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Introduction: Purpose of this study was to evaluate the fracture resistance of occlusal veneer and overlay CAD/CAM restorations made of polymer-infiltrated ceramic and lithium disilicate ceramic.

Methods: 60 non-carious mandibular first molar teeth were divided into 5 groups: Polymer-infiltrated ceramic (PIC)-overlay group (n: 12), PIC-occlusal veneer group (n: 12), Lithium disilicate ceramic (LDC)-overlay group (n: 12), LDC-occlusal veneer group (n: 12) and control group (n: 12) which was consisted of natural teeth. Standard overlay and occlusal veneer cavities were prepared. Restorations were manufactured using CEREC, cemented with adhesive resin cement. All specimens subjected to artificial aging process in mastication simulator, fracture resistance was assessed with universal testing machine. Fractured surfaces were examined with stereomicroscope.

Results: Obtained data were evaluated with 1-way ANOVA, Tukey HSD and Student t tests. In terms of fracture force values, no statistically significant difference was found among groups (PIC Overlay: 2196, 77±427, 84; PIC Occlusal Veneer: 2326, 19±469, 07; LDC Overlay: 1960, 16±438, 85; LDC Occlusal Veneer: 2148, 53±460, 18) except control group (2942, 3±724, 60). In terms of failure modes, no statistically significant difference was found among groups; occlusal veneer restorations showed mostly Burke class I-II fractures.

Discussion and Conclusion: For restorative treatment of posterior worn teeth, minimal invasive occlusal veneer restorations made of LDC or PIC materials are successful alternatives.