Misfit and fracture load of implant-supported monolithic crowns in zirconia-reinforced lithium silicate

Author(s)

Rafael Soares Gomes

• Document type: Master's Dissertation
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Odontologia de Piracicaba
• Defense date: 2016-02-24

Examining board members

Altair Antoninha Del Bel Cury; Estevam Augusto Bonfante; Lourenço Correr Sobrinho

• Advisor: Altair Antoninha Del Bel Cury

Abstract

Zirconia-reinforced lithium silicate is a ceramic material exclusive for CAD / CAM system recently commercialized, having similar indications to lithium disilicate ceramic, promising superior mechanical properties. The aim of this study was to evaluate the marginal and internal misfit, fracture load before and after thermomechanical cycling in crowns made by zirconia-reinforced lithium silicate (ZLS) and lithium disilicate (LDS). First molars crowns in ZLS and LDS were milled. The crowns had the marginal gap, absolute marginal discrepancy, axial gap and occlusal gap measured by x-ray microtomography (n=8). For fracture load, crowns were cemented in a universal abutment, and divided into 4 groups: ZLS without fatigue, ZLS with fatigue, LDS without fatigue and LDS with fatigue (n=10). The groups with fatigue were subjected to 10,000 thermal cycles (5 °C - 55 °C) and mechanical 1,000,000 cycles (F = 200 N). For fracture load the crowns were subjected to compressive strength test in a universal testing machine at a crosshead speed of 1 mm/min until the occurrence of failure. Through statistical analysis by t test, ZLS showed higher marginal gap values (P=0.000) and absolute marginal discrepancy (P=0.003), while no difference of misfit was found between materials in the axial region and occlusal region. Through two-way ANOVA, mean fracture load of LDS presented higher average fracture load than ZLS both fatigue as without fatigue (P=0.000). The fracture load was not influenced by thermomechanical fatigue. A linear moderate negative correlation was found between the fracture load and marginal misfit (r=-0.553) and between the fracture load and absolute marginal discrepancy (r=-0.497). Considering the limitations of this study, ZLS has lower values to fracture load and higher misfit, although within the limits considered to be acceptable (AU)

• FAPESP's process: 14/23358-0 - Stress distribuition, adaptation and compressive strength of monolithic crowns after thermomechanical loading in different materials
• Grantee: Rafael Soares Gomes
• Support Opportunities: Scholarships in Brazil - Master