The effects of repetitive firing processes on the optical, thermal, and phase formation changes of zirconia

PURPOSE: The aim of this study was to investigate the effect of different numbers of heat treatments applied to superstructure porcelain on optical, thermal, and phase formation properties of zirconia. MATERIALS AND METHODS: Forty zirconia specimens were prepared in the form of rectangular prism. Specimens were divided into four groups (n = 10) according to the number of firing at heating values of porcelain. Color differences and translucency parameter were measured, and X-ray diffraction (XRD) analysis and differential scanning calorimetry (DSC) were performed. Data were analyzed with analysis of variance (ANOVA). RESULTS: There were no statistically significant differences in ΔE, TP, L, a, and b value changes of the zirconia specimens as a result of repetitive firing processes (P>.05). CONCLUSION: Although additional firing processes up to 4 increase peak density in thermal analysis, additional firing processes up to 4 times can be applied safely as they do not result in a change in color and phase character of zircon frameworks.