JPH06687B2 - Denture base molding material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a molding die for molding a denture base using a thermoplastic resin.

[Prior Art and its Problems] Conventionally, most denture bases are made of acrylic polymer. It is formed by heating a mixture of an acrylic monomer and a polymer in a gypsum mold at room temperature or a relatively low temperature to polymerize the mixture.

When a denture base is compression-molded using a thermoplastic resin, in order to soften and deform the resin in the molding die,
It is necessary to raise the temperature to 350 ° C. Due to this temperature rise, the compressive strength of the gypsum mold is greatly reduced, and it cannot withstand the molding pressure and is damaged. Furthermore, since the water of crystallization is lost and the water shrinks violently, the compatibility of the denture base with the oral impression becomes poor.

Japanese Patent Application Laid-Open No. 59-195561 discloses that a mold made of a mixture of gypsum and silicon oxide does not cause reduction in compressive strength and shrinkage even when heated at 200 to 400 ° C. However, when cristobalite is used as the silicon oxide, it causes significant body expansion in the temperature range of 250 to 300 ° C. Therefore, the size of the mold varies depending on whether it is molded at 250 ° C. or lower and at 300 ° C. or higher. to differ greatly. Therefore, it is necessary to adjust the ratio of gypsum and cristobalite according to the softening temperature of the thermoplastic resin used. Further, when quartz is used as the silicon oxide, since its body expansion coefficient is small, the volume expansion of the mold cannot compensate for the volume decrease due to the thermal contraction of the thermoplastic resin at the time of temperature decrease, and the oral impression of the denture base is The compatibility is poor. In this case, if the concentration of colloidal silica is increased and the volume expansion of the mold is increased, the conformity to the oral impression is improved, but there is a new problem that the mold is cracked by heating.

Furthermore, when gypsum and cristobalite are mixed, the components may be separated due to vibration or the like because the specific gravities of the two are quite different.

[Means for Solving Problems] The present invention relates to a molding die that can easily mold a denture base excellent in adaptability to an oral impression using a thermoplastic resin.

The present invention is 30-70 wt% gypsum and 70-30 wt%
The present invention relates to a denture base molding material made of a thermoplastic resin in which 18 to 40 parts by weight of colloidal silica is mixed with 100 parts by weight of a mixture of calcium carbonate.

The mold of the present invention does not excessively shrink due to heating, and also maintains high compressive strength capable of withstanding the molding pressure even after heating. Therefore, molding is easy and reliable, and the obtained denture base has excellent compatibility with the oral impression.

As gypsum, it has an α-type or β-type crystal structure,
Α-type hemihydrate gypsum or β-type hemihydrate gypsum having molecular water of crystallization is used.

The α-type hemihydrate gypsum is obtained by wet-heating gypsum dihydrate, which is the main raw material of gypsum. The β-type hemihydrate gypsum can be obtained by dry heating gypsum dihydrate.

As the calcium carbonate, heavy calcium carbonate produced by crushing limestone or the like, light calcium carbonate produced by baking lime milk with carbon dioxide, or the like can be used.
The calcium carbonate preferably has a particle size of 100 μm or less, particularly 50 μm or less, and a relatively small particle size.

Colloidal silica, which is also called as silcasol, is an ultrafine particle of anhydrous silicon that is used as a colloidal solution in a stable and easy-to-use state. The content of silicon dioxide is 20-
It is generally 50% by weight. Normal particle size is 5 to 90
Since it is an ultrafine particle of about mμ, it easily penetrates into minute voids. Appearance is a transparent milky white or milky white colloidal liquid. If the pH is 11.5 or higher, it easily gels, and
It is stable at 11, but weakly acidic is preferable in terms of handling. If it is neutral or alkaline, it tends to solidify when gypsum and silicon dioxide are mixed, and there is a problem in operability.

The composition ratio of gypsum and calcium carbonate is 30-70 gypsum.
% By weight, 70-30% by weight calcium carbonate, especially gypsum 4
It is preferably 0 to 70% by weight and calcium carbonate 60 to 30% by weight. If the amount of gypsum is less than 30% by weight, the mold becomes hard and brittle, and the mold is damaged by the molding pressure. If the amount of gypsum is more than 70% by weight, the compressive strength of the mold is lowered by the temperature rise and the mold is broken. Also, the mold shrinks violently,
The denture base has poor compatibility with the oral impression.

