抄録
The new ceramic material (Olympus Castable Ceramics, O. C. C.) was developed for the purpose of fabricating castable crowns.
In order to get the optimum characteristics, its basic composition and the condition of heat treatment for crystalization, the thermal and mechanical properties and the biological tests were investigated.
The following results were obtained:
1. O. C. C. is mainly composed of Li2O, MgO, ZnO, TiO2, Na2SiF6, Al2O3 and SiO2 and also includes ZrO2, Y2O3 and a little amount of metal oxides as the stain.
2. The condition for heat treatment is as follows:
a) As casted O. C. C. is heated to 750°Cin one hour.
b) Maintain at 750°C for two hours.
c) Raise the temperature to 900°C at the rate of 3.3°C/min.
3. Main precipitated crystals are Mica (NaMg3 (Si3AlO10) F2) and β-spodumene (Li20, Al2O
3, 4 SiO2).
4. O. C. C. has high resistance especially to bending strength (2, 800 kg/cm2 at 950°C). The Vickers Hardness Number of O. C. C. is 360-420, which is similar to enamel.
5. Fracture toughness (K1C) of O. C. C. is 2.5-3.0 which is simillar to Al2O3 ceramics.
6. Thermal impact resistance was 36 times larger than that of the human enamel.
7. O. C. C. showed excellent chemical durability and no harmful ions leached out in elution test.
8. No abnormalities were found in any biological test.
From above results, it can be concluded that O. C. C. has many favorable properties as a new type of restorative material for future use.
