled in the mandrel to insert metal brush filaments into the holes; part of the metal brush filaments are inside the holes, and part of them are attached to the outer surface of the mandrel.

[0015] In step S1, the metal rod is formed by nesting multiple layers of tubing outside the core rod.

[0016] In step S4, in addition to the mandrel, the tube is cut into multiple rings along the circumferential direction, and a portion of the rings away from the handle is cut into thin strips along the axial direction.

[0017] In step S1, multiple rings are spaced apart on the outer surface of the mandrel, and metal brush filaments are inserted between the rings and the mandrel; the free ends of the metal brush filaments extend beyond the rings.

[0018] The metal bristles on each of the rings may extend in the same or different directions.

[0019] A three-dimensional self-adjusting root canal file manufactured using the aforementioned process is characterized in that: it comprises a metal tube and a metal rod, the inner surface shape of the metal tube matching the outer surface shape of the metal rod; the metal rod is placed inside the metal tube, and the metal tube forms a dense enclosure around the metal rod; the metal tube portion of the file body is removed, exposing the inner metal rod; and the surface of the metal rod is provided with metal bristles with free ends extending outwards.

[0020] A three-dimensional self-adjusting root canal file manufactured using the aforementioned process is characterized in that: it comprises a metal tube and a metal rod, the inner surface shape of the metal tube matching the outer surface shape of the metal rod; the metal rod is placed inside the metal tube, and the metal tube forms a dense enclosure around the metal rod; the metal tube of the file body portion of the root canal file is removed, exposing the inner metal rod; the metal rod is a hollow mandrel with a hole, one end of which is inserted into the hole, and the other end of which is spread outward to form metal bristles.

[0021] A three-dimensional self-adjusting root canal file manufactured using the aforementioned process is characterized in that: it comprises a metal tube and a metal rod, the inner surface shape of the metal tube matching the outer surface shape of the metal rod; the metal rod is placed inside the metal tube, and the metal tube forms a dense enclosure around the metal rod; the metal tube of the file body portion of the root canal file is removed, exposing the inner metal rod; multiple layers of tubing are nested around the core of the metal rod, the tubing being cut into multiple circular rings, and the portion of the circular rings away from the handle being cut into thin strips; the free ends of the thin strips open outwards to form metal bristles.

[0022] A three-dimensional self-adjusting root canal file manufactured using the aforementioned process is characterized in that: it comprises a metal tube and a metal rod, the inner surface shape of the metal tube matching the outer surface shape of the metal rod; the metal rod is placed inside the metal tube, and the metal tube forms a dense enclosure around the metal rod; the metal tube of the file body portion of the root canal file is removed, exposing the inner metal rod; multiple rings are spaced apart on the outer surface of the mandrel of the metal rod, and metal bristles are inserted between the rings and the mandrel; the free ends of the metal bristles extend beyond the rings.

[0023] The technical effects of this invention are as follows:

[0024] This invention relates to a three-dimensional self-adjusting root canal file manufacturing process. Addressing the drawbacks of root canal files with circular rotation trajectories, high rotation speeds, and the tendency for attached fibers or metal bristles to detach, this invention proposes a composite preform process for root canal files with metal bristles. The file blank is a composite preform formed by drawing and bonding two or more identical materials. The handle, connecting rod, and file body are then machined separately from different parts of the composite preform. The advantage of this process lies in its ingenious use of a composite preform method to combine two different or identical metal materials in a high-strength and completely seamless manner, achieving a bond strength far superior to adhesive bonding and mechanical assembly methods. When manufacturing the file body and handle, because the entire blank is directly subtracted, the manufacturing process is continuous and without cumulative errors. Therefore, the manufacturing precision is much higher than when the handle and file body are machined separately and then assembled.

[0025] The composite preform of the three-dimensional self-adjusting root canal file of the present invention is formed by repeatedly and synchronously drawing and annealing a metal rod into a metal tube, so that the metal rod and the metal tube are moderately deformed, and the metal tube tightly wraps the metal rod or metal rod bundle inside it, thereby forming a stable connection structure between the metal tube and the metal rod.

