Effect of Aging Procedures on Phase Transformation of Posterior 3-Unit Zirconia Frameworks Used in Fixed Partial Dentures

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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.