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    Effects of 16% carbamide peroxide bleaching on the surface properties of glazed glassy matrix ceramics
    (HINDAWI LTD, 2020) Demir, Necla.; Karci, Muhammet.; Ozcan, Mutlu.
    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.
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    Evaluation of flexural strength of different denture base materials reinforced with different nanoparticles
    (WILEY, 2019) Karci, Muhammet.; Demir, Necla.; Yazman, Sakir.
    Purpose To evaluate the effect of adding Al2O3, 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% Al2O3, 3% Al2O3, 5% Al2O3, 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 (alpha = 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 Al2O3 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%.