JPH04224743A - Dental bur and its manufacturing method - Google Patents

Abstract

PURPOSE:To improve the life while preventing early dropping of an internal tissue from a base metal of grits by using the base metal formed into a long fiber in a direction of an axis line of rotation of the base metal. CONSTITUTION:Internal tissue of a tapered part 22 of a base metal 2 is formed into a fiber extending in a direction of an axis line of rotation of the base metal 2. As a result, the surface of the tapered part 22 has numerous crystal grains lengthened finely exposed in a circumferential direction of the tapered part 22. In addition, as the width of inert crystal grains exposed to the surface of a plated layer 3 is narrowed, the plated layer 3 formed on the inert crystal grains has coupling condition with the tapered part 22 reinforced by a plated layer 3 formed on active crystal grains located on both sides of the inert crystal grains.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dental bur used for cutting teeth or crowns, and a manufacturing method suitable for manufacturing the same.

0002

[Prior Art] Generally, dental burs are made by forming a metal plating layer such as nickel on the outer peripheral surface of the tip of a thin bar-shaped base metal, and using this plating layer, abrasive grains are fixed to the base metal. In use, the base metal is rotated at high speed (approximately 20,000 to 40,000 revolutions/second) and the blade portion with abrasive grains is pressed into contact with the teeth, etc., and the abrasive grains scrape the desired area. ing. In this case, a large cutting force acts on the abrasive grains. In order to prevent the abrasive grains from falling off the base metal due to this cutting force, it is necessary to firmly fix the abrasive grains to the base metal.

0003

However, in conventional dental burs, the abrasive grains fall off from the base metal relatively easily, resulting in a short service life.

When the cause of this problem was investigated, it was found that the cause lies in the internal structure of the base metal. That is, the base metal of the dental bar is made of martensitic stainless steel wire, and is formed into a desired shape and dimension by drawing, grinding, cutting, etc. the steel wire. After that, it is manufactured by quenching and tempering. The internal structure of the base metal manufactured in this way is mainly composed of relatively large crystal grains, as shown in Fig. 3, and each crystal grain contains crystal grains (hereinafter referred to as , active crystal grains) and crystal grains with low bonding strength (hereinafter referred to as inactive crystal grains). Since the inert crystal grains have a low bonding strength with the nickel plating layer, the nickel plating layer formed thereon peels off and falls off relatively easily. In particular, the nickel plating layer located at the center of the inactive crystal grains is separated from the active crystal grains, so the bonding strength is low, and the layer peels off from there. When the plating layer on the inactive crystal grains falls off, the plating layer on the active crystal grains also gradually falls off. As a result, the abrasive grains fall off the base metal prematurely, resulting in a shortened lifespan of the dental bur.

The present invention was made to solve the above problem, and provides a dental bur that can prevent the abrasive grains from falling off the base metal at an early stage, thereby improving the life of the dental bur. Another object of the present invention is to provide a manufacturing method suitable for manufacturing such a dental bur.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the dental bur of the present invention has a metal plating layer formed on the tip of the base metal in the shape of a thin rod, and the metal plating layer forms a metal plating layer on the base metal. The dental bur has abrasive grains fixed to the base metal, and is characterized in that the base metal has an internal structure in the form of fibers extending in the direction of the axis of rotation of the base metal. Further, the manufacturing method of the present invention includes a base metal manufacturing process, and an electrodeposition process of forming a metal plating layer on the base metal manufactured in this base metal manufacturing process and fixing abrasive grains to the base metal with this plating layer. In the method for manufacturing a dental bur, the base metal manufacturing process uses a work-hardening austenitic stainless steel wire as the base metal material, and draws the steel wire to form an internal structure. It is characterized by making it into a fiber shape and finishing it into a base metal while maintaining the fiber-like internal structure.

[0007]

[Operation] In the dental bur of the present invention, since the internal tissue is in the form of long fibers in the direction of the axis of rotation,
Both the active crystal grains and the inactive crystal grains are extremely elongated, and both are distributed almost uniformly in the circumferential direction on the surface of the base metal. Therefore, the bonding strength to the metal plating layer on the surface of the base metal becomes uniform in the circumferential direction of the base metal, and there are no portions with low bonding strength. Therefore, peeling of the plating layer is prevented.

Furthermore, in the method for manufacturing a dental bur of the present invention, the material of the base metal is wire-drawn to have an internal structure in the form of fibers, and the base metal is finished in that state. Therefore, the abrasive grains are firmly fixed to the base metal by the metal plating layer.

