Residual stress measurement in veneering ceramic by hole-drilling.

Objectives: Mismatch in thermal expansion properties between veneering ceramic and metallic or high-strength ceramic cores can induce residual stresses and initiate cracks when combined with functional stresses. Knowledge of the stress distribution within the veneering ceramic is a key factor for understanding and predicting chipping failures, which are well-known problems with Yttria-tetragonal-zirconia-polycrystal based fixed partial dentures. The objectives of this study are to develop a method for measuring the stress profile in veneering ceramics and to compare ceramic-fused-to-metal compounds to veneered Yttria-tetragonal-zirconia-polycrystal ceramic.

Methods: The hole-drilling method, often used for engineering measurements, was adapted for use with veneering ceramic. Because of the high sensitivity needed in comparison with industrial applications, a high sensitivity electrical measurement chain was developed.

Results: All samples exhibited the same type of stress vs. depth profile, starting with compressive at the ceramic surface, decreasing with depth and becoming tensile at 0.5-1.0mm from the surface, and then becoming slightly compressive again. The zirconia samples exhibited a stress depth profile of larger magnitude.

Significance: The hole drilling method was shown be a practical tool for measuring residual stresses in veneering ceramics.