Assessment of fracture resistance of occlusal veneers with buccal or lingual extensions compared to conventional occlusal veneers restoring worn molars after thermo-mechanical aging

Abstract
Aim of Study: The aim of this study was to evaluate the fracture resistance of occlusal veneers with buccal or lingual extension compared to conventional occlusal veneers when restoring worn molars relying on the concept of increasing enamel surface area to gain more bond strength.
Methodology: Twenty-Four extracted sound molars were collected and randomly divided into three groups as follows according to the design of the preparation. Group I Conventional Occlusal veneer design, Group II Occlusal veneer with buccal extension, and Group III Occlusal veneer with lingual extension. Immediate dentin sealing protocol was applied for all samples. All the restorations were fabricated from Lithium Disilicate. The sealed dentin was sandblasted and total selective etching was applied. A dual cured resin cement (Multilink speed, IvoclarVivadent) was used to cement the occlusal veneers. After storage for 7 days the samples were subjected to 10,000 Thermocycles followed by 150,000 cycles at the chewing simulator. Fracture resistance was tested using Universal testing machine
Results:Kruskal-Wallis test was used for statistical analysis. There was no significant difference between all groups. The mode of fracture of occlusal veneers with buccal extension showed 42.8% vertical fractures in restoration and tooth structure. Different extension showed no significant statistical difference in fracture resistance values.
Conclusion: There was no significant difference between conventional occlusal veneers design compared to buccal and lingual extension groups. Occlusal veneer restorations of worn molars should be defect oriented, there is no need for unnecessary sound tooth involvement to enhance bonding.