Introduction: Fracture resistance of teeth is affected by cavity preparation design and type of restorative material. Combination of ceramic and polymer phases resulted in materials with better properties and can be used for fabrication of indirect restorations with the CAD/CAM technology.
Objective: To evaluate fracture resistance and mode of fracture of maxillary premolar teeth restored with inlays and onlays fabricated from different CAD/CAM materials.
Methods: Forty-five sound human maxillary premolars were used. Nine specimens were left intact as control group (Group I). The rest were divided into two groups (n=18); MOD inlay (Group II) and MOD complete onlay (Group III). Each group was subdivided into two subgroups (n=9) according to the materials used; VITA Enamic (VE) and Lava Ultimate (LU). Cementation was done by self-adhesive resin cement RelyX™ U200. Specimens were subjected to thermocycling and fracture resistance test was done using a universal testing machine. Mode of fracture was detected by stereomicroscope. Data was analyzed using Two Way ANOVA and Tukey's test. Fracture mode was compared using Monte Carlo simulation of Pearson Chi Square test.
Results: Statistical significant difference was found between control group and Group IIIa (VE onlays) and Group IIIb (LU onlays), with no significant difference among other groups. Pattern I mode of fracture was shown mostly in the onlays while VE inlays demonstrated Pattern III and most LU inlays showed Pattern IV.
Conclusions: Inlays showed the highest fracture resistance. Vita Enamic and Lava Ultimate showed comparable results regarding fracture resistance, regardless of the preparation design.