Effect of Preparation Design and Ceramic Material on the Fracture Resistance of Onlay Restorations

Abstract

The aim of this in vitro study was to evaluate fracture resistance and failure mode of human maxillary first premolars restored with two ceramic onlay restoration materials prepared with two preparation designs. A total of 40 extracted, human maxillary first premolars were used and divided into two groups according to preparation design A: MOD cavity with anatomical reduction of functional cusp, B: MOD cavity with butt joint reduction of functional. Each group restored with two types of ceramic material: Zirconia-reinforced glass ceramic (Vita Suprinity) and Hybrid ceramic (Vita Enamic). The finished onlay restorations were adhesively luted to prepared teeth using self-adhesive resin cement. Specimens exposed to thermocycling 5000 cycles. Fracture resistance was measured using universal testing machine. Failure mode was evaluated using a stereomicroscopy. Two-way ANOVA was used to study the effect of different tested variables and their interaction. The significance level was set at p≤0.05 within all tests. Two-Way ANOVA showed that Ceramic material had no significant effect on the Fracture resistance of restored teeth. On the other hand, the preparation design had significant effect. The interactions between the independent variables ceramic materials and preparation designs had significant effect on the fracture resistance of teeth.