Evaluation of mechanical properties of dental ceramic core materials in combination with porcelains.

PURPOSE: This paper describes the mechanical testing of dental ceramic core materials in combination with porcelains to simulate the real service conditions for dental applications.
MATERIALS AND METHODS: The study included Procera AllCeram (densely sintered high-purity alumina); Vita In-Ceram (glass-infiltrated presintered alumina); three dental porcelains (Procera Porcelain AllCeram, Vitadur-N, and Vitadur Alpha); and densely sintered alumina-Procera Porcelain AllCeram two-layer composites, densely sintered alumina-Vitadur-N two-layer composites, and glass-infiltrated presintered alumina-Vitadur Alpha two-layer composites, with different thicknesses of densely sintered alumina or glass-infiltrated presintered alumina, respectively. The flexural tests were performed in ring-on-ring biaxial bending. The flexural failure stresses were determined using both Timoshenko's biaxial loading equation and Shetty's ring-on-ring stress equation. The bending theory of bilayer plates was used to evaluate the failure stresses in the two-layer composites. Weibull statistics were applied to all stress data, and the information was used to estimate the failure probability at selected applied stresses for a comparison of different two-layer densely sintered alumina-porcelain composites.
RESULTS: The failure stress of densely sintered alumina is significantly higher than that of glass-infiltrated presintered alumina as a core dental material under the same testing conditions. The failure stresses of the three commercial dental porcelains are statistically the same.
CONCLUSION: The results show that the densely sintered alumina-Procera Porcelain AllCeram two-layer composite has interesting dental applications.