JP7418183B2 - Dental file and method for manufacturing dental file - Google Patents

Description

The present invention relates to a dental file that has excellent flexibility while ensuring rigidity at the tip, and a method for manufacturing such a dental file.

Reamers and files are examples of dental root canal cutting tools used for enlarging and cleaning root canals in dental treatment (see Patent Document 1). The reamer cuts the inside of the root canal by mainly rotating it, and the file cuts the inside of the root canal by rotating it or pushing or pulling it in the axial direction.

Conventional dental root canal cutting tools were made of stainless steel, but in recent years, tools made of nickel titanium, which has high elasticity and are suitable for treating complexly curved root canals, are sometimes used. Furthermore, as for power, not only manual types but also electric types connected to a dental handpiece (engine) are increasing. And by making it electric, it is possible to perform treatment quickly.

FIG. 5 is a plan view of a typical dental file. The dental file 100 shown here is used by being connected to a dental handpiece. This dental file 100 includes a working part 101 consisting of a spiral tapered cutting blade, a shaft 102 connected to the rear end of the working part 101, and a shaft 102 connected to the rear end of the shaft 102 and attached to a dental handpiece. It has a grip part 103.

The manufacturing method for such dental files is to first process the part that will become the working part from a thin wire using a centerless processing machine so that it has a constant taper ratio (for example, 2/100), and then There is a method that uses a groove grinder to form grooves that will become the cutting edges of the working part.

In addition, as another manufacturing method, as described in Patent Document 2, the cross section of the wire is ground into a tapered rectangle, etc., and then twisted to create a dental file having a desired working part. There is also. FIG. 6 is a diagram illustrating a wire grinding method. Grinding is performed by bringing the wire 21 into contact with the rotary grindstone 50 while holding it down with the pusher 55. At this time, by controlling the pusher 55, it is possible to grind by a desired amount. If the cross section is to be tapered to a rectangular shape, the wire rod 21 may be rotated 90 degrees or 180 degrees around the axis each time one surface is ground, and the grinding may be repeated.

A dental file manufactured by such a method is desired to have excellent flexibility since it is necessary to cut a complicatedly curved root canal. Therefore, we considered changing the cross-sectional shape of the tapered part from square to rectangular to reduce the moment of inertia. On the other hand, there is a problem that the rigidity of the tip portion is insufficient. On the other hand, there are cases where a calcified root canal is cut, and in that case, the taper ratio may be increased to increase the rigidity of the tip. However, there is a problem in that the flexibility of the shaft portion is impaired accordingly.

Patent No. 4247345 Patent No. 4247346

In view of these circumstances, an object of the present invention is to provide a dental file that has excellent flexibility while ensuring sufficient rigidity at the tip, and a method for manufacturing such a dental file.

The dental file of the present invention is a dental file having a tapered working part equipped with a blade for cutting a root canal, and the working part includes a tip having a constant taper rate and a main body connected from the tip. The cross-sectional shape of the tip and main body is a rectangle with two pairs of opposite sides parallel to each other, and the cross-sectional shape of the main body has a variable side ratio of the two pairs of opposite sides, with one opposite side being parallel to the other. It is assumed that the tip is located on a side surface having the same taper ratio as the tip, and the other opposite side is located on a side surface that has a slower taper rate than the tip.

Here, when the cross-sectional shape of the tip is square, the cross-sectional shape of the main body is a rectangle or a parallelogram with an acute angle, and when the cross-sectional shape of the tip is rhombic, the cross-sectional shape of the main body has an acute angle. It may be a parallelogram with Further, the tip portion may range from the tip of the working portion to a desired position of 1.0 mm or more and 5.0 mm or less.

Further, in the method for manufacturing a dental file of the present invention, the side surface of the wire is pressed by a first pusher metal and brought into contact with a rotary grindstone to be ground, thereby forming a first tapered part having a square or rhombic cross-sectional shape. In the forming process, the two opposing sides of the first tapered part are pressed against a rotating grindstone while being pressed with a second pusher that contacts only behind the desired position from the tip. and a step of grinding the side surface by the same amount to form a second tapered part.

Here, it is preferable that the desired position from the tip is a position 1.0 mm or more and 5.0 mm or less from the tip.