[0026] Furthermore, because the shape of the inner surface of the metal tube matches the shape of the outer surface of the metal rod, the cross-sectional shape of the metal rod is circular, elliptical, or polygonal with protrusions. During root canal surgery, when using a root canal file for drilling, the metal tube tightly wraps around the metal rod, preventing relative displacement between the file body and the handle. Even without welding or bonding between the metal tube and the metal rod, the root canal file maintains extremely high maneuverability during surgery.

[0027] This invention utilizes methods such as perforation and wire insertion, cannulation cutting, or cannulation wire insertion to fabricate metal brush filaments with their free ends flaring outwards on a metal rod mandrel. By combining a metal rod and metal tube drawing composite manufacturing process, the metal brush filaments are simultaneously drawn and annealed with the mandrel and metal tube, ensuring a secure connection between the metal brush filaments and the mandrel. This overcomes the problem of easy fiber shedding associated with flocking on the mandrel surface in existing technologies, ensuring the stability of the instrument during surgery and its effectiveness.

[0028] The composite embryo of the present invention has a simple manufacturing process, and the inner and outer materials can be flexibly combined. The metal tube and metal rod of the composite embryo can be made of different materials. While ensuring that the material of the file meets the surgical requirements, it does not affect the effect of use and facilitates cost control. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the hollow mandrel used in Example 1.

[0030] Figure 2 This is a schematic diagram of drilling holes in the mandrel in Example 1.

[0031] Figure 3 This is a schematic diagram of how a metal rod is made by inserting metal brush filaments into the hole of a mandrel in Example 1.

[0032] Figure 4 This is a schematic diagram of placing the metal rod into the metal tube in Example 1.

[0033] Figure 5 This is a schematic diagram of the composite embryo sectioning in Example 1.

[0034] Figure 6 This is a schematic diagram of the metal tube with the file body removed in Example 1.

[0035] Figure 7 This is a schematic diagram of the metal brush filaments in Example 1, where the free ends of the filaments open outwards to form the shape of roller brush filaments.

[0036] Figure 8 This is a schematic diagram of the processed handle in Example 1.

[0037] Figure 9 This is a schematic diagram of the file body being made into an inverted cone shape in Example 1.

[0038] Figure 10 This is a schematic diagram of multiple layers of metal tubing nested outside the mandrel in Example 2.

[0039] Figure 11 This is a schematic diagram of placing the metal rod into the metal tube in Example 2.

[0040] Figure 12 This is a schematic diagram of the composite embryo sectioning in Example 2.

[0041] Figure 13 This is a schematic diagram of the metal tube with the file removed in Example 2.

[0042] Figure 14 This is a schematic diagram of cutting the pipe into thin strips connected by rings in Example 2.

[0043] Figure 15 This is a schematic diagram of the shaping and fabrication of metal brush filaments with their free ends opening outwards, as shown in Example 2.

[0044] Figure 16 This is a schematic diagram of embodiment 3 showing metal brush filaments extending in the same direction embedded inside the ring.

[0045] Figure 17 This is a schematic diagram of placing the metal rod into the metal tube in Example 3.

[0046] Figure 18 This is a schematic diagram of the metal tube with the file removed in Example 3.

[0047] Figure 19 This is a schematic diagram of the processed handle in Example 3.

[0048] Figure 20 In Example 3, the metal brush filaments are made into a shape with the free end opening outwards.

[0049] Figure 21 This is a schematic diagram of metal brushes with different extension directions embedded inside the ring in Example 4.

[0050] Figure 22 In Example 4, the metal brush filaments are made into a shape with the free end opening outwards. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0052] Example 1:

[0053] The present invention discloses a three-dimensional self-adjusting root canal file with metal bristles, the manufacturing process of which includes the following steps:

[0054] S1. Fabricate a metal rod 2 with metal filaments on its outer surface; drill holes in the hollow core rod and insert the filaments; such as... Figure 1 As shown, fabricate a hollow mandrel 21; as... Figure 2 As shown, a hole 22 is drilled in the mandrel 21; as Figure 3 As shown, 3-30 metal brush filaments 23 are inserted into each hole to form a metal rod 2; in this embodiment, holes are preferably drilled symmetrically on both sides along the axis of the hollow core rod 21.

