Fracture resistance of endodontically treated teeth restored with composite and CAD/CAM resin using different NaOCl concentrations

Purpose: The aim of this study was to evaluate the fracture resistance of endodontically treated teeth restored by direct and indirect techniques using different concentrations of NaOCl.
Methods: Seventy extracted maxillary premolars were used. Ten teeth were not treated (control group). The remaining 60 teeth were divided into two main groups, according to the type of restoration applied: composite and computer-aided design/computer-aided manufacturing (CAD/CAM) (N=30). Standard MOD cavities and access cavities were prepared, according to the groups. Teeth in each main group were divided into three subgroups according to the irrigation used (distilled water, 2.5% sodium hypochlorite (NaOCl) and 5.25% NaOCl) (n=10). During root canal preparation, each subgroup of composite and CAD/CAM was irrigated with distilled water, NaOCl with 2.5% NaOCl concentration and NaOCl with 5.25% NaOCl concentration. After root canal filling, the specimens were restored with nanohybrid composite resin and CAD/CAM technique using nanohybrid composite block. All teeth were subjected to fracture testing using a universal testing machine.
Results: No significant difference was obtained in terms of fracture strength when irrigation solutions were compared in both composite groups and CAD/CAM groups (p>0.05). The fracture strength of the teeth restored with composite resin was statistically significantly higher than the teeth restored with CAD/CAM in each distilled water, 2.5% NaOCl, 5.25% NaOCl solutions (p<0.05).
Conclusion: NaOCl irrigation solution used in root canals did not affect the fracture strength of the teeth. The fracture strength of direct composite restorations used in coronal restorations was higher than that of CAD/CAM restorations.

Keywords: CAD/CAM, composite resin, fracture resistance, NaOCl.