Further, regarding the second tapered part, a step of grinding other surfaces other than the two surfaces ground while pressing with the second pusher by bringing them into contact with a rotary grindstone while pressing with the second pusher, It is also possible to have the following.

According to the present invention, it is possible to provide a dental file having a working part that has both a tip part with high rigidity and a main body part with excellent flexibility.

It is a figure explaining the manufacturing method of the dental file of this invention. It is a figure explaining the grinding using a 1st pusher metal. It is a figure explaining grinding using a 2nd pusher metal. It is a figure explaining the cross-sectional shape of a tip part and a main part. It is a figure explaining the cross-sectional shape of the tip part and main body part of another Example. It is a figure explaining the cross-sectional shape of the tip part and main body part of another Example. It is a top view of a general dental file. It is a figure explaining the grinding method of a wire rod.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

First, the outline of the steps of the method for manufacturing a dental file will be explained. FIG. 1 is a diagram illustrating the method for manufacturing a dental file of the present invention. 1(a) to 1(c) show a plan view and a side view in each step, and FIG. 1(d) shows a plan view of a dental file. A first tapered portion 21a having a square cross-sectional shape as shown in FIG. 1(b) is formed on the round bar-shaped wire 21 shown in FIG. 1(a) using a rotating grindstone and a first presser. Further, regarding the first tapered portion 21a, the tip portion 12 in a desired range from the tip remains square in cross-sectional shape, and the main body portion 13 behind the desired position from the tip is one of the four sides of the square cross section. The side surfaces of the first tapered part 21a corresponding to the two sides of are ground using a rotary grindstone and a second presser to form a second tapered part 21b having a rectangular cross-sectional shape as shown in FIG. 1(c). form. Finally, the first tapered part 21a and the second tapered part 21b, which serve as working parts, are twisted to complete the dental file 10 as shown in FIG. 1(d). These steps will be explained in detail below.

First, a round rod-shaped wire 21 cut to a desired length is prepared (FIG. 1(a)). The material of this wire 21 is not particularly limited, and various metals such as steel, stainless steel, or nickel-titanium alloy can be used.

Next, the side surface of the wire rod 21 is ground using a pusher and a rotary grindstone. FIG. 2 is a diagram illustrating grinding using the first pusher. Tilt the first pusher 51 so that it has a constant taper ratio (for example, to a value X where the taper ratio of the diagonal line of the cross section after twisting is 3/100), and Grinding is performed by contacting the rotary grindstone 50 while pressing with the presser metal 51, thereby forming the first tapered portion 21a having a square cross-sectional shape and a constant taper ratio. Note that the taper rate is not limited to a certain value. Here, the rotary whetstone 50 is a disk-shaped whetstone whose outer peripheral surface is used as a grinding surface, and the diameter of the rotary whetstone 50 is much larger than the length of the first tapered part 21a of the wire 21. The ground surface can be regarded as a substantially linear surface, that is, a flat surface. Furthermore, by transferring the shape of the grindstone to the presser metal 51 before grinding, it is possible to grind the side surface of the wire rod 21 into a desired shape. In addition, in order to grind the wire 21 so that it becomes the first tapered part 21a having a square cross-sectional shape, the wire 21 is rotated 90 degrees or 180 degrees around the axis every time one side surface is ground. Four flat surfaces may be formed by repeating the grinding. Moreover, with such a grinding method, it is also possible to grind a plurality of wire rods 21 at once. Note that the rotation angle of the wire rod 21 is not limited to 90 degrees or 180 degrees, and by adjusting the rotation angle, it is also possible to form the cross-sectional shape of the first tapered portion 21a into a diamond shape or the like. In particular, if the cross-sectional shape is a rectangle with two sets of parallel sides, the balance is good.

Further, the two opposing sides of the first tapered portion 21a are similarly ground using another presser and a rotary grindstone to make the cross section rectangular (FIG. 1(c)). However, as described in the prior art section, if the entire length of the tapered portion is made into a rectangular cross-sectional shape, the flexibility will be increased, but the rigidity of the tip portion will be insufficient. Therefore, the tip section 12 should be defined as a desired position between 1.0 mm and 5.0 mm from the tip of the working part, and this tip section 12 should not be ground any further but should be left with a square or diamond cross-sectional shape. Make it. That is, assuming that the tapered part connected to the rear of the tip portion 12 is the main body portion 13, it is preferable to grind only the main body portion 13 so that the cross-sectional shape is rectangular.

