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Updated: Jul 23, 2026

Additive Manufacturing of Functionally Graded Ceramic Materials by Stereolithography
Published on: January 25, 2019
Crack initiation modes in bilayered alumina/porcelain disks as a function of core/veneer thickness ratio and
1First Department of Prosthodontics, Faculty of Dentistry, Tokyo Medical and Dental University, Japan. n.waka.pro1@dent.tmd.ac.jp
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 t(C)/t(V) 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 E(S) 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.
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