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Abstract

We hypothesize that the fracture resistance of alumina core/porcelain veneer disks increases and that crack initiation shifts from veneer to core as the core/veneer thickness ratio (t_c/t_v) increases from 0.5/1.0 to 1.3/0.2, or as the elastic modulus of the supporting substrate (E_s) to which it is resin-bonded increases from 5.1 to 226 GPa. When supported by a low-modulus substrate, disks with low tc/tv ratios exhibited cracks in the veneer and within the core, while those with high t_c/t_v ratios demonstrated core cracks, but not veneer cracks. None of the disks supported by Ni-Cr alloy (E = 226 GPa) exhibited core cracks. These results support the hypothesis that the crack initiation site shifts as the t_c/t_v ratio increases, but the increase in Es did not affect the crack initiation site. This study suggests that the t_c/t_v ratio is the dominant factor that controls the failure initiation site in bilayered ceramic disks.

Keywords

alumina core elastic modulus failure mode failure load finite element stress analysis.

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Crack Initiation Modes in Bilayered Alumina/Porcelain Disks as a Function of Core/Veneer Thickness Ratio and Supporting Substrate Stiffness

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