Fracture resistance of endodontically treated premolars restored with CAD-CAM onlays

Abstract

PURPOSE: To evaluate the fracture resistance of endodontically treated premolars restored with CAD-CAM onlay restorations. METHODS: 60 extracted mandibular first premolars were selected and at first divided into three groups regarding treatment options: MOD onlay with buccal cusp coverage, MOD onlay with buccal cusp coverage + endodontic treatment, MOD onlay with buccal cusp coverage + endodontic treatment + fiber post. Then, all groups were divided into subgroups (n=10) according to the restorative material used: IPS e.max CAD and Lava Ultimate. Each group was submitted to 5,000 thermal cycles, embedded in acrylic resin and secured in a universal testing machine respectively. A compressive load was applied until fracture, at a crosshead speed of 0.5 mm/minute. Statistical significance among each group was analyzed using one-way ANOVA and Bonferroni tests. RESULTS: Statistically, endodontically treated IPS e.max onlays had numerically the lowest average fracture resistance [753.1 (± 224.9) N/mm² ] among all treatment options. IPS e.max onlays treated with fiber posts had significantly higher resistance than that of endodontically treated IPS e.max CAD group (P= 0.013). Endodontically treated teeth restored with Lava Ultimate onlays [1,381.0 (± 471.7) N/mm²] showed significantly higher averages of fracture resistance than IPS e.max CAD onlays. CLINICAL SIGNIFICANCE: CAD-CAM composite (resin nanoceramic) onlays resist greater forces compared to ceramic restorations. Fiber posts could improve the fracture resistance of endodontically treated mandibular premolars following the ceramic CAD-CAM onlays.