The Effect of Hydrothermal Aging on The Color Stability of Gradient Zirconia. In Vitro Study

Abstract

The study aims to assess the influence of hydrothermal aging on gradient zirconia's microstructure and color stability. Materials and methods: Ten discs were constructed from gradient zirconia blanks (3Y-TZP-5Y-TZP) using CAD\CAM technology. Hydrothermal aging was done in an autoclave. Color parameters (a*, b*, L*) for each disc was measured using a spectrophotometer. In order to investigate the zirconia specimens' crystalline structure, X-ray diffraction (XRD) was performed. Color stability and microstructural changes were examined before and after the aging process. Results: Following hydrothermal aging, a statistically significant decrease in the mean (L*) value was found. However, following hydrothermal aging, a statistically significant increase in the mean (a*) and (b*) values was reported. Regarding the microstructure, hydrothermal aging did not result in any significant changes. Conclusion: Artificial aging has led to color changes in gradient zirconia that were in the clinical acceptability range but has no impact on the microstructure of gradient zirconia.