The Effect of Thermocycling on the Translucency and Color Stability of Modified Glass Ceramic and Multilayer Zirconia Materials

Aim The aim of this in vitro study was to evaluate the new, multilayered, translucent zirconia and enhanced glass-ceramics to determine if their translucency (TP) and color stability (ΔE) are affected by thermocycling at 10,000, 30,000, and 50,000 cycles. Materials & methods Two pre-shaded, multilayer zirconia products: Prettau(®) 2 Dispersive(® )(PRT) and Prettau(®) 4 Anterior(®) Multi(® )(PRTA), and two glass-ceramic: IPS e.max CAD(®) HT (E.max) and Vita Suprinity(®) HT (VS) were used. All were prepared and sectioned to get plate specimens with dimensions 12.5x14.5x1 mm (n=12) for each material. The L*a*b* values were recorded using a spectrophotometer before and after thermocycling for 10,000, 30,000, and 50000 cycles. The translucencies of the specimens were calculated using the TP formula and the color changes were giving by the color differences ΔE formula at each interval. Results One-way analysis of variance (ANOVA) was used to analyze the data followed by Scheffe’s post-hoc test and multiple paired t-tests (P < 0.05). There was a statistically significant higher TP for E.max before (16.2) and after aging (16.9) (p<0.001**). All the tested groups showed a statistically significant increase in their TP at different intervals. PRT showed significantly higher ΔE (p<0.001**) after 50,000 cycles. Conclusion There was a mild but significant increase in translucency in both Zirconia and glass-ceramic after thermocycling. In addition, all materials showed a significant color change with time, however, this is not clinically perceptible.