[0009]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 and 2. First, the dental bur according to the present invention will be explained with reference to FIGS. 1(A), (B), and (C). Straight shank part 20 at the end
is formed, and a tapered neck part 21 is formed in the middle part.
is formed, and a tapered portion 22 with a small taper angle is formed at its tip. Note that the tapered portion 22 may be formed into a straight shaft shape or a spherical shape instead. Further, although the tip of the tapered portion 22 is formed in a hemispherical shape, it may be formed in a plane perpendicular to the axis of the tapered portion 22. Tapered part 22
As shown in FIG. 1(B), a plating layer 3 made of metal such as nickel is formed. A large number of abrasive grains 4 are supported in this plating layer 3 in a state where about 1/2 to 2/3 of them are buried, so that the abrasive grains 4 are supported by the base metal 2.
It is fixed to the tapered portion 22 of. Note that the portion to which the abrasive grains 4 are fixed is the blade portion 5.

The above structure is the same as that of the conventional dental bur, but in the dental bur 1 of the present invention, the internal structure of at least the tapered portion 22 of the base metal 2 is aligned in the direction of the rotational axis of the base metal 2, that is, in the longitudinal direction. It is made into a fiber shape that extends in the direction. Along with this, the surface of the tapered portion 22 is as shown in FIG. 1(C).
It is shown in the figure below. That is, FIG. 1(C) shows a state in which the surface of the tapered portion 22 is etched and observed under a microscope, and the surface of the tapered portion 22 has a large number of crystal grains that are extremely elongated in the form of fibers. They are exposed along the circumferential direction of the tapered portion 22. In this case, the crystal grains include inert crystal grains with low bond strength with nickel,
Although there are active crystal grains with high bonding strength, both are distributed almost uniformly in the circumferential direction of the tapered portion 22.

[0011] Also in the dental bur 1 having the above structure, the bonding strength of the portion of the plating layer 3 formed on the inert crystal grains to the tapered portion 22 is low. However, since the internal structure is fiber-like, the plating layer 3
Since the width of the inactive crystal grains exposed on the surface of The bonding state with the tapered portion 22 is reinforced by the plating layer 3 formed on the active crystal grains. therefore,
The bonding strength of the plating layer 3 formed on the inert crystal grains appears to be increased, and separation from the tapered portion 22 is prevented. Therefore, the abrasive grains 4 are prevented from falling off from the tapered portion 22, and the life of the dental bur 1 is extended. Note that when forming a spherical part instead of the tapered part 22,
Active crystal grains and inactive crystal grains are exposed in dots on the surface. Of course, peeling of the plating layer 3 is also prevented in this case. Further, when the internal structure of the tapered portion 22 is fibrous, the strength of the tapered portion 22 is improved against forces acting in a direction perpendicular to the longitudinal direction of the tapered portion 22. Therefore, when grinding teeth, etc., the blade portion 5 can be strongly pressed against the teeth, thereby improving the grinding efficiency.

Next, a method for manufacturing the dental bur 1 according to the present invention will be explained with reference to FIG. The manufacturing method of the present invention can be roughly divided into a base metal manufacturing process 10 in which a base metal 2 is manufactured from a raw material, and an electrodeposition process 20 in which abrasive grains are fixed to the base metal 2 to form a dental bar 1.

First, the material will be explained. In the present invention, as the material of the base metal 2, an austenitic stainless steel wire rod having work hardenability is used. Conventionally, austenitic stainless steel does not have heat treatment hardenability, so if the base metal 2 is manufactured from austenitic stainless steel, the desired hardness and therefore the desired strength cannot be obtained. There was a problem. For this reason, austenitic stainless steel has not been used as the material for the base metal 2, but martensitic stainless steel having heat treatment hardenability has been used. However, in recent years, austenitic stainless steels with high work hardening properties have been developed, and it has been found that sufficient strength for the base metal 2 can be obtained by drawing and work hardening austenitic stainless steel wire rods. did. Therefore, an austenitic stainless steel wire is used as the material for the base metal 2. Note that examples of austenitic stainless steel include SUS304, SUS302, or SUS2.
01 etc. are used.

In this embodiment, the base metal manufacturing process 10 is subdivided into a wire drawing process 11, a centerless grinding process 12, and a turning process 13.

In the wire drawing step 11, wire drawing and annealing are usually repeated a plurality of times, and then a final wire drawing is performed. In the final wire drawing process, it is desirable that the ratio of the cross-sectional area of the material before processing to the cross-sectional area of the material after processing, that is, the area reduction rate, be 75% or more. SU containing an appropriate amount of elements that cause work hardening, such as carbon, etc.
The area reduction rate of austenitic stainless steel such as S304 is 7.
If wire drawing is applied to 5% or more, the hardness after processing will be HV60.
This is because it becomes 0 or more, and sufficient strength as the base metal 2 can be obtained. In addition, the final wire drawing process changes the internal structure of the material into a fiber-like structure. Note that processing by passing the material through one wire-drawing die once is referred to as one-time wire-drawing, but it is also possible to line up multiple wire-drawing dies and pass the material through each wire-drawing die in sequence. This is sometimes referred to as one-time wire drawing. In this case, annealing is performed every time the wire drawing process is performed multiple times. Furthermore, it is desirable to carry out the final drawing multiple times in order to make the internal structure of the material more fibrous.

