OBJECTIVETo evaluate the effect of core ceramic surface treatment on the failure behaviors of two bilayered all- ceramic structures.

METHODSLithium disilicate glass-ceramic (LDG, IPS e.max Press) and Zirconia(Cercon) specimens were divided into 4 groups(n=12) according to the following surface treatment methods: ground successively to 1 000(group A), 600(group B) and 320(group C) grit silicon carbide(SiC) papers and sandblasted with 110 µm aluminum oxide particle(group D, as control). Surface roughness was measured using a profilometer. After veneer sintering, the flexural strength σ was measured with biaxial flexure test and the reliability of strength was analyzed with Weibull distribution. Failure modes and fractographic patterns were analyzed by optical stereo and scanning electron microscopy (SEM).

RESULTSFor LDG, no significant difference was found for the flexural strength values among groups (F=0.406, P=0.750). No significant difference was found in Weibull modulus among groups(the confidence bounds overlapped with each other). SEM and optical stereo observation results showed that all the bilayered LDG specimens failed cohesively. For zirconia, Mean flexural strength values were (541 ± 75), (533 ± 73), (529 ± 78) and (640 ± 95) MPa for groups A, B, C and D, respectively, and group D demonstrated a significantly higher flexural strength compared to the other three groups(P<0.05). No significant difference were found among groups(the confidence bounds overlapped with each other). Specimens in all groups failed mainly adhesively, while those in group D presented lower percentage of adhesive failure.

CONCLUSIONSCore ceramic surface treatment has no influence on the failure behaviors of LDG based bilayered structures. Sandblasting can increase the flexural strength of bilayered zirconia structures by reducing the incidence of delamination.