The aim of this study was to evaluate the influence of surface grinding and sandblasting on surface roughness, phase chances, and biaxial flexural strength of yttria-stabilized tetragonal zirconia (Y-TZP) materials. Thirty disk specimens of Cercon (C), DentaCAD (DC), Zirkonzahn (ZZ) were fabricated. The specimens were divided into three groups according to surface treatment (control, ground, and sandblasted). Surface roughness was measured, and X-ray diffraction analysis was performed. Finally, biaxial flexural strength was determined. The data was analyzed by two-way ANOVA. Weibull statistics was used to analyze the variability of strength. The effects of surface treatments on surface roughness values were different for each material. X-ray diffraction analysis revealed that control groups of C and ZZ were composed of tetragonal zirconia. Relative amount of monoclinic zirconia (SD) was 7.366 (0.716)% in the DC control group. In all materials, transformation occurred after treatments. Grinding decreased and sandblasting increased the strength of control groups in all materials. Ground C and DC specimens had higher Weibull modulus than control groups while lower m was found for ground ZZ. Sandblasting, resulted in lower m compared with grinding for all materials although increased strength. The roughness and crystalline phase of Y-TZP materials were influenced by surface treatments. Biaxial flexural strength of materials decreased after grinding and increased after sandblasting. The low m of sandblasted groups may indicate further weakening of the materials, resulting in unexpected failures.

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The purpose of this in vitro study was to evaluate the cytotoxicity of three maxillofacial silicone elastomers at 24, 48, and 72 h on L-929 cells and to determine the effect of accelerated aging on the cytotoxicity of these silicone elastomers. Disc-shaped test samples of maxillofacial silicone elastomers (Cosmesil, Episil, Multisil) were fabricated according to manufacturers' instructions under aseptic conditions. Samples were then divided into three groups: (1) not aged; (2) aged for 150 h with an accelerated weathering tester; and (3) aged for 300 h. Then the samples were placed in Dulbecco's Modified Eagle Medium/Ham's F12 (DMEM/F12) for 24, 48, and 72 h. After the incubation periods, cytotoxicity of the extracts to cultured fibroblasts (L-929) was measured by MTT assay. The degree of cytotoxicity of each sample was determined according to the reference value represented by the cells with a control (culture without sample). Statistical significance was determined by repeated measurement ANOVA (p < 0.01) followed by Duncan's test (p < 0.05). All test materials in each group demonstrated high survival rates in MTT assay (Episil; 93.84%, Multisil; 88.30%, Cosmesil; 87.50%, respectively); however, in all groups, Episil material demonstrated significantly higher cell survival rate after each of the experimental incubation periods (p < 0.05). Accelerated aging for 150 and 300 h had no significant effect on the biocompatibility of maxillofacial silicone elastomers tested (p > 0.05).