JPH03231655A - Dental cutter and preparation thereof - Google Patents

Abstract

PURPOSE:To obtain stable cutting force and excellent durability by coating the cutting blade of a bar head made of a hard alloy or superfine particulate hard alloy having a blade groove with a diamond like carbon film. CONSTITUTION:A dental bar composed of a hard alloy or superfine particulate hard alloy having Knoop hardness of 1800 or more is used as a base material and a diamond like carbon film is formed to the surface of the cutting blade having a blade groove of the head thereof. The diamond like carbon film is formed in a gaseous atmosphere wherein the volume mixing ratio of hydrocarbon and hydrogen is 1:50-1:200 by a microwave plasma gaseous phase precipitation method. The hard alloy is a sintered body having a hard phase containing 3-6wt.% of cobalt as a metal phase and composed of WC or a mixture based on WC and containing one or more kind of carbide selected from carbides of Ti, Ta, V and Cr and the ultrafine particulate hard alloy is a sintered body wherein 3-6wt.% of Co is contained in one or more kind of carbide selected from carbides of W, Ti, Ta, V and Cr.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to improvements in dental cutting tools used for dental treatment or dental techniques.

(Prior art) Conventional dental cutting tools are made of iron-based alloy steel, cemented carbide, or ultrafine cemented carbide, and have cutting edges and grooves in their head A, as shown in Figure 1. A dental bur with a specific configuration is used. The material to be cut, the denture, has a high hardness of around 343 on the Knoop hardness scale, which is comparable to that of ordinary glass. This has the disadvantage of causing deterioration in cutting performance. Also used is a dental diamond point with a structure as shown in Figure 2, which has a ground surface on the head B made by strongly electrodepositing diamond powder on the surface of a metal base material using nickel or chrome plating. Although it is suitable for grinding objects with high hardness such as enamel, it is suitable for grinding softer denture with a Knoop hardness of around 68. This has the disadvantage that cutting performance deteriorates due to clogging. Continuing to use cutting tools with degraded cutting performance not only reduces work efficiency, but also
A large amount of frictional heat and minute vibrations are generated, and this heat generation causes discomfort and pain to the patient, and the minute vibrations may induce the occurrence of secondary caries.

Furthermore, with the recent spread of high-speed rotating handpieces that use air turbines and air bearings, dental cutting tools have come to be required to be even more durable. (Problems to be Solved by the Invention) The present invention aims to provide a dental cutting tool that has stable cutting performance from beginning to end, regardless of the hardness of the object to be cut, and has excellent durability.

(Means for Solving the Problems) In order to solve these problems, the present inventors conducted various studies on the material and manufacturing method of cutting blades, and found that they have high hardness,
The diamond-like carbon film is also non-toxic to the human body.
By coating the cutting blade of the head of a bar made of cemented carbide or ultrafine grained cemented carbide having a blade groove, stable cutting performance was successfully obtained regardless of the location of the denture, and the present invention was completed. Ta.

That is, the present invention relates to an improved dental bur made of cemented carbide or ultrafine cemented carbide and a method for manufacturing the same.

This uses a dental bur made of cemented carbide or ultrafine grained cemented carbide with a Knoop hardness of i, goo or higher as the base material, and a diamond-like carbon film is formed on the surface of the cutting blade with a groove on the head. A dental cutting tool characterized by: and a mixed gas having a volumetric mixing ratio of hydrocarbon gas to hydrogen of 1=50 to 1:200 when forming a diamond-like carbon film by microwave plasma vapor deposition method. The gist of this paper is a method for manufacturing a dental cutting tool, which is characterized in that it is carried out in an atmosphere.

The present invention will be explained in detail below.