Colloidal silica is mixed in an amount of 18 to 40 parts by weight with respect to 100 parts by weight of the mixture of gypsum and calcium carbonate. If the amount of the colloidal silica is less than 18 parts by weight, the viscosity of the mixture is too high to be kneaded, and if it exceeds 40 parts by weight, the strength of the denture base molding material becomes insufficient.

The material of the present invention contains, as necessary, an accelerator or a retarder for adjusting the curing time, and a coloring for giving a natural color to the mold, as long as the original strength and thermal properties of the material are not impaired. Agents and the like may be added.

The method for obtaining the material of the present invention is not particularly limited, and a commonly used shaking method or mechanical mixing method can be applied.

The thermoplastic resin used to mold the denture base has (1) no thermal deterioration during molding.

(2) It has an appropriate viscosity and good shapeability.

(3) It can be colored in a color similar to gingiva.

(4) It has appropriate rigidity and moisture resistance, and has good environmental stress crack resistance during use.

Such characteristics are required.

Such resins include polystyrene, polymethylmethacrylate, polymethylpentene-1, polyamide,
Examples thereof include polyester, polycarbonate, ABS resin, polysulfone and the like. In particular, polysulfone resins such as polysulfone and polyether sulfone are preferable because they have excellent moisture resistance, rigidity, environmental stress crack resistance, and the like.

The denture base molding material of the present invention can maintain a high compressive strength of 200 kg / cm ² or more even if it is subjected to heat treatment at 300 ° C. for 1 hour or more. Further, it shows a volume expansion capable of compensating for the volume decrease due to the thermal contraction of the thermoplastic resin. Especially plaster 40
In the composition of ~ 70 wt% and calcium carbonate of 60-30 wt%, the volume expansion of 0.4-0.9% is shown depending on the concentration of colloidal silica, and in a wide temperature range of 150-350 ° C.
It has a stable coefficient of thermal expansion of 07-0.15%. Therefore, excellent molding dimensional properties that are not affected by the heating and softening conditions of the thermoplastic resin can be obtained. Further, the denture base molding material of the present invention does not cause cracks even by rapid heating, and a denture base molding die having excellent shape stability and strength can be obtained. Furthermore, the specific gravity of calcium carbonate near room temperature is 2.71,
Since the specific gravity of gypsum is very close to 2.75, a uniform mold can be obtained without causing component separation due to vibration.

The present invention will be described in detail below with reference to Examples and Comparative Examples.

Example 1 60% by weight of alpha hemihydrate gypsum, 40% by weight of ground calcium carbonate
After mechanically and thoroughly mixing with 100 parts by weight of this mixture, 20 parts by weight of a colloidal silica solution having a powder-liquid ratio of 0.22 was kneaded to embed the wax denture. A split mold for forming a denture was created. After the upper and lower molds were dried, the polysulfone was softened on the lower mold and the upper mold was crimped to form a denture base. The polysulfone denture base taken out after cooling was faithful to the impression of the oral cavity and no mold crack was observed.

Example 2 A denture base was molded in the same manner as in Example 1 except that the powder was mixed with a colloidal silica liquid having a ratio of 0.18.

The obtained polysulfone denture base was faithful to the oral impression, and no mold crack was observed.

Comparative Example 1 A denture base was manufactured in the same manner as in Example 1 except that only α hemihydrate gypsum was used. The resulting polysulfone denture base showed cracks in the mold and was poorly compatible with the oral impression.

Comparative Example 2 A mold was prepared in the same manner as in Example 1 except that 40% by weight of α-hemihydrate gypsum and 60% by weight of cristobalite were used. When a polycarbonate denture base was manufactured at a lower mold temperature of 220 to 250 ° C., a good product was obtained. However, using the same mold, the lower mold temperature was 320 ° C.
When a polysulfone denture base was manufactured as follows,
A denture base with a mucosal surface larger than the oral impression was obtained, and the necessity of composition preparation under lower mold heating temperature conditions was recognized.

Claims (1)

[Claims] 1. A thermoplastic resin denture base molding in which 18 to 40 parts by weight of colloidal silica is mixed with 100 parts by weight of a mixture of 30 to 70% by weight of gypsum and 70 to 30% by weight of calcium carbonate. Mold material.