Effect of Thickness and CAD/CAM Materials on the Fracture Resistance of Biomimetic Occlusal Veneers

Background: Glass ceramics occlusal veneers are one of the currently used conservative options for repairing excessive Occlusal surface tooth loss by using adhesive techniques, allowing limited reduction of the tooth structure.Methods: Extracted premolar teeth (n=28) were collected, randomized according to materials into two groups (n=14): E-Max CAD and Celtra Duo then randomized into subgroups (n=7) according to occlusal veneer thicknesses 1 mm and 1.5 mm. Teeth were reduced then sealed by dentine bonding agent. Construction of the occlusal veneers was done by CAD/CAM milling machine. Occlusal veneers were cemented by dual cure resin cement. All veneers were exposed to thermocycling and cyclic loading then loaded till failure by universal testing machine,failure mode was assessed using digital microscope. The impact of ceramic type, thickness, and their interactions on fracture resistance was investigated using a two-way ANOVA test. Failure mode data were obtained. The significance level was set at P ≤ 0.05.Results: Two-way ANOVA showed that ceramic type (P-value = 0.221) and thickness (P-value = 0.704) had no statistically significant influence on fracture resistance with mean values of 1573.3 N and 1542.9 N for E-Max CAD 1mm and 1.5 mm thickness respectively. For Celtra Duo mean fracture resistance values were 1518.4 N and 1343.7 N respectively. The majority of the samples exhibited Fracture in restorations only.Conclusions: Both glass ceramic materials performed equally well at 1 mm and 1.5 mm thicknesses. Favourable failure with fracture of restoration only and no damage to the tooth structure with glass ceramic occlusal veneers.