Effects of 16% Carbamide Peroxide Bleaching on the Surface Properties of Glazed Glassy Matrix Ceramics.

OBJECTIVE: To determine the influence of the home bleaching agent, Opalescence PF, on the surface roughness and microhardness of glazed glassy matrix CAD-CAM ceramics. Materials and Methods. The 28 sintered leucite- and lithium disilicate-reinforced ceramic specimens (IPS Empress CAD and IPS e.max CAD) were divided into control and bleached groups. The home bleaching agent was applied to specimens of bleached groups for 7 days. The surface roughness and microhardness of all specimens were measured. A scanning electron microscope was used to evaluate the surface properties. The data were statistically analyzed by two-way ANOVA. RESULTS: The control e.max CAD showed the lowest surface roughness values. For both Empress and e.max CAD, surface roughness was significantly higher for the bleached group (p < 0.05). No significant differences in microhardness were observed. CONCLUSIONS: According to our study, patients should be careful when using home bleaching agents because whitening agents can affect the mechanical properties of full ceramic restorations like e.max CAD and Empress CAD. Ceramic polishing may be required in clinical situations where ceramic restorations are accidentally exposed to bleaching gels.

Effect of Home Bleaching on the Translucency of CAD/CAM Systems.

PURPOSE: To evaluate the effect of a home bleaching agent (Opalescence PF) on the translucency of CAD/CAM ceramic systems. MATERIALS AND METHODS: The 28 sintered ceramic specimens (IPS Empress CAD and IPS e.max CAD; 15 mm long, 10 mm wide, 1 mm thick) were divided into two subgroups as control and bleaching groups (n = 7). Carbamide peroxide (CP), 16%, home bleaching agent was applied onto the surface of each specimen for 6 hours per day for 7 days. A spectrophotometer (VITA Easyshade Advance) was used to measure the CIE L* a* b* coordinates and the reflectance value (Y) of the specimens on white and black backgrounds. The translucency parameter (TP), contrast ratio (CR), and opalescence parameter (OP) of the specimens were calculated. The data were statistically analyzed using Kolmogorov-Smirnov, one-way ANOVA, Tukey's test, and Pearson's correlation. RESULTS: Statistically significant differences in the TP values after 16% CP bleaching treatment were observed (p ˂ 0.05); however, no significant differences were found in the OP and CR values after the surface treatment (p ˃ 0.05). CONCLUSIONS: According to our study, patients who have all-ceramic restorations in their mouths should be careful when using home bleaching agents, because whitening agents can affect the translucency of all-ceramic restorations such as e.max CAD and Empress CAD.

Evaluation of Flexural Strength of Different Denture Base Materials Reinforced with Different Nanoparticles.

PURPOSE: To evaluate the effect of adding Al2 O3 , SiO2 , and TiO2 nanoparticles in ratios of 1, 3, and 5 wt% to different acrylic resins on flexural strength. MATERIALS AND METHODS: A total of 210 specimens were prepared in 30 groups (n = 7/group) (Control, 1% Al2 O3 , 3% Al2 O3 , 5% Al2 O3 , 1% SiO2 , 3% SiO2 , 5% SiO2 , 1% TiO2 , 3% TiO2 , 5% TiO2 ). The specimens were polished with 200-, 400-, and 600-grit abrasive paper to provide a standard surface before testing and then suspended in distilled water for 30 days. Flexural strength was measured via three-point bending tests. Subsequently, SEM analysis was performed for one specimen from each group. Homogeneity of data was assessed by Kolmogov-Smirnov test followed by two-way ANOVA and Tukey HSD tests (α = 0.05). RESULTS: There was a significant increase in the flexural strength of polymethylmethacrylate (PMMA) after addition of 1% nanoparticles in both heat-polymerized and autopolymerized acrylic resins (p ˂ 0.05). The flexural strength values of the groups to which Al2 O3 and TiO2 nanoparticles were added exceeded those of the group with SiO2 addition (p ˂ 0.05). The electron microscopy images revealed that the nanoparticles were more homogeneously dispersed in PMMA with higher flexural strength. CONCLUSIONS: The mechanical properties of PMMA can be improved by the addition of nanoparticles to PMMA; however, the flexural strength values of PMMA decrease with the addition of nanoparticles at higher percentages (3-5%). Hence, the ideal filler ratio corresponds to 1%.