Translucency of monolithic and core zirconia after hydrothermal aging

Abstract

Objective: To evaluate the hydrothermal aging effect on the translucency of partially stabilized tetragonal zirconia with yttria (Y-TZP) used as monolithic or fully milled zirconia and of core type.

Methods: Twenty disc-shaped specimens (1 and 10 mm) for each type of monolithic and core Y-TZP materials were milled and sintered according to the manufacturer’s instruction. The final specimens were divided into two groups according to the type of Y-TZP used. Translucency parameter (TP) was measured over white and black backgrounds with the diffuse reflectance method; X-ray diffraction (XRD) and scanning electron microscope (SEM) were used to analyze the microstructure of both Y-TZP types before and after aging. Data for TP values was statistically analyzed using Student’s t-test.

Results: Monolithic Y-TZP showed the highest TP mean value (16.4 ± 0.316) before aging while core Y-TZP showed the lowest TP mean value (7.05 ± 0.261) after aging. There was a significant difference between the two Y-TZP types before and after hydrothermal aging. XRD analysis showed increases in monoclinic content in both Y-TZP surfaces after aging.

Conclusion: Monolithic Y-TZP has a higher chance to low-temperature degradation than core type, which may significantly affect the esthetic appearance and translucency hence durability of translucent Y-TZP.

Keywords:

• Translucent zirconia
• microstructure
• low-temperature degradation

Acknowledgements

My sincere thanks and appreciation to Prof. Michael V Swain, Professor of Biomaterials, Science Research Unit, Faculty of Dentistry, University of Sydney, Australia, for his valuable assistance in the XRD field. My sincere gratitude to Prof. Al-Sayed A Hafez, Professor of Dental Biomaterials, Faculty of Dentistry, Mansoura University, Egypt.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.