[0055] S2 fabricates a composite preform, which includes a metal tube 1 and a metal rod 2, with the metal tube 1 forming a dense enclosure around the metal rod 2.

[0056] S2.1 as Figure 4 As shown, metal rod 2 is placed inside the hollow structure of metal tube 1, and the cross-sectional shape of metal rod 2 is adapted to the cross-sectional shape of the hollow structure.

[0057] S2.2 The composite of metal tube 1 and metal rod 2 is drawn as a whole and annealed multiple times. The annealing temperature is 600-900℃, preferably 700-800℃. After drawing, the metal tube 1 tightly wraps the metal rod 2 inside it, thereby forming a dense and stable connection structure between the metal tube 1 and the metal rod 2.

[0058] S2.3 The composite of metal tube 1 and metal rod 2 is cold-drawn until its diameter is slightly larger than or equal to the diameter of the handle required for the root canal file, forming a composite blank; the cold drawing deformation is 20%-50%, preferably 30%-40%;

[0059] S3 as Figure 5 As shown, a composite embryo with a length greater than or equal to that of the finished root canal file is cut; as... Figure 6 As shown, the composite blank is divided into two parts: a handle 3 and a file 4. The outer metal tube 1, except for the handle 3, is removed by grinding or chemical methods, exposing the internal metal rod 2. Figure 6 As shown, the metal bristles 23 are attached to the outer surface of the mandrel 21 in a close-fitting state; as Figure 7 As shown, the metal brush bristles 23 are shaped so that the free ends of the metal brush bristles 23 open outwards, forming a roller brush bristle state.

[0060] S4 Figure 8 As shown, handle 3 is processed by chemical or grinding methods;

[0061] S5 Figure 9 As shown, the appearance of file 4 is processed into an inverted cone shape by grinding, shearing or chemical treatment.

[0062] Specifically:

[0063] In S1.1 and S1.2, the hollow structure of the metal tube 1 can be processed by an EDM drilling machine, an EDM wire cutting machine, or an EDM forming machine. The material of the metal tube 1 can be nickel-titanium alloy, stainless steel, cobalt-chromium alloy, copper, etc. The material of the metal rod 2 can be nickel-titanium alloy, stainless steel, cobalt-chromium alloy, copper, etc.

[0064] In S3, depending on the length of the connecting rod, a portion of the outer metal tube of the operating part other than the working part can be removed, so that a layer of metal tube is attached to the outside of the inner metal rod, and the thickness of the metal tube attached to the metal rod is 0.05-0.4mm.

[0065] In this embodiment, the cross-section of the metal rod 2 is preferably circular, elliptical, or the same. The cross-sectional shape of the space inside the metal tube 1 matches the cross-sectional shape of the metal rod, so that a more stable and densely wrapped connection structure is formed between the metal tube and the metal rod.

[0066] Example 2:

[0067] The difference between this embodiment and Embodiment 1 is that the file body 4 with metal bristles on the outer surface is made by nesting multiple layers of tubing and then cutting and shaping it. Specific steps include:

[0068] S1 makes metal rod 2, as follows Figure 10 As shown, a metal rod 2 is made by nesting multiple layers of metal tubing 24 outside a core rod 21. In this embodiment, the tubing 24 is preferably 4-10 layers.

[0069] S2 fabricates a composite preform, which includes a metal tube 1 and a metal rod 2, with the metal tube 1 forming a dense enclosure around the metal rod 2.

[0070] S2.1 as Figure 11As shown, metal rod 2 is placed inside the hollow structure of metal tube 1, and the cross-sectional shape of metal rod 2 is adapted to the cross-sectional shape of the hollow structure.

[0071] S2.2 The composite of metal tube 1 and metal rod 2 is drawn as a whole and annealed multiple times. The annealing temperature is 600-900℃, preferably 700-800℃. After drawing, the metal tube 1 tightly wraps the metal rod 2 inside it, thereby forming a dense and stable connection structure between the metal tube 1 and the metal rod 2.