FIG. 3 is a diagram illustrating grinding using the second pusher. The center of the pusher is the center CL of the rotary grindstone, and when grinding is performed using the first pusher 51, the tip 12 located ahead of the center of the pusher will also be ground. In this case, if a pusher having the same shape as the first pusher 51 is used for grinding, the cross-sectional shape of the tip portion 12 cannot be maintained in its original shape. Therefore, the second pusher 52 is shaped so that it does not contact the tip 12 but only contacts the main body 13 located behind the desired position from the tip. Specifically, the second pusher 52 is cut so that it does not contact the wire 21 in front of the center position CL of the rotary grindstone 50, and it is cut so that it does not contact the wire 21 only in the rear of the center position CL of the rotary grindstone 50. Shape so that they touch each other. Further, the second pusher 52 is transferred so as to form a taper ratio that is gentler than that of the first pusher 51 (for example, a value Y such that the taper ratio of the diagonal line of the cross section after twisting is 2/100). By using such a second presser metal 52, the cross-sectional shape of the second tapered portion 21b can be formed into a rectangular shape or the like.

After grinding one side surface of the first tapered part 21a in this way, the wire rod 21 is rotated 180 degrees around the axis and each opposing side surface is ground by the same amount, so that the cross-sectional shape is rectangular. A second tapered portion 21b can be formed (FIG. 1(c)). In other words, by pressing the wire 21 with the second pusher 52 and grinding the side surface of the first tapered part 21a, the first tapered part 21a remains as it is from the tip to the desired position, and the desired position is removed from the tip. The second tapered portion 21b may be formed at the rear of the position. Note that if the first tapered part 21a is ground not parallel to the side surface but slightly inclined, or if the first tapered part 21a has a rhombic cross-sectional shape, the cross-sectional shape of the second tapered part 21b will be becomes a parallelogram. In addition, since only two surfaces are ground in this type of grinding, the cross-sectional shape of the second tapered portion 21b is not a series of rectangles or parallelograms of similar shapes, but a rectangle whose side ratio varies depending on the cross-sectional position. or a parallelogram.

In the wire rod 21 thus produced, the first tapered part 21a has a square or rhomboid cross section, and the second tapered part 21b has a rectangular or parallelogram cross section. Since the second tapered part 21b is obtained by grinding the first tapered part 21a, the taper ratio is gentler than that of the first tapered part 21a, and its moment of inertia is also smaller, so it is flexible. This will improve your sexuality. However, since the first tapered portion 21a located on the tip side remains, rigidity near the tip can be ensured.

Finally, the dental file 10 in which the working part 11 is formed by twisting the wire 21 is completed (FIG. 1(d)). Here, a portion formed by twisting the first tapered portion 21a is referred to as the tip portion 12, and a portion formed by twisting the second tapered portion 21b is referred to as the main body portion 13. Strictly speaking, the cross-sectional shape is slightly deformed by twisting, but the amount of deformation is considered to be small. It is assumed that the cross-sectional shapes of 13 are the same.

FIG. 4 is a diagram illustrating the cross-sectional shapes of the tip portion and the main body portion. Moreover, FIGS. 5 and 6 are diagrams illustrating the cross-sectional shapes of the distal end portion and the main body portion of another embodiment. The distal end surface (AA cross section) of the working portion 11, the interface between the distal end portion 12 and the main body portion 13 (BB cross section), and the cross section of the main body portion 13 (CC cross section) are shown, respectively. Note that the circle indicated by the dotted line is the circumcircle of the first tapered portion 21a shown in FIG. 1(b). In addition, when the first tapered part 21a is a rhombus as shown in FIG. 6, the longer diagonal of the rhombus is the circumcircle whose diameter is the circumscribed circle. 4, the cross section of the tip 12 is square and the cross section of the main body 13 is rectangular, FIG. 5 shows the tip 12 has a square cross section and the main body 13 has a parallelogram cross section, and FIG. 6 shows the tip In this embodiment, the cross section of the main body 12 is a rhombus and the cross section of the main body 13 is a parallelogram. Note that the cross section of the main body portion 13 is shown in a shape obtained by grinding two horizontal sides of a rectangle using a second presser.

