Evaluation of the effect of toothpastes with different contentson the optical properties of monolithic zirconia

Monolithic zirconia is preferred to prepare restorations with improved aesthetic and mechanical properties. However, toothpaste and gastric acid can have an effect on the optical properties of monolithic zirconia of different material thicknesses. In addition, these possible effects of gastric acid on monolithic zirconia material and the degree of effectiveness of anti-erosion toothpastes are not clear in the literature. Therefore, the aim of this thesis study is to evaluate the effects of toothpastes with different contents and gastric acid on the optical properties of monolithic zirconia material in various thicknesses by means of CIELAB (∆E) and CIEDE2000 (ΔE00) parameters. A total of 63 specimens in two different thicknesses (0.8 mm and 1.0 mm) were prepared from monolithic zirconia (in Coris TZI C, Sirona Dental; Germany). After the sintering process was completed, the L*, a*, b*, C (chroma) and h (hue) values of the samples were measured on a gray background by means of a spectrophotometer (Easy Shade Advance 4.0 Vita Zahnfabric; Germany). Afterwards, the samples were brushed with toothpaste in the simulated brushing unit and the color measurements were repeated on the gray background, and ∆E1 and ∆E001 values were calculated. After this process, simulated gastric acid was applied to the samples, and ∆E2 and ∆E002 values were calculated by completing the final color measurements of the samples on a gray background. Scanning electron microscope (SEM) images were used to analyze the effect of brushing and acid application on the material surface. Mann Whitney U and Kruskal Wallis tests were used in the statistical evaluation of the data. The data obtained from repeated measurements were statistically evaluated with the Friedman Halton and Wilcoxon Signed Rank tests. When the effects of toothpaste and gastric acid application on the color change were evaluated, no color change was observed in the 0.8 mm thick group from the samples brushed with different toothpastes. on the other hand, the ΔE1 and ΔE001 values of the 1.0 mm thick samples in the Promine toothpaste group were found to be significantly higher than Tam Koruma toothpaste group(p=0.001), (p=0.001).When the color changes after gastric acid application were evaluated, the ΔE002 values after acid application were significantly higher in the Promine toothpaste group, which is one of the 0.8 mm thick samples (p= 0.001). However, color changes were not clinically noticeable. According to the findings of the study, it was determined that the effect of brushing with different toothpastes and gastric acid application on the color change of monolithic zirconia material was below the clinical detectability level and the changes in all groups were below the clinically observable threshold.