JPH08280714A - Dewaxing and predrying method of investment casting mold for dental lost wax casting method - Google Patents

Abstract

PURPOSE: To produce an investment casting mold without roughening the inside surface of an investment casting mold and reducing the strength of the casting mold and to obtain a casting having good adaptability by executing the removal of the investment casting mold and predrying of the investment casting mold prior to incineration of the wax. CONSTITUTION: Works formed by working a metallic material or ceramic material to an annular, box or planar shape are preheated to a high temp. and are brought into contact with or proximity to the investment casting mold after curing. Further, the dewaxing and predrying are executed by the heat retained in these works. As a result, the wax melts and flows outside the investment casting mold. The moisture evaporates rapidly as well.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to dewaxing and pre-drying in a lost wax casting method using an investment material, which is performed in a dental technique.

[0002]

2. Description of the Related Art Lost wax method is generally used for casting dental casting materials, and the wax pattern buried in a dental refractory investment material is heated up to around 800 ° C. in an electric furnace for wax incineration. Then incinerated. At this time, special dewaxing is rarely performed as a pre-process of wax incineration, and it is customary that the dewaxing is naturally performed in the furnace during the temperature rise.

Recently, the dental refractory investment material itself has been improved so that it can withstand a rapid temperature rise, so that it can be incinerated at any time for the purpose of shortening the incineration time of the wax, or if the temperature rise of the incinerator is completed, Due to the high efficiency of being able to add it to the furnace even if it is already incinerated, the wax pattern is directly put into an electric furnace kept at around 800 ° C. after being buried and cured, and then rapidly heated and incinerated.

[0004]

In the casting of dental casting materials by the lost wax method, the surface roughness of the buried mold after wax incineration is an important problem that is deeply related to the suitability of the casting. When the wax is incinerated at a temperature higher than room temperature, it is naturally dewaxed in the furnace during the temperature increase, so that the inner surface of the buried mold is not likely to be rough. However, in an investment mold of the type that is rapidly heated and incinerated, surface roughness of the investment material occurs due to rapid boiling of wax and evaporation of water contained in the investment mold.

If the wax is to be incinerated by rapid heating and is not dewaxed, the wax is rapidly heated by the high temperature in the furnace of about 800 ° C. and becomes in a violent boiling state. Further, the steam is blown out due to the rapid drying of the buried mold at the contact surface between the boiling wax and the buried mold material. These are the causes of roughening the inner surface of the buried mold and reducing the strength of the mold.

For this reason, it is desirable to heat the wax at a low temperature in advance before incineration to dewax and pre-dry the buried mold. However, in order to perform dewaxing and pre-drying before incineration, it is exclusive to incineration. A furnace is needed. However, this method takes much time and labor and is almost the same as the conventional method in which the temperature is raised from room temperature to incinerate the wax, so that it has not been carried out at present.

On the other hand, when the wax is incinerated in the lost wax method, a large amount of exhaust gas is generated due to the wax, and if the exhaust equipment is not perfect, the laboratory is polluted, which is a health problem for workers working there. . In particular, when a large amount of wax patterns are incinerated continuously, exhaust gas of the generated wax is exhausted to the outside of the room to prevent the inside of the laboratory from being polluted, and an exhaust gas treatment facility is required to prevent the air from being polluted.

Further, when a large amount of wax is incinerated at one time, the oxidized state of the atmosphere in the furnace cannot be sufficiently maintained, and it takes time to completely incinerate.

[0009]

SUMMARY OF THE INVENTION The present invention provides a method for dewaxing and predrying without the use of a dedicated electric furnace. That is, the present invention is a method for dewaxing and pre-drying a buried mold in a dental technique lost wax casting method that utilizes the retained heat of a metal material or a ceramic material heated to a high temperature.

The material of the metal material or ceramic material used in the present invention is not particularly limited as long as it can withstand a temperature of 800 ° C. Forged metal, cast steel, stainless steel, nickel steel, chrome steel, etc. can be used as the metal material, and alumina, magnesia, zirconia, mullite, etc. can be used as the ceramic material.

