FINITE-ELEMENT ANALYSIS OF STRESS-DISTRIBUTION IN PORCELAIN DISCS

Achievement of a controlled stress distribution in feldspathic porcela in is essential for successful dental restorations. In this study, a p rogram for visco-elastic finite element analysis (FEM) of the stress d istribution produced during processing of porcelain was developed. Thi s method was applied to simulate the stress change in porcelain discs that were subjected to convective cooling. The heat transfer coefficie nt was assumed to be 2.1 mu J mm(-2) min(-1) degrees C-1 at the surfac e of the discs. These discs were 2 mm in thickness and had radii varyi ng between 4.8 and 38 mm. As the discs cooled from their sintering tem perature, stresses initially developed at about 600 degrees C. Residua l tensile stress of 8.3 MPa was produced at the centre of the top surf ace of a 16-mm diameter disc compared with a compressive stress of -7. 6 MPa for a 50-mm diameter disc.