The base material of the dental cutting tool of the present invention has a Knoop hardness of 1
, 800 or more cemented carbide or ultrafine cemented carbide powder is pressed into a rod-like shape similar to that shown in Figure 1, which does not have a cutting edge or groove on the head, and is sintered using a dental bur. . In the case of a cemented carbide, this alloy composition is composed of WC or WC as a main component and a hard phase containing 3 to 6% by weight of cobalt as a metal phase, and Ti, Ta, ■ and Cr.
It is a sintered body containing one or more of the metal carbides of W, Ti, Ta, V, and Cr in ultrafine particle cemented carbide containing 3 to 6% by weight of CO. It is a sintered body. If the amount of Go contained in this base material is less than 3% by weight, the toughness will decrease and the cutting edge will be more likely to break. If it exceeds 6% by weight, diamond-like carbon formed on the surface of the cutting blade will The film easily peels off during cutting, and cannot fully demonstrate its performance as a hard protective film. Therefore, the amount of Co is 3 to 6% by weight,
Preferably it is 4 to 5% by weight. If the Knoop hardness of these base alloys is less than 1,800, the diamond-like carbon film on the surface will peel off during cutting due to the difference in hardness. Therefore, the hardness of the base material should be 1,800 or more, preferably as high as possible.

Such Knoop hardness is 1,800 or more and CO is 3~3
A dental bar made of a cemented carbide containing 6% by weight or an ultrafine particle cemented carbide sintered body may be produced by a known method for producing a cemented carbide or an ultrafine particle cemented carbide sintered body. A predetermined amount of C is added to the alloy or ultrafine cemented carbide powder.
o powder, an organic solvent, paraffin, etc. are mixed, this is press-molded into the shape of a dental bar, pre-sintered in a hydrogen stream at 800 to 1000°C, and cutting edges and grooves are formed by grinding. Finally, main sintering is performed at a temperature of 1.350 to 1,550°C to produce a dental bar.

The greatest feature of the present invention is that the surface of the Co-containing cemented carbide or ultrafine-grained cemented carbide cutting blade is coated with a diamond-like carbon film to maintain the durability of cutting forces for a long period of time, regardless of the material to be cut. That's what happened. This diamond-like carbon film may be formed by the microwave plasma vapor deposition method, which is a known method, but film forming conditions suitable for the present invention include using a hydrocarbon gas such as methane, ethane, or propane as the carbon source; Uses a gas mixture with hydrogen gas. The volume ratio of this mixed gas is preferably hydrocarbon gas:hydrogen=1:50 to 1:200. If this hydrocarbon gas/hydrogen ratio is less than 1/200, the crystal grain agglomerates that make up the deposited diamond-like carbon film will become coarser, and the peel strength of the formed diamond-like carbon film will decrease. On the other hand, if it exceeds 1750, graphite components will become noticeable in the formed diamond film, making it impossible to obtain a film hardness sufficient to improve durability during cutting.

This microwave vapor phase plasma deposition method is carried out using an apparatus as shown in FIG. An unprocessed dental bur 1 is placed on the substrate support 2 inside the quartz glass reactor 3 of this device (only the head is exposed to microwaves,
(shade part must be covered), then heat the inside of the vessel with 1 x l low G~I
The pressure is reduced to a range of 10-'' Torr using the vacuum pump 5. Next, hydrocarbon gas and hydrogen gas in the ratios described above are introduced into the reactor from the respective cylinders 1O111 and are allowed to flow while being mixed.Reaction. The pressure inside the reactor greatly affects the temperature of the bar in the reactor and the morphology of the diamond-like carbon film formed, but in the present invention, the pressure within the reactor is 15 to 10.
It is preferable to adjust the pressure to a range of 0 Torr using the pressure regulating valve 6. Next, magnetron oscillator 1
A microwave with a frequency of 2.45 GHz that has been oscillated from the microwave 3 and propagated through the 2.45 GH2 rectangular waveguide 12 and a reflected wave of the microwave that has been reflected by the microwave reflector 4 flows in the reactor. A plasma flame is generated by absorption in the gas mixture.

