Fracture resistance of maxillary molars restored with partial coverage all-ceramic restoration

Objective: This invitro study aimed to assess fracture resistance (FR) of maxillary molars restored with overlay restorations.Materials and methods: Thirty-two maxillary molars were arranged to receive CAD/CAM fabricated occlusal overlays (0.5 mm) and divided into two main groups according to type of ceramic material utilized; either LD (L) or ZLS (Z) ceramic. Each group was further subdivided into 2 equal subgroups, according to surface treatment: either hydrofluoric acid (HF) acid etching and universal primer (Monobond N) (H) or Monobond Etch & Prime (M). Adhesive resin cement (Multilink N) was utilized for bonding. Sixty minutes following bonding, samples were stored in a water (H2O) bath for 90 days, followed by cyclic loading fatigue for 125000 cycles. Fracture of the samples was done by using compressive load in (N) by utilizing a universal testing machine (UTM). The proper statistical analysis was used when needed.Results: Tukey test displayed that there were insignificant differences between all test groups regardless of ceramic types or surface conditioning methods (P>0.05).Conclusions: Neither ceramic materials nor surface treatments affected fracture resistance of minimally thickness overlay restorations.