JPS6150454B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing H files for cutting dental root canals, and more specifically, in manufacturing H files (Hedström files) for cutting dental root canals. A method for manufacturing H-files, which comprises twisting a round wire rod for production in advance to the helix angle of the H-files, and then grinding the round wire rod to form the cutting edge of the H-files. It is related to.

There are mainly three types of dental root canal cutting tools: reamers, K-files, and H-files. Among these, the reamers and K-files have a certain small diameter as shown in Figure 1 A, B, C, and D. A round wire 1 that has been drawn and cut to a certain length is ground to a square or triangular shape, leaving the base part intact and the other middle part and tip part, and then twisting the ground part to form a cutting blade 2. The reamer or K-file was manufactured by forming a handle 3 and attaching a handle 3 to this base, but only the H-file was produced by rotating the round wire 1 as shown in Fig. 2 A, B, and C. The cutting edge 4 was formed by grinding the blade into a spiral shape, and the handle 3 was then attached to the base. There are not only H-files but also uni-files that perform spiral grinding, but the H-file will be explained below as a representative example. Therefore, H-files, Uni-files, etc. are collectively referred to as H-files.

On the other hand, the aforementioned round wire rod 1 was constructed by repeatedly passing a round bar of steel or austenitic stainless steel through a die and gradually making it thinner. In this case, the normal metal structure having solid crystal grains as shown in FIG. 3 had changed to a fibrous metal structure having linear crystal grains as shown in FIG. Especially SUS304
Since there is no hardening method such as quenching for austenitic stainless steels such as steels, wire drawing is performed many times without sintering to achieve sufficient work hardening, so the metal structure becomes more fibrous. It had been.

Therefore, there is no problem when forming a cutting edge by twisting the entire square or triangularly ground wire as in the case of the reamer and K-file described above, but if the cutting edge is formed by twisting the entire wire that has been ground into a square or triangular shape, as in the case of the H-file, when rotating a round wire When a cutting edge is formed by grinding the outer circumferential surface of a round wire rod in a direction intersecting the axis, the fibrous structure is cut one after another as shown in Figure 5, and as a result, the manufactured H file is It is weak against torsion, and when torsional force is applied during root canal cutting work, the cutting edge portion of the H file may break or break and be left behind in the root canal.

The method according to the present invention is a technology developed in view of the drawbacks of the conventional methods, and particularly relates to a completely new technology that makes it possible to prevent cutting of fibrous tissue when forming a cutting edge. .

To specifically explain one embodiment of the present invention with reference to the drawings, as shown in FIGS. 6A, B, C, and D, first, the base part of the round wire 1 is left, and the other intermediate part and tip part are twisted. The helix angle θ, which is the same as the torsion angle that the originally completed H file has, is formed in advance in this portion 5. At this time, if necessary, tempering treatment (heat treatment) is performed to stabilize the twisting process, and then The cutting edge 4 is formed by grinding the outer peripheral surface in a spiral shape approximately along the helix angle θ while rotating the twisted part 5, and further by attaching the handle 3 to the base part. H-files can be manufactured using the same method.

As described above, the method according to the present invention involves twisting a round wire in advance to form a helix that is equal to the helix angle that the H file originally has, and then twisting the helix approximately parallel to the helix angle while rotating the round wire. Since the cutting edge is formed by grinding the part, the fibrous tissue is not cut one after another as in the conventional method, but the cutting edge is formed by grinding parallel to the flow of the fibrous tissue, as shown in Fig. 7. Therefore, the H-file manufactured in this way is highly resistant to torsion, and has the characteristics that there is no risk of breakage or damage even if it is twisted considerably during torsional drilling during root canal cutting. . Regarding dental root canal cutting tools such as reamers, K-files, and H-files, the ADA and ISO standard drafts state that, for example, No. 20 (020) has a torsional torque.
Torsion standards are specified, such as 18 g-cm or more, and thread breakage occurs when the rotation is 540 degrees or more, but the H-file manufactured by the method of the present invention as described above has extremely better torsion torque and thread breakage than these standards. I was able to get the angle.

Furthermore, the cutting edge is stronger and less prone to sagging than conventional ones, resulting in a 1.3 to 1.7 times increase in the durability of the cutting edge.

[Brief explanation of the drawing]

FIGS. 1 and 2 are explanatory diagrams showing the manufacturing process of the cutting tool, FIGS. 3 and 4 are explanatory diagrams showing crystal grains of the metal structure, and FIG. 6 is an explanatory diagram showing the method of the present invention, FIG. 5 and FIG. 7 are explanatory diagrams showing the metal structure and the direction of the cutting edge. 1 is a round wire rod, 2 and 4 are cutting blades, 3 is a handle, and 5 is a twisted part.

Claims (1)

[Claims] 1. In the production of H-files for dental root canal cutting, the direction of the fiber-like crystal grains of the round wire is determined in advance by twisting the round wire for producing H-files at a certain angle. The cutting edge of the H files is formed by arranging the wire in a direction equal to the helix angle of the H files, and then grinding the outer circumferential surface of the round wire substantially parallel to the helix angle. Method of manufacturing files.