Hybrid restorative materials occlusal veneers: effect of thickness on misfit, reliability and stress distribtion

Author(s)

Mirelle Maria Ruggiero

• Document type: Master's Dissertation
• Press: Piracicaba, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Odontologia de Piracicaba
• Defense date: 2020-03-02

Examining board members

Altair Antoninha Del Bel Cury; Edmara Tatiely Pedroso Bergamo; Estevam Augusto Bonfante

• Advisor: Altair Antoninha Del Bel Cury

Abstract

Resin-matrix ceramics have been proposed as an alternative to conventional dental ceramics. The combination of the properties of polymers and ceramics provides favorable mechanical properties, such as greater fatigue resistance when compared to conventional ceramics. Such characteristics supports the use of thinner restorations named occlusal veneers, allowing less invasive dental preparation. This study evaluated the misfit, reliability and stress distribution of occlusal veneers (OV) produced in two different resin-matrix ceramics and three thicknesses. One hundred and twenty six OV of a mandibular first molar were milled using a CAD/CAM system and divided according to materials (resin nanoceramic (RNC) or polymer-infiltrated ceramic network (PICN)) and thicknesses (0.5, 1.0 and 1.5 mm), totaling six groups (RNC0.5, RNC1, RNC1.5, PICN0.5, PICN1 and PICN1.5). Marginal gap (MG) and absolute marginal discrepancy (AMD) of sixty (n=10/group) OV were evaluated using a µCT. The mean values were obtained, normal data distribution was confirmed by Shapiro-Wilk test, and data were analyzed using two-way analysis of variance and Tukey Post Hoc test (?=0.5). Step-stress accelerated life testing (n=21/group) was performed with the load applied at the distobuccal cusp tip of the OV until failure or suspension. The use level probability Weibull curves and reliability were calculated and plotted (IC 90%). For the finite element analysis (FEA), axial load of 600 N was applied on the same point of the SSALT test. The stress distribution was evaluated according to the criteria of maximum principal stress (? max ) on the restoration and maximum shear stress (? max ) on the cement layer. There was no significant difference in MG and AMD among all groups. The probability of survival for the estimated mission at 600 N, was significantly lower to PICN1.5 compared to RNC1 and RNC1.5. In addition, reliability significantly reduced from 200 to 400 N and from 400 to 600 N for all groups, except for RNC1 and RNC1.5. The ? max values were higher for PICN than RNC groups and 0.5 mm concentrated more stress than 1.0 and 1.5 mm groups. Both resin-matrix ceramic materials presented promising results when used as occlusal venners given their low marginal gap and high probability of survival (AU)

• FAPESP's process: 18/21317-6 - Material and thickness influence on reliability and internal and marginal adaptation of onlays produced by CAD/CAM technology
• Grantee: Mirelle Maria Ruggiero
• Support Opportunities: Scholarships in Brazil - Master