Production of experimental 3Y-TZP blocks: Effect of glass-infiltration on the survival of monolithic crowns

• Grant number: 24/16741-4
• Support Opportunities: Scholarships in Brazil - Master
• Start date: April 01, 2025
• End date: March 31, 2026
• Field of knowledge: Health Sciences - Dentistry - Dental Materials
• Principal Investigator: Estevam Augusto Bonfante
• Grantee: Ana Cristina Villanacci Pereira
• 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

The second-generation 3Y-TZP has established itself as a viable option for monolithic applications due to its high mechanical properties. However, aging resulting from low-temperature degradation (DBT) remains a concern. The glass infiltration process has the potential to enhance mechanical performance and provide protection against low-temperature degradation (DBT). Thus, the present project aims to develop an experimental processing method for second-generation 3Y-TZP blocks, from commercial powder, to manufacture monolithic crowns, with subsequent glass infiltration and evaluation through fatigue testing, in comparison with commercial control samples, as proposed in GAP 2 of the Young Researcher Grant 2021/06730-7 to which this proposal is associated. For this porpuse, specimens will be processed through uniaxial pressing into block shapes (n=50) using commercial 3Y-TZP powder, which will be divided into two groups: graded (glass-infiltrated) and ungraded (not glass-infiltrated but glazed), and compared to a control group composed of commercial glazed 3Y-TZP. For all groups, two sample geometries will be obtained: discs and monolithic crowns (molar). After pre-sintering, glass infiltration or glazing, and sintering, the disc specimens will be used to characterize the microstructure and crystalline content through scanning electron microscopy (SEM) and X-ray diffraction (XRD), as well as to evaluate the optical properties using reflectance tests on a spectrophotometer and the mechanical properties through biaxial flexural strength testing, Vickers hardness, and fracture toughness testing. The monolithic crowns (n=15/group) will be adhesively cemented onto milled preparation analogs and subjected to accelerated progressive fatigue testing to analyze survival probability. Qualitative fractographic analysis will be conducted on all fractured specimens. The data obtained from optical evaluations will undergo analysis of variance and Tukey's test. Weibull statistical analysis will be used to assess survival probability, characteristic strength, and Weibull modulus.