JPH11299809A - Method for adjusting the polymerization temperature of denture base resin - Google Patents

Abstract

(57) [Summary] [PROBLEMS] In a method of irradiating a resin for denture base filled in a gypsum mold with microwaves to polymerize the resin, using a microwave irradiator of a given output, resin thickness, etc. To obtain a good cured resin. SOLUTION: In a method of irradiating a microwave to a heat-curable resin charged in a gypsum mold to polymerize and cure the resin, the gypsum mold includes a sulfate, hydrochloride of a 1A, 2A, 1B, 7B or 8B group metal. Adding nitrate, phosphate, carbonate, carboxylate or borate, or carboxylic or boric acid to control the rate of temperature rise of the resin during microwave irradiation. By controlling the rate of temperature rise of the gypsum mold and the resin according to the present invention, the object can be achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a denture base resin,
Heat-curable resin such as silicone rubber is polymerized and cured to make a dental prosthesis for general dental prostheses, a mouth protector,
It relates to making epitheses, prostheses, etc. for splints, orthodontic floor devices and maxillofacial prostheses.

[0002]

2. Description of the Related Art In dental technics, a denture base is mainly made by charging a resin into a gypsum mold and heating the whole with hot water to polymerize the resin. On the other hand, from the advantages such as shortening of polymerization time, attempts have been made to polymerize by heating the resin by irradiating microwaves.

[0003]

However, using a microwave irradiation device of a given output that is easily available, when the thickness of the resin portion is large or when the thickness greatly varies depending on the position in the denture base, the method is suitable. It was difficult to obtain a cured resin. That is, there is a problem in that the surface hardness is insufficient and the presence of internal bubbles is present. For example, when a common microwave range of 500 W output is used, the resin portion has a thickness of 1.
When the thickness is 5 to 3 mm, a good cured product can be obtained by irradiation for 1.5 to 3 minutes.
When there is a change in the range, there is no irradiation time for obtaining a good cured product.

The present invention solves this problem.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a method for polymerizing and curing a resin by irradiating a microwave to a heat-curable resin charged in a gypsum mold.
A sulfate, hydrochloride, nitrate, phosphate, carbonate, carboxylate or borate of a metal of group A, 1B, 7B or 8B;
Alternatively, the method is characterized in that the rate of temperature rise of the resin during microwave irradiation is adjusted by adding carboxylic acid or boric acid.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the method of the present invention, gypsum is not particularly limited, and ordinary plaster, hard gypsum, super-hard gypsum and the like can be used. The mixing ratio of water and gypsum may be as usual, and for example, the weight ratio of ordinary gypsum may be 0.35 to 0.4. A feature of the present invention is to reduce the rate of temperature rise of the resin during microwave irradiation by including a salt of the above-mentioned metal or a carboxylic acid or boric acid or a salt thereof in a gypsum mold. For this purpose, the above compound is added to a mixture of gypsum and water,
The gypsum may be hardened. Salts containing Na, K, Ca, and B are preferable from the viewpoint of the effects of the invention and the effect on the human body.
In particular, NaCl, KCl, CaC added to the plaster mold
l ₂ , Na ₂ SO ₄ , and K ₂ SO ₄ have a remarkable effect of lowering the rate of temperature rise of the resin during microwave irradiation. 0.05% by weight or more, especially about 0.08 to
A remarkable effect can be obtained by adding 3.5% by weight of NaCl or the like. Therefore, when the temperature rises sharply, this can be suppressed, and a cured product having no bubbles and a good surface hardness can be obtained even in the center of the cured resin product.

[0007] Microwaves are characterized in that heat is concentrated at the center of an object to be heated. Therefore, the temperature of the object to be heated after the microwave irradiation is hard to be uniform.

In the case of dental technicians, when a denture base resin buried in a gypsum mold has a large thickness when a metal denture is manufactured,
After the microwave irradiation, the internal temperature of the central portion showed a sharp rise, and bubbles were generated in the middle of the resin portion. In addition, the resin portion near the gypsum mold had a problem that the temperature was low and the resin was not polymerized, and sufficient hardness could not be obtained.

