Effect of aging procedures on phase transformation of posterior 3‑unit zirconia frameworks used in fixed partial dentures

Abstract

Background: Zirconia is an essential material for dentistry, and its properties should be investigated in all aspects. Aim: The primary objective of this study was to assess the impact of aging procedures on the phase transformation of posterior 3‑unit zirconia frameworks used in fixed partial dentures. Setting and Designs: The study considered three aging procedures: Group T underwent thermocycling with 20,000 cycles between 5°C and 55°C for 30 seconds, Group M experienced mastication cycles with 500,000 cycles at 1.3 Hz and 49 N force, and Group T + M was subjected to consecutive thermocycling (20,000 cycles/5– 55°C/30 s) and mastication cycles (500,000 cycles/1.3 Hz/49 N). Methods: E ach group comprised 12 specimens from manufactured presintered zirconia blocks (inCoris ZI, Sirona, Salzburg, Austria). The evaluation of phase transformation was performed through X‑ray diffraction (XRD) analysis. Statistical Analysis: The obtained data were subjected to statistical analysis using one‑way ANOVA and the Tukey tests (α = 0.05). Results: The study revealed statistically significant differences in the effects of aging processes on phase transformation in zirconia frameworks (P < 0.05). Group T + M demonstrated the highest phase transformation compared to other groups (P < 0.05). Moreover, significant differences were observed between the distal connector and pontic regions (P < 0.05). Conclusion: All aging processes applied to zirconia increased the amount of monoclinic phase.