An In Vitro Study to Evaluate the Effect of Artificial Aging on Translucency, Contrast Ratio, and Color of Zirconia Dental Ceramic at Different Sintering Levels

Increasing demands for aesthetically pleasing dental restorations have promoted the use of materials that display superior optical properties. Zirconia-based all-ceramic systems have good optical properties, thus providing the desired esthetics for dental restorations. The altered oral conditions impact the physical properties of these materials. Multiple studies have been conducted to evaluate the effect of aging on the mechanical properties of computerized-aided design and computerized-aided manufacturing (CAD/CAM)-based zirconia; however, there is a scarcity of literature discussing the effect of aging on change in translucency, contrast ratio, and color. Therefore, this research aimed to evaluate the effect of accelerated artificial aging on translucency parameter (TP), contrast ratio (CR), and color of CAD/CAM zirconia at different sintering temperatures. Twenty-eight rectangular-shaped specimens were obtained by CAD/CAM milling of zirconia blank. Sintering of the samples was carried out at four different temperatures 1350 degrees C, 1400 degrees C, 1450 degrees C, and 1500 degrees C, respectively. Thermocycling of the samples was performed in a thermocycler. TP, CR, and color evaluation of all the samples was done again using a Spectrophotometer. Data acquired were statistically evaluated by one-way ANOVA and Post Hoc test. The highest amount of change in TP was recorded for specimens sintered at 1400 degrees C (1.86), whereas the least change was attributed to 1350 degrees C (0.51). The highest change in CR was observed in specimens sintered at 1500 degrees C (0.0971), and the least change in CR was observed at 1450 degrees C (0.0086). The highest Delta E values were recorded for 1400 degrees C against both white (1.86) and black background (2.17), whereas the least change was attributed to 1350 degrees C against white (0.86) and against a black background (1.41). The changes in TP were significant, but CR did not show any significant change. Delta E values for all the experimental groups were significant, but were below the clinically perceptible range. An increase in sintering temperature increased the translucency.

Automated summary

This study evaluated the changes in translucency, contrast ratio, and color of CAD/CAM zirconia after accelerated artificial aging at different sintering temperatures. The results showed that an increase in sintering temperature led to an increase in translucency, while contrast ratio and color change were not significant.