DENTAL INVESTMENT

Abstract

Provided is a dental investment that is a dental phosphate-bonded investment including boron nitride at 0.1% to 5% by weight.

Claims

1. A dental investment that is a dental phosphate-bonded investment including boron nitride at 0.1% to 5% by weight.

Description

EXAMPLES

<Preparation of Dental Investments>

[0020] At compositions indicated in Table 1, dental investments of examples 1 to 5 and comparative examples 1 to 6 were prepared. Note that the unit of each component is % by weight.

<Press Molding Test>

[0021] Next, a press molding test was performed on each prepared dental investment according to the following procedure.

1. 20% by weight of a colloidal silica aqueous solution was mixed with each of the dental investments of examples 1 to 5 and comparative examples 1 to 6 at a proportion in which the colloidal silica aqueous solution was 25 mL with respect to 100 g of the dental investment. Thereby, each dental investment slurry was prepared.
2. An acrylic disk having a diameter of 20 mm was embedded with each dental investment slurry.
3. After each dental investment hardened, each dental investment slurry was placed in an electric furnace at 850 C. for 60 minutes to burn up the acrylic disc to obtain a mold.
4. Using obtained each mold, press molding of a lithium disilicate ingot (e.max HT A2; manufactured by Ivoclar Vivadent Corporation) was conducted under the following conditions.

[0022] Start temperature: 700 C.

[0023] Heating rate: 60 C./min

[0024] Final temperature: 930 C., 15 minutes

[0025] Pressing pressure: 220 N

[0026] Pressing time: 3 minutes

[0027] Heating/press molding machine: GC PANAMAT PRESS (manufactured by GC Corporation)

[0028] Composition of lithium disilicate ingot (e.max HT A2): [0029] SiO.sub.2: 57% to 80% by weight [0030] Li.sub.2O: 11% to 19% by weight [0031] K.sub.2O: 0% to 13% by weight [0032] P.sub.2O.sub.5: 0% to 11% by weight [0033] ZrO.sub.2: 0% to 8% by weight [0034] ZnO: 0% to 8% by weight [0035] Other oxides and ceramic pigment: 0% to 10% by weight
5. Each glass ceramic disc cast by the press molding was recovered from the mold, and sandblasting was performed on the surface of each glass ceramic disc (casting) using glass beads. Thereafter, the surface roughness Ra was measured using a three-dimensional shape measurement device (VR-3100; manufactured by Keyence Corporation), and the surface property of each casting was evaluated with the following index. The evaluation results are indicated in Table 1. [0036] A: Surface roughness Ra is less than 8 m [0037] B: Surface roughness Ra is from 8 m to 15 m [0038] C: Surface roughness Ra exceeds 15 m

[0039] Also, the presence or absence of destruction of each mold during the press molding was evaluated using the following index. The evaluation results are indicated in Table 1. [0040] OK: No problem [0041] NG: Destruction of the mold was found

TABLE-US-00001 TABLE 1 COMPARATIVE (UNIT: % BY WEIGHT) EXAMPLE 1 EXAMPLE 2 EXAMPLE 3 EXAMPLE 4 EXAMPLE 5 EXAMPLE 1 SILICON DIOXIDE 82 69 77 76 65 69 (SILICA) AMMONIUM PHOSPHATE 12 20 14 16 20 20 MAGNESIUM OXIDE 5.5 10 7 7 10 10 BORON (AVERAGE PARTICLE 0.5 1 2 NITRIDE DIAMETER 12 m) (AVERAGE PARTICLE 1 5 DIAMETER 2 m) MOLYBDENUM DISULFIDE 1 GRAPHITE POLY- TETRAFLUOROETHYLENE EVALUATION SURFACE PROPERTY B A A A B C RESULT OF CASTING CRACK OF MOLD OK OK OK OK OK OK COMPARATIVE COMPARATIVE COMPARATIVE COMPARATIVE COMPARATIVE (UNIT: % BY WEIGHT) EXAMPLE 2 EXAMPLE 3 EXAMPLE 4 EXAMPLE 5 EXAMPLE 6 SILICON DIOXIDE 69 69 69 60 40 (SILICA) AMMONIUM PHOSPHATE 20 20 21 20 20 MAGNESIUM OXIDE 10 10 10 10 10 BORON (AVERAGE PARTICLE 10 30 NITRIDE DIAMETER 12 m) (AVERAGE PARTICLE DIAMETER 2 m) MOLYBDENUM DISULFIDE GRAPHITE 1 POLY- 1 TETRAFLUOROETHYLENE EVALUATION SURFACE PROPERTY C C C C C RESULT OF CASTING CRACK OF MOLD OK OK OK NG NG

[0042] As can been seen from Table 1, in a case where press molding of glass ceramics is performed using a dental investment according to the present invention, it is possible to obtain a casting having a favorable surface property.

[0043] In contrast, in a case where an investment does not include boron nitride but includes, as a release agent, molybdenum disulfide (comparative example 1), graphite (comparative example 2), or polytetrafluoroethylene (comparative example 3), a casting having a favorable surface property could not be obtained. Similarly, in a case where an investment includes none of boron nitride and a release agent, a casting having a favorable surface property could not be obtained (comparative example 4). Further, when the content of boron nitride in an investment is excessive, the mold made of the investment was destroyed by high pressure at the time of press molding due to insufficient strength, and a casting having a desired shape could not be obtained (comparative examples 5 and 6).

[0044] The present international application is based upon and claims the benefit of priority of Japanese Patent Application No. 2016-012801, filed on Jan. 26, 2016. The entire contents of Japanese Patent Application No. 2016-012801 are hereby incorporated herein by reference.