Effect of aging and processing on recycled and commercial 3Y-TZP

• Grant number: 24/10843-0
• Support Opportunities: Scholarships in Brazil - Doctorate
• Start date: November 01, 2024
• End date: March 31, 2026
• Field of knowledge: Health Sciences - Dentistry - Dental Materials
• Principal Investigator: Estevam Augusto Bonfante
• Grantee: Mariana Miranda de Toledo Piza
• 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 proposal, associated with the aid Young Researcher phase 2 #2021/06730-7, aims to improve the recycling process through an in-depth study of different sintering temperatures and their consequent impact on the physicochemical properties of recycled material before and after artificial aging in a hydrothermal reactor. The microstructural, optical, and mechanical characterization of a commercially available 3Y-TZP disc for CAD/CAM (control group), a 3Y-TZP (pristine powder) to be pressed in our laboratory, and a recycled 3Y-TZP will be carried out, all of which are composed of the same raw material: second-generation 3Y-TZP. A total of 900 specimens will be produced, which will be divided into 18 experimental groups, where four different sintering temperatures and two conditions will be evaluated: before and after aging. The 3Y-TZP CAD/CAM samples will be milled into cylinders and subsequently cut into discs using a precision cutter (detailed pilot study in this proposal). The specimens of the 3Y-TZP groups, manufactured from commercial powder and recycled powder, will be uniaxially pressed. Sintering will occur at 1450ºC, 1500ºC, 1550ºC, and 1600ºC for 2 hours to understand the different microstructures resulting from the varied sintering times and their relation to the resulting physicochemical properties. Artificial accelerated aging will occur in a hydrothermal reactor for 20 hours at 134ºC and 2.2 bar. The relative density will be calculated using the Archimedes method. X-ray diffraction (XRD) will be used to characterize the crystalline content and scanning electron microscopy (SEM) will be used to observe the microstructure and determine the grain size. The optical properties will be measured by calculating the contrast ratio (CR) and translucency parameter (”5800). The mechanical properties will be evaluated through Vickers hardness and fracture toughness (KIC) calculation, in addition to biaxial flexural strength (BFS) testing, determining characteristic strength (MPa) and Weibull modulus (m).