Purpose: To evaluate the influence of restoration bonding and preparation type on the load bearing capacity of a tooth restored with an indirect glass-ceramic or hybrid-ceramic occlusal veneer restoration.

Materials and methods: Occlusal surfaces of extracted human molar teeth were prepared for indirect occlusal veneers with or without circumferential chamfer. The occlusal veneers were milled either from CAD/CAM hybrid- ceramic (HC; Cerasmart, GC Dental), or lithium-disilicate glass-ceramic (LDGC; IPS e.max CAD, Ivoclar) blocks. Finalized veneers were bonded to teeth following manufacturers' instructions or according to the technique for the intended deteriorated bonding using n-hexane wax solution preconditioning on restorations (n = 8/group). The ultimate fracture load was recorded, and fracture types were analyzed and classified visually. Statistical analysis was performed using one-way ANOVA.

Results: The highest fracture load was recorded in teeth with bonded LDGC veneer (P ≤ .0007). The bonded HC veneers had only a marginally higher fracture load compared to nonbonded veneers. In all groups with deteriorated bonding, veneers loosened without tooth fracture, whereas in the bonded veneer groups tooth fractures were observed, especially in teeth restored with LDGC material.

Conclusions: Bonded LDGC occlusal veneers have high load-bearing capacity that exceeds the fracture resistance of tooth structure. Circumferential chamfer preparation for an occlusal veneer has no influence on fracture load of a restored tooth.