Effect of Surface Roughness on Flexural Strength of Veneer Ceramics

Effect of Surface Roughness on Flexural Strength of Veneer Ceramics
2003
H. Fischer1,2,*, M. Schâfer1, and R. Marx1
Journal of Dental Research

© 2003 International and American Associations for Dental Research

1 Department of Dental Prosthetics, Section of Dental Materials, University RWTH Aachen, Germany; and
2 Department of Ceramics and Refractory Materials, University RWTH Aachen, Mauerstrasse 5, D-52064 Aachen, Germany;

*corresponding author, h.fischer@rwth-aachen.de

ABSTRACT

The strength of ceramic restorations depends on the occlusal surface roughness of the veneering porcelain, which is influenced by the final preparation. The hypothesis of the study was that roughnesses below a critical microscopic defect sizeÛbased only on fracture mechanics considerationsÛalso affect flexural strength. The bending failure stress was evaluated on standard specimens of 4 veneer ceramics with 4 different surfaces of defined roughnesses, respectively. A linear correlation was found between roughness and failure stress. A "roughness-free" failure stress value was predicted for each tested material. This theoretical value can represent the "true" strength of the respective ceramic material. We conclude from our results that the final preparation of a ceramic restoration is critical to the strength of the material, and that ceramic veneering materials can be compared more objectively with respect to their strength by means of roughness-free strength values.

KEY WORDS: dental ceramics Ô surface roughness Ô failure stress Ô roughness-free strength

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