The effect of core:dentin thickness ratio on the bi-axial flexure strength and fracture mode and origin of bilayered dental ceramic composites.

ABSTRACT

OBJECTIVES: The aim of the current study was to assess the effect of coredentin thickness ratio on the flexure strength, fracture mode and origin of bilayered dental ceramic composite disc specimens. METHODS: Sets of 30 bilayered composite discs with coredentin thickness ratio of 21, 11 and 12 were tested in bi-axial flexure with both the reinforcing core and veneering dentin loaded in tension. Mean flexure strengths, standard deviations and associated Weibull Moduli (m) were determined. A combination of optical and scanning electron microscopy was employed for identification of the fracture mode and origin. RESULTS: The coredentin ratio influenced the bi-axial flexure strength and reliability of the flexure strength data when both the reinforcing core and veneering dentin porcelain were tested in tension. The strength and reliability was increased for a coredentin thickness of 21. The number of fracture fragments, the frequency of occurrence of specimen delaminations, Hertzian cone formations and sub-critical radial cracking in the bilayered dental ceramic composite disc shaped specimens was also dependent on the core/dentin ratio and the surface loaded in tension. CONCLUSIONS: Coredentin thickness ratio influences the bi-axial flexure strength and fracture mode and origin in bilayered dental ceramic composite specimens.