On the other hand, in microwave irradiation of food and cooking,
When the concentration of salt exceeds a certain level, the amount of radio wave absorption increases as compared to water. However, in practice, a considerable amount of radio waves are absorbed near the surface, so that the number of radio waves reaching the inside decreases, and conversely, the temperature of the central part decreases. At the end, the absorption increased and the internal temperature increased. This method was applied to a gypsum mold for resin polymerization, and a method for averaging the internal temperature in the center of the resin part and in the vicinity of the mold was developed.

Resins for heat polymerization are known, and for example, (meth) acrylate resins can be used.

Hereinafter, the present invention will be further described by way of examples.

[0012]

EXAMPLES The gypsum used for the material was ordinary plaster (dental plaster, Swan Co., Ltd.). Akron No. 1 is a heat-polymerizable resin. 5. The clear ratio (GC) was used, and the mixing ratio (weight) of the polymer and the monomer was 2.4 to 1.

[0013] Distilled water was used as the kneading water, and a predetermined amount of the temperature raising rate controlling agent according to the present invention was dissolved in the distilled water, adjusted to 23 ± 1 ° C, and then mixed with gypsum. The weight ratio of water to gypsum is
It was set to 0.38. Table 1 shows the types and amounts (% by weight based on the gypsum raw material) of the heating rate controlling agent used. The symbol is
This is a symbol in a graph described later.

[0014]

[Table 1] For the metal floor, a Co-Cr alloy floor (Smalloy Cobalt, Shofusha) in a form assuming a maxillary complete denture is cast by an ordinary method,
Used after polishing.

The microwave irradiation range is manufactured by Hitachi, Ltd. and has a frequency of 2.45 GHz and an output of 500 W.
It is. During irradiation, the irradiation target was manually turned upside down every 30 seconds, and irradiation was performed alternately from above and below.

Preparation of Gypsum-Type Block for Measuring Temperature Rise Gypsum (2) is poured into the lower casing of a dental FRP flask (GC) (1), and the two positions (a, b) shown in FIG. ) Is 4.5 mm with two thermocouples (3a and 3b)
New gypsum mud was injected into the upper case part 60 minutes after the start of mixing of the lower case gypsum. This was left in a thermo-hygrostat (23 ± 1 ° C., RH50 ± 5%) for 2.0 hours. This was irradiated with microwaves, and the temperature rise was measured.
The measurement was performed on three gypsum blocks, and the average value was obtained.

Preparation of a mold for measuring the temperature rise of the resin part A 9 mm thick horseshoe-shaped wax prototype and an upper metal floor are buried with gypsum on the surface of the center of a dental FRP flask, and the mixing of gypsum begins. After 60 minutes, the gypsum separating material was applied to the gypsum surface. As shown in FIG. 2, thermocouples (3x and 3y) were inserted into the wax prototype at the center x corresponding to the front teeth and the center y corresponding to the last molars, and the upper casing was filled with gypsum. 6 from the start of the mixing of the plaster
0 minutes later, the thermocouple was exposed by flowing in a conventional manner, and left in a thermo-hygrostat (23 ± 1 ° C., RH50 ± 5%) for 1 hour. Pressure (20kgf / cm
^{After 2} ) and pressing (30 kgf / cm ² ), microwave irradiation was performed to measure the temperature rise. The experiment was repeated three times and averaged. In the figure, 2 is a gypsum, 4 is a metal floor resin part, 5 is a metal floor, and the dimensions are in mm.

Preparation of Test Specimen for Evaluation of Resin Cured Product A polymerized resin was obtained in the same manner as above except that no thermocouple was inserted. The flask is then brought to room temperature (23 ± 2
℃), then poured into water to cool, then opened, taken out of the cured resin together with the metal floor, and evaluated.

Surface hardness is durometer (type A)
It measured using. The five specimens were measured at five locations on the front and back surfaces respectively (a total of 10 locations), and the average value of the whole was taken. Warm water heating (70 ° C. × 30 minutes and 10
(0 ° C. × 30 minutes), the resin having a surface hardness of 90 or higher than that of the resin polymerized was judged to be acceptable.

