Influence of metal thickness on stress distribution in metal-ceramic crowns.

The objective of this study was to calculate the stress distribution induced in anterior metal-ceramic crowns fabricated with either gold-alloy or nickel-alloy copings of reduced thickness using plane stress analyses. Two-dimensional finite element models of three crown designs were subjected to a simulated biting force of 200 N which was distributed over porcelain near the lingual metal-ceramic junction. Based on plane stress analyses, the maximum tensile and compressive stresses in porcelain for the three cases were 29.5 MPa and 123.1 MPa, respectively. The highest tensile strains in porcelain for veneered Ni-Cr and Au-Pd copings with conventional dimensions were 0.016% and 0.014%, respectively. The maximum stresses and strains in porcelain for the crowns with a conventional coping thickness (0.3 mm) and a reduced coping thickness (0.1 mm) were not significantly different. All values were below the critical failure values of porcelain.