Abstract
BACKGROUND: The effect of immediate dentin sealing (IDS) or delayed dentin sealing (DDS) on bond strength of different ceramic occlusal veneer restorations, was not examined yet, but the digital quantification of surface area of preparations helped in the calculation of the actual bond strength of these restorations, besides that, dentin sealing could influence the fracture resistance values of different ceramic occlusal veneer restorations. This study aimed to examine the effect of different dentin sealing strategies and different restorative materials on the debonding forces, bond strength and fracture resistance of occlusal veneer restorations. MATERIALS AND METHODS: Human mandibular molars (N = 64/test) were prepared for occlusal veneer restorations fabricated from Lithium disilicate ceramic (LS) (control group), Zirconia-reinforced lithium Silicate ceramic (ZLS), High translucent zirconia ceramic (HZ), and Resin nano ceramic (LU) (n = 16). Each material was subdivided according to IDS or DDS application, (n = 8). Bond strength testing and fracture resistance values were measured using universal testing machine. Two-way ANOVA was performed to investigate the effects of the two variables, dentin sealing and material selection, and their interaction (α = 0.05), followed by One-way ANOVA and post hoc or Student t-test for further determination of significance. RESULTS: For debonding forces and bond strength testing there were significant differences regarding different materials and dentin sealing strategies, while for fracture resistance, the material selection had a significant effect on it with no significant effects of dentin sealing strategies. The interaction between materials and dentin sealing showed no significant differences concerning all tests. For debonding forces and bond strength there was a higher result related to IDS application than DDS (p < 0.001*), and there was a significant effect of material selection on them (LS > ZLS > HZ > LU), (p = 0.001(*)). Regarding the fracture resistance there was significant increase of all studied materials than LU (p = 0.002(*)). CONCLUSION: Immediate dentin sealing increased the required debonding forces of occlusal veneers made of different materials and their bond strength without significant effect on their fracture resistance, however this improvement was found to be material dependant. All the used materials can withstand lateral and occlusal forces higher than the values recommended for restoring posterior teeth.