[0072] S2.3 The composite of metal tube 1 and metal rod 2 is cold-drawn until its diameter is slightly larger than or equal to the diameter of the handle required for the root canal file, forming a composite blank; the cold drawing deformation is 20%-50%, preferably 30%-40%;

[0073] S3 as Figure 12 As shown, a composite embryo with a length greater than or equal to that of the finished root canal file is cut; as... Figure 13 As shown, the composite blank is divided into two parts: handle 3 and file 4. The outer metal tube 1 of the parts other than handle 3 is removed by grinding or chemical means to expose the inner metal rod 2.

[0074] S4 Figure 14 As shown, except for the innermost core rod 21, the tube 24 is cut into multiple rings 25 in the circumferential direction by laser or grinding. The part of the ring 25 away from the handle 3 is cut into thin strips in the axial direction.

[0075] S5 Figure 15 As shown, the slender strip is shaped to form a metal brush filament 26 with one end connected to the ring 25 and the free end opening outward.

[0076] In this embodiment, the shaping process adopts heat shaping, and the shaping temperature is 450-600℃, preferably 500-550℃.

[0077] Example 3:

[0078] The difference between this embodiment and Embodiment 1 is that the metal rod 2 with metal brush filaments on its outer surface is manufactured by setting a circular wire plug. Specific steps include:

[0079] S1 makes metal rod 2, as follows Figure 16 As shown, multiple rings 27 are spaced apart on the outer surface of a core rod 21, and metal brush filaments 28 are arranged circumferentially between the rings 27 and the core rod 21; the free ends of the metal brush filaments 28 extend beyond the rings 27, and the metal brush filaments 28 on each ring 27 extend in the same direction.

[0080] S2 fabricates a composite preform, which includes a metal tube 1 and a metal rod 2, with the metal tube 1 forming a dense enclosure around the metal rod 2.

[0081] S2.1 as Figure 17 As shown, metal rod 2 is placed inside the hollow structure of metal tube 1, and the cross-sectional shape of metal rod 2 is adapted to the cross-sectional shape of the hollow structure.

[0082] S2.2 The composite of metal tube 1 and metal rod 2 is integrally drawn and annealed multiple times. The annealing temperature is 600-900°C, preferably 700-800°C. After drawing, the metal tube 1 tightly wraps the metal rod 2 inside it, thereby forming a dense and stable connection structure between the metal tube 1 and the metal rod 2.

[0083] S2.3 The composite of metal tube 1 and metal rod 2 is cold-drawn until its diameter is slightly larger than or equal to the diameter of the handle required for the root canal file, forming a composite blank; the cold drawing deformation is 20%-50%, preferably 30%-40%;

[0084] S3 cuts a composite embryo with a length greater than or equal to that of the finished root canal file; such as Figure 18 As shown, the composite blank is divided into two parts: handle 3 and file 4. The outer metal tube 1 of the parts other than handle 3 is removed by grinding or chemical means to expose the inner metal rod 2.

[0085] S4 Figure 19 As shown, handle 3 is processed by chemical or grinding methods;

[0086] S5 Figure 20 As shown, the metal brush filaments 28 attached to the outer surface of the core rod 21 are shaped to become metal brush filaments with their free ends opening outwards in the form of roller brush filaments.

[0087] In this embodiment, the shaping process adopts heat shaping, and the shaping temperature is 450-600℃, preferably 500-550℃.

[0088] Example 4:

[0089] The difference between this embodiment and Embodiment 3 is that the extension directions of the metal brush filaments 28 disposed on the same ring 27 are different. Specific steps include:

[0090] In step S1, as Figure 21 As shown, multiple rings 27 are spaced apart on the outer surface of a core rod 21, and metal brush filaments 28 are arranged circumferentially between the rings 27 and the core rod 21; the free ends of the metal brush filaments 28 extend beyond the rings 27, and the metal brush filaments 28 on each ring 27 extend in different directions.

[0091] In this preferred embodiment, the ring 27 extends outward to form a near semi-circular ring 271 close to the handle 3 and a far semi-circular ring 272 away from the handle 3, wherein the metal brush filaments 28 on the near semi-circular ring 271 extend toward the handle 3, and the metal brush filaments 28 on the far semi-circular ring 272 extend toward the far handle 3.

[0092] In step S5, as Figure 22 As shown, the metal brush filaments 28 attached to the outer surface of the core rod 21 are shaped so that the free ends open outwards in the form of roller brush filaments.