This microwave reflecting plate 4 is located at the rear of the reactor at 2.45GH
It can be moved within a range of about 7 cm in the Z-shaped waveguide, and the position of the plasma flame generated around the bar can be adjusted. In addition, the impedance matching stub 7 is designed to effectively absorb microwaves into the mixed gas.
It is a metal rod inserted into the Z-type waveguide, and its insertion depth is varied by the automatic impedance matching device 8. The surface temperature of this bar is 800~1.100℃
Adjust the microphone wave high frequency power so that If the temperature of the bar is less than 800°C, the formation of a diamond-like carbon film will be slow, and if the temperature is about 1,100°C or higher, the mixing of graphite components into the formed diamond film will become noticeable. is 800~1,10
The temperature is preferably in the range of 0°C. Under the reaction conditions described above, hydrocarbon gas is thermally decomposed by a plasma mainly composed of hydrogen gas, and a uniform diamond-like carbon film is formed on the head of the bar. Although the present invention will be specifically explained by giving examples, the present invention is not limited thereto.

(Examples 1 to 4, Comparative Examples 1 to 6) Using WC cemented carbide with a Co content as shown in Table 1, straight handpiece 6 of JIS standard T5201 was used.
A dental bur (Fig. 1) having a single-blade shape was prepared.

Next, this bar is installed in the reactor, and the O, 0I inside the reactor is
After reducing the pressure to Torr, the mixed gas with the volume ratio of hydrocarbon gas and hydrogen gas adjusted to the ratio shown in Table 1 was heated to 100 Torr.
The pressure inside the system was maintained at 30 Torr while being introduced and circulated into the system at a flow rate of cc/min. In this atmosphere, microwaves with a frequency of 2.45 GH oscillated from the magnetron were guided into the reactor to generate a plasma flame around the bar, and the oscillation output of the magnetron was adjusted so that the temperature of the bar was 850°C. The reaction was allowed to proceed for a period of time to form a diamond-like carbon film. Regarding the dental cutting tool obtained as described above, JIS T5201
Similar to the side edge cutting test, two consecutive cutting tests were conducted, and the time required for cutting and the condition of the blade surface after cutting were examined to determine the durability test.

[Cutting test conditions] Work material: near acrylic plate (plate thickness 1 mm), cutting speed: 20
0Or, p, m, Side blade cutting distance: 10 mm each for both the 1st and 2nd cutting, Cutting load: 0° 5 kgf.

The test results are shown in Table 1. This shows that the dental cutting tool according to the present invention completed cutting within 20 seconds in both cutting tests. Furthermore, it is clear that the dental cutting tool according to the present invention has more stable cutting force and durability than Comparative Example 4, which is a conventional dental cutting tool.

(Effects of the Invention) According to the present invention, a dental cutting tool having more stable cutting force and superior durability than conventional ones can be obtained, and its utility value in the medical industry is extremely high.

[Brief explanation of drawings]

FIG. 1 is a side view of a dental bur having a cutting edge and a cutting groove, and FIG. 2 is a side view of a diamond point. Third
The figure is a conceptual diagram of a microwave plasma vapor deposition reaction apparatus. The main symbols are as follows. A, B... ・Dental bur head (cutting blade and blade groove) ・Dental diamond point head (grinding surface) ・Dental bur 2... Base material support base ・Reaction tube 4... Reflector plate・Vacuum pump 6...Pressure adjustment valve ・Stub for impedance matching ・Automatic impedance matching device ・Flow rate adjustment valve ・Hydrocarbon gas cylinder ・Hydrogen gas cylinder ・2.45GHz square waveguide ・ 3 ・ 5 ・ 7 ・8 ・ 9 ・ lO ・ 11 ・ 12 ・ Table 13 ・ ・Magnetron oscillator

Claims (1)

[Claims] 1. A dental bur made of cemented carbide or ultra-fine grained cemented carbide with a Knoop hardness of 1,800 or more is used as a base material, and a diamond-shaped cutting edge is formed on the surface of the cutting blade having a cutting groove on the head. A dental cutting tool characterized by forming a carbon film. 2. Cemented carbide or ultrafine grained cemented carbide contains 3 to 30% cobalt.
The dental cutting tool according to claim 1, comprising a metal carbide sintered body containing 6% by weight. 3. A dental clinic characterized in that the diamond-like carbon film is formed by microwave plasma vapor deposition in a mixed gas atmosphere in which the volumetric mixing ratio of hydrocarbon gas to hydrogen is 1:50 to 1:200. Manufacturing method for cutting tools.