Effects of sintering protocols on dental zirconia with microstructural gradation: Adhesion to resin cement

• Grant number: 25/19340-3
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: December 01, 2025
• End date: November 30, 2026
• Field of knowledge: Health Sciences - Dentistry - Dental Materials
• Principal Investigator: Camila da Silva Rodrigues
• Grantee: Gabriely Zamarchi Zanella
• Host Institution: Instituto de Ciência e Tecnologia (ICT). Universidade Estadual Paulista (UNESP). Campus de São José dos Campos. São José dos Campos , SP, Brazil

Abstract

Dental zirconias with a microstructural gradient have been developed to combine high mechanical strength and varying levels of translucency within a single piece. Rapid sintering protocols are performed to optimize the firing time of zirconia restorations, but they may influence the grain size of the material. In this context, it is possible that the adhesive behavior at the transition layer between microstructures differs from that at the extremities, since the sizes of cubic and tetragonal grains are distinct. Moreover, the potential effect of temperature on grain size, including the transition layer, may result in different outcomes regarding adhesive behavior. Therefore, the present study aims to evaluate the effect of sintering protocols (conventional and speed) on the bond strength of different layers of microstructure-graded zirconia to a resin cement. For this purpose, discs of zirconia-based ceramic with a microstructural gradient (Katana YML) will be fabricated and divided according to the sintering protocol: rapid (total time: 54 min) or conventional (total time: 7 h). All specimens will receive sandblasting with aluminum oxide particles (50 µm). Each layer of the ceramic (cervical, transition, and incisal) will receive two cylindrical tubes that will serve as matrices to be filled with dual-cure resin cement. Half of the specimens will be tested for micro-shear bond strength 24 hours after cementation, and the other half after thermocycling aging in a thermal cycler for 10,000 cycles. Additional analyses of failure mode, contact angle, and grain size will also be conducted.