In the present invention, a metal material or ceramic material processed into a ring shape, a box shape, or a plate shape (hereinafter referred to as a processed product) is prepared, which is preheated to a high temperature to be buried and cured. Dewaxing and pre-drying are easily performed by the heat retained by these workpieces in contact with or in the vicinity of the buried mold. This melts the wax, flows out of the buried mold, and gently evaporates the water. The method of preheating this processed product is not particularly limited, but it is most convenient to put it in a wax incinerator kept at 800 ° C. to heat it.

The metal or ceramic work piece used in the present invention has a material, shape, and size that are large in consideration of the size of the buried mold used in the lost wax method and the amount of heat necessary for effective dewaxing. Can be decided At this time, if the heat capacity of the processed product is too large, the effect of preventing the surface roughness of the buried mold is halved, and the wax vaporizes to generate exhaust gas, which is not preferable. On the contrary, if the heat capacity of the processed product is too small, dewaxing and preliminary drying will be insufficient. This processed product can be repeatedly used.

[0013]

Function: The buried mold is heated rapidly at first because the workpiece heated to around 800 ° C comes into contact with or comes close to it, but the heat slightly reaches the center of the mold where the wax pattern is buried. Time is required. By using a work piece with an appropriate heat capacity, the temperature of the work piece is decreasing by the time the wax is heated and the dewaxing begins, and it can be dewaxed without overheating and dewaxing in a short time. Predrying can be completed.

When the workpiece is cooled and dewaxed and pre-dried, the buried mold is placed in a wax incinerator maintained at a temperature near 800 ° C. By doing so, the amount of wax incinerated in the wax incinerator becomes small, and the amount of exhaust gas generated can be greatly suppressed. Further, the wax can be recovered and reused by using a tray or the like for receiving the wax that has flowed out from the buried mold during the dewaxing.

[0015]

[Example] Inner diameter 30 mm, outer diameter 32 mm, height 40 mm
A wax pattern of the crown restoration was embedded in the ring for the buried mold using a phosphate refractory investment material and cured to obtain a buried mold. An outer surface of the buried mold was covered with a stainless steel ring having an inner diameter of 35 mm, a thickness of 3 mm and a height of 30 mm heated to 800 ° C., and dewaxing and preliminary drying were performed for 5 minutes. After this, the buried mold was placed in an electric furnace maintained at 800 ° C for 3
After incineration for 0 minutes and cooling, the inner surface of the buried mold was observed with a microscope. Also, the wax that had flowed out during dewaxing was collected in a tray and the amount thereof was measured. As a result, 8 without dewaxing
Roughness of the inner surface of the investment material mold was extremely small compared to the case where wax was incinerated by rapid heating at 00 ° C, and it was as smooth as when dewaxed by heating at a low temperature of 100 ° C for 30 minutes. It was In the method used, the wax flowed out in about 3 minutes, and about 80% of the buried wax was recovered.

Further, the crown restorations cast by using the buried mold produced by the method carried out are 80% without dewaxing treatment.
Compared with the crown restoration obtained by using the buried mold which was incinerated by rapid heating at 0 ° C, the compatibility was excellent and the casting surface was smooth.

[0017]

Industrial Applicability The present invention utilizes the conventional electric furnace for wax incineration and prepares the wax for dewaxing and the preparation of the buried mold only by separately preparing a work piece made of a metal material or a ceramic material which can be repeatedly used. By performing the drying, it is possible to manufacture the buried mold without roughening the inner surface of the buried mold or reducing the strength of the mold, and it is possible to obtain a cast product having good compatibility. Furthermore, according to the present invention, since the amount of wax incinerated in the wax incinerator is small, there is no concern about environmental pollution, and the wax can be recovered and reused.

Claims (1)

[Claims] 1. A method for dewaxing and pre-drying an embedded mold in a dental lost wax casting method, which utilizes the retained heat of a metal material or a ceramic material heated to a high temperature.