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Öğe Effect of different surface treatments on the biaxial flexural strength of zirconia ceramics(Mosby-Elsevier, 2023) Ozturk, Caner; Celik, Ersan; Gonuldas, FehmiStatement of problem. Different surface treatments have been applied to zirconia restorations in clinical practice to increase the bond strength between zirconia and cement, but their effect on flexural strength is unknown. Purpose. The purpose of this in vitro study was to evaluate the effect of different surface treatments before and after sintering on the flexural strength of zirconia. Material and methods. Sixty disk-shaped specimens with an initial diameter of 18.6 +/- 0.1 mm and thickness of 2 +/- 0.1 mm were prepared from preshaded presintered 3Y-TZP blocks. The specimens were randomly divided into 3 groups (n=20) according to surface treatments (Group Laser, Group APA, Group Rocatec), and the groups were then divided into 2 subgroups (n=10) according to surface treatment before and after sintering. The phase compositions of the groups were examined by using an X-ray diffractometer (XRD) with 3 randomly selected specimens from each group. Biaxial flexural strength testing was conducted using a universal testing machine to examine the flexural strength of the zirconia specimens. Two-way ANOVA and post hoc least significant difference tests were performed (a=.05). Results. According to the XRD analysis, no monoclinic phases were determined on the surface of the presintered laser-treated specimens, but tetragonal phases were observed on the surface of the postsintered specimens. Surface treatment type and application stage (presintering to postsintering) have a significant effect on the biaxial flexural strength of the specimens (P<.05). The lowest biaxial flexural values were observed in the Laser group, and postsintered specimens showed higher biaxial flexural strength than presintered specimens (P<.05). Conclusions. Postsintered specimens showed higher monoclinic content than presintered specimens. Laser-treated specimens showed the lowest biaxial flexural strength for both presintered and postsintered specimens. (J Prosthet Dent 2023;129:220.e1-e5)Öğe Influence of bleaching agents on the color change and translucency of resin matrix ceramics(Wiley, 2020) Ozturk, Caner; Celik, Ersan; Ozden, Asiye NehirObjective The aim of this study was to investigate the color change, translucency, and whiteness index of three different resin matrix ceramics and a resin composite subjected to different bleaching agents. Materials and Methods Twenty disc-shaped specimens (A2 shaded) for three different resin matrix ceramic brands (Groups Ena, Ulti, and Cera) (totally 60) were prepared using the CAD/CAM technique and 20 nanofiller composite specimens (Group Comp) (A2 shaded) with the same dimensions were prepared as the control group. The color change ( increment E-00), relative translucency parameter (RTP), and whiteness index (WID) of the specimens initial and after different bleaching procedures (home-bleaching and office-bleaching) were calculated using increment E-00, TP00, and WI(D)formulas. Two-way analysis of variance (ANOVA) and multiple comparison test with Bonferroni correction (alpha= .05) at the significance level ofP < .05 were performed for the comparisons of increment E(00)values. The RTP and WI(D)values were evaluated by using repeated measures ANOVA and multiple-comparison test with Bonferroni corrections (alpha= .05) at the significance level ofP < .05. Results Bleaching procedure and material type were found to be significant regardless of bleaching type for RTP and WI(D)values. Material type has a significant effect on the increment E(00)values. The highest color change values were determined in Group Comp (P < .05). Conclusions Bleaching procedures significantly affected the RTP values of Groups Ulti and Cera (P < .05). increment E(00)values for the resin matrix ceramics after the bleaching procedures were below the clinically acceptable values, regardless of the bleaching agent. Clinical Significance Optically, materials such as resin matrix ceramics have properties different from not only enamel and dentin but also among themselves. The possible effect of bleaching agents on these materials should be considered carefully while choosing the restorative material.Öğe Influence of heating rate on the flexural strength of monolithic zirconia(Korean Acad Prosthodontics, 2019) Ozturk, Caner; Celik, ErsanPURPOSE. Fabrication of zirconia restorations with ideal mechanical properties in a short period is a great challenge for clinicians. The purpose of the study was to investigate the effect of heating rate on the mechanical and microstructural properties of monolithic zirconia. MATERIALS AND METHODS. Forty monolithic zirconia specimens were prepared from presintered monolithic zirconia blanks. All specimens were then assigned to 4 groups according to heating rate as Control, Group 15 degrees C, Group 20 degrees C, and Group 40 degrees C. All groups were sintered according to heating rates with the sintering temperature of 1500 degrees C, a holding time of 90 minutes and natural cooling. The phase composition was examined by XRD analysis, three-point bending test was conducted to examine the flexural strength, and Weibull analysis was conducted to determine weibull modulus and characteristic strength. Average grain sizes were determined by SEM analysis. One-way ANOVA test was performed at a significance level of 0.05. RESULTS. Only tetragonal phase characteristic peaks were determined on the surface of analyzed specimens. Differences among the average grain sizes of the groups were not statistically significant. The results of the three-point bending test revealed no significant differences among the flexural strength of the groups (P>.05). Weibull modulus of groups was ranging from 3.50 to 4.74. The highest and the lowest characteristic strength values were obtained in Group 20 degrees C and Control Group, respectively. CONCLUSION. Heating rate has no significant effect on the flexural strength of monolithic zirconia. Monolithic zirconia restorations can be produced in shorter sintering periods without affecting the flexural strength by modifying the heating rate.
