Recycled 4Y-PSZ Zirconia: Evaluation of Microstructural, Mechanical, and Optical Properties Before and After Hydrothermal Aging

• Grant number: 25/10184-9
• Support Opportunities: Scholarships in Brazil - Doctorate
• Start date: September 01, 2025
• End date: June 30, 2029
• Field of knowledge: Health Sciences - Dentistry - Dental Materials
• Principal Investigator: Estevam Augusto Bonfante
• Grantee: Giovana de Assis Marcolino
• Host Institution: Faculdade de Odontologia de Bauru (FOB). Universidade de São Paulo (USP). Bauru , SP, Brazil
• Associated research grant: 21/06730-7 - Towards sustainable zirconia recycled from milling waste and boosted by glass infiltration for restorative use, and of the development of strong, graded, and aging resistant multilayered zirconia blocks, AP.JP2

Abstract

This doctoral project aims to develop a recycling method for partially stabilized tetragonal zirconia with 4 mol% yttria (4Y-PSZ), derived from waste generated during dental milling processes. Recycled 4Y-PSZ samples will be compared with commercial and experimental samples through microstructural, mechanical, and optical characterization, both before and after hydrothermal aging. The study will involve three main groups: a control group (commercial zirconia sintered at 1450¿°C), an experimental group (sintered at 1450¿°C and 1550¿°C), and a recycled group (sintered at 1450¿°C and 1550¿°C). All protocols-except for the commercial control group-will use a heating rate of 3¿°C/min, with an intermediate dwell at 600¿°C for 1 hour and a final dwell for 2 hours. The commercial group will be sintered according to the manufacturer's instructions at 1450¿°C with a 3¿°C/min heating rate.After sintering, the specimens will be evaluated under immediate conditions and after 10 hours of steam aging, following ISO 6872:2024 standards. Tests will include biaxial flexural strength, microstructural analysis using scanning electron microscopy (SEM), X-ray diffraction (XRD), optical property analysis by spectrophotometry, and fractographic evaluation. For the mechanical strength data, statistical analysis will be performed using Weibull distribution with a 95% confidence interval to determine the Weibull modulus and characteristic strength. For optical properties, one-way ANOVA will be applied, followed by Tukey's post hoc test, with a 5% significance level.The results will assess the impact of recycling on zirconia properties, providing insights into its clinical applicability and contributing to sustainable strategies for reducing dental waste. Finally, pilot feasibility tests with preliminary results will be presented at the end of this proposal. (AU)