The Effect of Hydrothermal Aging on Flexural Strength and Translucency in Niobium-Containing Fully Sintered and High-Speed Sintered Protocols Applied Partially Sintered Monolithic Zirconia Materials

AbstractObjective: The effects of hydrothermal aging on the flexural strength and translucency of niobium-containing fully sintered and high-speed sintering protocol applied semi-sintered monolithic zirconia materials were investigated.Materials and Methods: Three different monolithic zirconia materials, Perfit-FS, Katana STML and Katana UTML, were used. A total of 72 disc-shaped specimens (12x1.2 mm) were produced. KATANA STML and UTML specimens were subjected to high-speed sintering protocol (1560°C, 90 minutes). The aging process was performed in an autoclave at 134 °C under 2 bar for 5 hours, in accordance with ISO 13356 standards. Translucency was evaluated with a spectrophotometer, surface topography analyzed by FESEM, and biaxial flexural strength assessed through the piston on three ball test. Statistical analyses were performed using ANOVA, Bonferroni and Tamhane tests.Results: The translucency values of non-aged Perfit-FS were statistically significantly lower than STML and UTML materials. Flexural strength values of the non-aged materials were similar. The flexural strength of STML significantly increased after hydrothermal aging in comparison with the non-aged group. In contrast, the aged Perfit-FS showed significantly lower translucency and flexural strength relative to the non-aged group. Perfit-FS showed significantly reduced flexural strength relative to STML and UTML in the aged material group.Conclusion: Hydrothermal aging exhibited material-dependent effects on the flexural strength and translucency characteristics of monolithic zirconia materials. STML showed increased strength after aging, while a significant decrease in the mechanical and optical characteristics of Perfit-FS was observed.