マイカ系キャスタブル・セラミックス（ＯＣＣ）・クラウンの寸法精度に関する研究

Abstract

This article discussed the dimensional accuracy of Olympus Castable Ceramics (OCC) crowns at the stage of as-cast and crystallization. The master die technique and three coordinate measuring method were used for their measurement. Moreover, the surface roughness of inner crowns were measured and following results were obtained.1. OCC crowns, heat-treated at 850°C were rather expanded than at 900°C or 950°C in the master die technique. But the differences between at 900°C and 950°C were not significant.2. In the master die technique, each crown fabricated with special investment liquid, which was diluted with 25%, 50% and 75% distilled water showed expansional ratios of 0.35%, -0.23%and -0.86%, respectively.3. In the master die technique, buffering factors, ringless, one fold of liner and two folds of liner did not affect the expansional ratio.4. In three-coordinate measuring, each diameter of as-cast crowns expanded equally in the range of 1.0-7.0mm from occlusal plane. But, 9.0mm near the cervical portion expanded less than the others.5. In three-coordinate measuring, about 0.70-0.81% shrinkage were founded at the inner diameter of crystallized crowns.6. In measuring for surface roughness of inner crowns, crystallized crowns were roughened more than as-cast ones in both of Ra and Rmax.