Here, since the two vertical sides of the main body part 13 are not ground, they are located on the side surfaces having the same taper ratio as the tip part 12. On the other hand, the two lateral sides of the main body part 13 are ground, so that they are located on the side surfaces having a gentler taper ratio than the tip part 13. That is, with the BB cross section as a boundary, one opposite side is located on a side surface having the same taper ratio as the tip 12, and the other opposite side is located on a side surface having a slower taper ratio than the tip 12. In this case, the side ratio of the two pairs of opposite sides varies depending on the cross-sectional position. In the main body part 13, all four corners of the rectangle or parallelogram are inside the circle, so it can be seen that the taper rate of the main body part 13 as a whole is slower than that of the tip part 12.

The dental file 10 manufactured through the above process has a tapered working part 11 equipped with a blade for cutting a root canal, and the working part 11 has a constant taper ratio. It consists of a tip 12 and a main body 13 connected from the tip 12, and the cross-sectional shapes of the tip 12 and the main body 13 are rectangular with two pairs of opposite sides parallel to each other, and the cross-sectional shape of the main body 13 is as follows. , the side ratio of the two sets of opposite sides varies, one opposite side is located on a side surface with the same taper ratio as the tip 12, and the other opposite side is located on a side surface with a slower taper ratio than the tip 12. Become something.

Here, regarding the flexibility of the main body portion 13, if it is too soft, problems will arise in operability and the like. Therefore, at the boundary position between the distal end part 12 and the main body part 13, the side ratio of the cross-sectional shape is approximately 1:1, and the length of the diagonal line is less than 1:2. The side ratio of the cross section at the boundary position with the shaft shall be a rectangle or parallelogram with a side ratio of 1:2 or less. By limiting in this manner, the cross-sectional shape of the main body portion 13 does not become too thin, so that it is possible to prevent the main body portion 13 from becoming too soft while providing flexibility. Note that the tip portion 12 extends from the tip of the working portion 11 to a desired position of 1.0 mm or more and 5.0 mm or less, but this depends on the balance between the rigidity of the tip portion 12 and the flexibility of the main body portion 13. , is determined by considering the side ratio of the main body portion 13, etc.

Such a dental file 10 has a working part 11 that has both a tip part 12 with high rigidity and a main body part 13 with excellent flexibility. In addition, the excellent effect of being able to follow a complicatedly curved root canal can be achieved.

Furthermore, two surfaces other than the surfaces ground while being pressed with the second pusher 52 may be further ground by being brought into contact with the rotary grindstone 50 while being pressed with the second pusher 52 . Even in this case, the taper ratio will change between the tip 12 and the main body 13, and even with this configuration, it is possible to have both the flexibility of the main body 13 and the high rigidity of the tip 12. becomes.

10 Dental file 11 Working part 12 Tip part 13 Main body part 21 Wire rod 21a First tapered part 21b Second tapered part 50 Rotary grindstone 51 First pusher 52 Second pusher

Claims (3)

Grinding the side surface of the wire by pressing it against a rotating grindstone while pressing it with a first pusher metal to form a first tapered part having a square or rhombic cross-sectional shape;
Using a second pusher that is cut so as not to come into contact with the wire in front of the center position of the rotary grindstone and is transferred to form a taper ratio that is gentler than that of the first pusher, Only the two opposing side surfaces of the first tapered part are brought into contact with the rotary whetstone while pressing behind the center position of the rotary whetstone with the second pusher, a step of forming a second tapered portion by grinding the same amount so as to have a taper ratio that is gentler than that of the tapered portion; and a step of twisting the first tapered portion and the second tapered portion. A method for manufacturing a dental file, comprising: 2. The method for manufacturing a dental file according to claim 1 , wherein the center position of the rotary grindstone is located at a distance of 1.0 mm or more and 5.0 mm or less from the tip. Before the step of applying the twisting process, other surfaces of the second tapered part other than the two surfaces ground while being pressed with the second pusher are further ground while being pressed with the second pusher. 3. The method for manufacturing a dental file according to claim 1 , further comprising the step of grinding the file by bringing it into contact with the rotating grindstone.

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