A petri dish filled with water was placed on the lighted charkasten, the cured resin was immersed in the dish, and the presence or absence of internal bubbles was visually observed. Observation was made on five test specimens, and all of the specimens were evaluated as having no air bubbles, and rejected even with fine air bubbles.

When both the surface hardness and the presence / absence of air bubbles were acceptable, it was regarded as good.

Result A. 3 and 4 show gypsum molds containing 0.38 and 0.76 NaCl.
Or the temperature change of the central part (a) and the edge part (b) of the gypsum mold when 1.52 weight% is added is shown, respectively. The horizontal axis is the microwave irradiation time (minutes). Compared to the temperature change without NaCl (control: NON) (solid line), 0.76% of NaCl added (NA2) and 1.52
In the case of% addition (NA4), the rate of temperature rise in the central part is reduced. When 0.38% of NaCl was added (NA1), the difference from the control was not conspicuous. The temperature rise at the edge without NaCl was slower than that at the center without NaCl. The difference in temperature rise due to the addition of NaCl at the edge is smaller than that at the center.

B. Table 2 shows the temperature change in the resin parts x and y,
And that of the site x is shown in FIG.

[0024]

[Table 2] When a gypsum mold to which NaCl was added at 0.76% by weight or 1.52% by weight was used, a rapid rise in temperature inside the resin was suppressed. Table 2 also shows the number of experimental runs in which good resin cured products were obtained in terms of surface hardness and internal bubbles in 10 experiments (5 specimens each time). Under these experimental conditions, the irradiation time was 3 minutes when 0.76% of NaCl was added, and 3.5 minutes when 1.52% of NaCl was added. On the other hand, when NaCl was not added, only a good cured product of one specimen was obtained when the irradiation time was 2 minutes, and no good cured product was obtained at other irradiation times.

Next, the same experiment was conducted by adding other agents shown in Table 1 to the gypsum mold in the amounts shown in Table 1 in place of NaCl. 6 and 7 show the temperature change at the center of the gypsum mold. In each case, it can be seen that the temperature rise at the center is effectively reduced.

[0026]

According to the present invention, by adding a specific agent to a gypsum mold for polymerizing a denture base resin, it is possible to control the temperature rise of the resin during microwave irradiation, and to obtain a good resin cured product.

[Brief description of the drawings]

FIG. 1 is a plan view (a) and a cross-sectional view (b) of a gypsum mold showing a portion (a and b) of a thermocouple used for measuring a gypsum mold shape and a temperature rise of the gypsum mold.

FIG. 2 is a plan view of a gypsum mold showing a buried position (a shaded portion) of a resin part in contact with a metal floor in a gypsum mold and sites (x and y) of a thermocouple in a case of measuring a temperature rise of the resin part. (A) and cross-sectional view (b)

FIG. 3 is a graph showing a temperature rise at a central portion a in a gypsum mold during microwave irradiation according to the present invention (addition of sodium chloride). Horizontal axis: irradiation time (minutes) Vertical axis: temperature (° C.)

FIG. 4 is a graph showing a temperature rise at an edge b in the above.

FIG. 5 is a graph showing a temperature rise in a resin central part (x) in the above.

FIG. 6 In an embodiment using sodium sulfate,
Graph showing the temperature rise in the central part (a) in the plaster mold

FIG. 7 is a graph showing a temperature rise at a central portion (a) in a gypsum mold in an embodiment using potassium sulfate.

[Brief description of reference numerals]

 1: FRP flask 2: Gypsum 3: Thermocouple 4: Resin in contact with metal floor 5: Metal floor

Claims (3)

[Claims] 1. A method for irradiating a microwave to a heat-curable resin charged in a gypsum mold to polymerize and cure the resin, wherein the gypsum mold comprises a sulfate, a hydrochloric acid, or a hydrochloric acid of a Group 1A, 2A, 1B, 7B or 8B metal. A method comprising adjusting the rate of temperature rise of a resin during microwave irradiation by adding a salt, nitrate, phosphate, carbonate, carboxylate or borate, or carboxylic acid or boric acid. . 2. The material added to gypsum is sodium,
The method of claim 1 which is a potassium or calcium salt. 3. The method of claim 1 wherein the rate of temperature rise is reduced by adding sodium chloride or sodium sulfate.