In the centerless grinding step 12, the wire-drawn material is usually cut into a predetermined length, for example about 2 m, and then ground by a centerless grinder. In this case, the material is ground until its outer diameter becomes the diameter of the shank portion 20 of the base metal 2. Of course, centerless grinding of materials with a length of 2 m or more is sometimes performed.

In the turning process 13, the tip of the centerless-ground material is turned, and the taper part 22 and the neck part 21 are turned into predetermined dimensions and shapes in this order. Thereafter, the base metal 2 is obtained by cutting off a predetermined length from the tip of the material (the tip of the tapered portion 22). Of course, turning 13
In this case, the centerless ground material may be cut in advance to the length of the base metal 2, and then the neck portion 21 and the tapered portion 22 may be lathed in this order.

After manufacturing the base metal 2 as described above, an electrodeposition process 20 is performed. In the electrodeposition step 20, a plating layer 3 made of metal such as nickel is formed on the tapered portion 22, and the abrasive grains 4 are supported by this plating layer 3, thereby fixing the abrasive grains 4 to the tapered portion 22. , which is usually done as follows. That is, the tapered part 22 is inserted into a large number of abrasive grains 4 in a plating solution, so that the abrasive grains 4 are in contact with the tapered part 22. In this state, the metal to be plated is connected to the positive electrode of the power source, and the base metal 2 is connected to the negative electrode of the power source. Then, the plating layer 3 is formed on the tapered part 22.
is formed, and 1/2 to 2/3 of the abrasive grains 4 are buried in the plating layer 3, thereby fixing the abrasive grains 4 to the tapered portion 22. Note that before fixing the abrasive grains 4, a thin metal plating layer with high bonding strength may be formed on the tapered portion 22, and the abrasive grains 4 may be fixed to the tapered portion 22 via this plating layer.

As described above, in the manufacturing method of the present invention, when manufacturing the base metal 2, the internal structure of the material remains in the fiber form through wire drawing without performing heat treatment such as hardening in the final process. Finishing the base metal 2. Therefore, according to this manufacturing method, a long service life can be achieved by preventing the abrasive grains 4 from falling off early, and since the fibrous structure extends in the direction of the rotational axis of the base metal 2, the dental bar has high bending strength. 1 can be manufactured. Furthermore, since no hardening is performed, the base metal 2 can be prevented from warping or bending due to the hardening, and therefore a dental bur 1 with less rotational deflection can be manufactured.

[0020]

[Effects of the Invention] As explained above, according to the dental bur of the present invention, since the base metal has a fiber-like internal structure, it is possible to prevent the metal plating layer from peeling off. It is possible to prevent early falling off of the abrasive grains, thereby improving the service life, and the strength is high, so that effects such as being able to improve grinding efficiency can be obtained.

Furthermore, according to the method of manufacturing a dental bur of the present invention, the material of the base metal is wire-drawn to make its internal structure fiber-like, and the base metal is finished in that state. It is possible to produce a dental bur that has a long life, high strength, and less rotational deflection.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the dental bur of the present invention, FIG. 1(A) is a side view thereof, and FIG.
FIG. 1C is an enlarged cross-sectional view taken along the line B-B of A), and is a diagram showing the surface condition of the tapered portion of the base metal.

FIG. 2 is a process diagram showing one embodiment of the method for manufacturing a dental bur of the present invention.

FIG. 3 is a diagram showing the surface condition of a base metal of a conventional dental bur.

[Explanation of symbols] 1 Dental bur 2 Base money 3 Metal plating layer 4 Abrasive grains 10 Base metal manufacturing process 11 Line drawing process 20 Electrodeposition process

Claims (2)

[Claims] 1. A dental bar in which a metal plating layer is formed on the tip of a base metal in the shape of a thin rod, and abrasive grains are fixed to the base metal by the metal plating layer, in which the internal structure of the base metal is fixed to the base metal. A dental bur characterized by using a base metal that is shaped like a long gold fiber in the direction of the rotational axis. [Claim 2] Through a base metal manufacturing process and an electrodeposition process in which a metal plating layer is formed on the base metal manufactured in this base metal manufacturing process, and the abrasive grains are fixed to the base metal by this plating layer, dental In a method for manufacturing a dental bur,
In the base metal manufacturing process, work-hardening austenitic stainless steel wire is used as the base metal material, this steel wire is drawn to have a fiber-like internal structure, and the base metal is manufactured while maintaining the fiber-like internal structure. A method for producing a dental bur characterized by a gold finish.