[0093] It should be noted that the specific embodiments described above enable those skilled in the art to more fully understand the present invention, but do not limit the present invention in any way. Therefore, although the present invention has been described in detail with reference to the accompanying drawings and embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention. In short, all technical solutions and improvements that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the present invention patent.

Claims

1. A manufacturing process for a three-dimensional self-adjusting root canal file, comprising the following steps: S1 manufactures a metal rod, and then creates metal filaments on the surface of the core rod; S2 fabricates a composite preform, which includes a metal tube and a metal rod. The metal rod is placed in the metal tube and drawn and annealed in one piece, so that the metal tube forms a dense wrap around the metal rod. S3 cold-draws the composite embryo until its diameter is slightly larger than or equal to the maximum diameter of the root canal file. S4 divides the composite blank into two parts: a handle and a file; remove the outer metal tube of the file to expose the inner metal rod; S5 shapes the metal brush filaments on the metal rod; S6 processes the handle using chemical or grinding methods; the surface of the file is treated into a conical shape by grinding, shearing, or chemical methods.

2. The processing technology of a three-dimensional self-adjusting root canal file as described in claim 1, characterized in that: In step S1, the mandrel is a hollow tube, and holes are drilled in the mandrel to insert metal brush filaments into the holes; part of the metal brush filaments are inside the holes, and part of them are attached to the outer surface of the mandrel.

3. The processing technology of a three-dimensional self-adjusting root canal file as described in claim 1, characterized in that: In step S1, the metal rod is formed by nesting multiple layers of tubing outside the core rod. In step S4, in addition to the mandrel, the tube is cut into multiple rings along the circumferential direction, and a portion of the rings away from the handle is cut into thin strips along the axial direction.

4. The processing technology of a three-dimensional self-adjusting root canal file as described in claim 1, characterized in that: In step S1, multiple rings are spaced apart on the outer surface of the mandrel, and metal brush filaments are inserted between the rings and the mandrel; the free ends of the metal brush filaments extend beyond the rings. The metal bristles on each of the rings may extend in the same or different directions.

5. A three-dimensional self-adjusting root canal file manufactured using the process described in claim 1, characterized in that: It includes a metal tube and a metal rod, the inner surface shape of the metal tube matching the outer surface shape of the metal rod; the metal rod is placed inside the metal tube, and the metal tube forms a dense enclosure around the metal rod; the metal tube of the file body portion is removed, exposing the inner metal rod; the surface of the metal rod is provided with metal bristles with free ends opening outwards.

6. A three-dimensional self-adjusting root canal file manufactured using the process described in claim 2, characterized in that: It includes a metal tube and a metal rod, wherein the inner surface shape of the metal tube matches the outer surface shape of the metal rod; the metal rod is placed inside the metal tube, and the metal tube forms a dense enclosure around the metal rod; The metal tube of the root canal file is removed, exposing the internal metal rod. The metal rod is a hollow core rod with a hole, and one end of the metal bristles is inserted into the hole, while the other end opens outward to form metal bristles.

7. A three-dimensional self-adjusting root canal file manufactured using the process described in claim 3, characterized in that: It includes a metal tube and a metal rod, wherein the inner surface shape of the metal tube matches the outer surface shape of the metal rod; the metal rod is placed inside the metal tube, and the metal tube forms a dense enclosure around the metal rod; The metal tube of the root canal file is removed, exposing the internal metal rod. The core of the metal rod is surrounded by multiple layers of tubing, which is cut into multiple rings. The portion of the rings away from the handle is cut into thin strips. The free ends of the thin strips open outward to form metal bristles.

8. A three-dimensional self-adjusting root canal file manufactured using the process described in claim 4, characterized in that: It includes a metal tube and a metal rod, the inner surface shape of the metal tube matching the outer surface shape of the metal rod; the metal rod is placed inside the metal tube, and the metal tube forms a dense enclosure around the metal rod; the metal tube of the file body portion of the root canal file is removed, exposing the inner metal rod; multiple rings are spaced apart on the outer surface of the core of the metal rod, and metal bristles are inserted between the rings and the core; the free ends of the metal bristles extend beyond the rings.

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