Determination of the fabricating conditions for the preferable marginal and internal adaptation of the mica crystal castable ceramic crown

Abstract

This study was performed to find an acceptable internal adaptation of castable ceramics containing mica and β-spodumene crystals. The influences of factors, expansion rate of phosphate-bonded investment (A), anisotropic expansion (B), die-coating (C), shrinkage during crystallization (D), and interaction (A X B), and (A X C) were tested by twice repeated experiments under block design according to L8(2)7 orthogonal array. Estimated mean ranges under the conditions combined with significant factors were judged by considering the criteria of the ideal internal gap (about 50 μm). The ideal marginal fit of less than 50 μm and uniform cement space about 50 μm around the axial wall could be achieved by a combination of optimum levels of A1B1C2D2. However, the estimated mean gap at the cusp tip and central fossa of occlusal inside by this combination were about 120 μm. The near intolerable gaps could not be reduced.