Ceren Gizem Karatekin, Gaye Sağlam, Murat Koçak, Sibel Koçak, Baran Can Sağlam
Turkish Endodontic Journal - 2025;10(3):188-194
Effective root canal treatment requires the thorough cleaning of the infected root canal system, removal of necrotic pulp, and obturation of root canal (1). During mechanical root canal preparation, irrigation solutions are used to remove infected dentin chips, eliminate bacteria, and lubricate the canal (2,3). NaOCl is widely used as an irrigation solution in clinical practice due to its ability to dissolve infected tissue. However, hypochlorite solutions can affect the mechanical properties of dentin by degrading organic components. The recommended concentration of NaOCl is between 0.5% and 5.25%, although there is no consensus on the ideal concentration. Although a high concentration of NaOCl can enhance the dissolution of organic tissue, it can also negatively affect dentin (4). Coronal restoration is crucial for the success of endodontically treated teeth. Incomplete or false coronal restoration after successful root canal treatment has been shown to adversely affect tooth survival (5). Therefore, the choice of materials for restoring endodontically treated teeth is of great importance in increasing their resistance to fracture. Composite resin material is widely used in dental practice because of its acceptable aesthetic properties, sufficient adhesion to enamel and dentin, and support of the remaining tooth structure (6). Despite the high compressive strength and fracture resistance of composite resin, polymerisation shrinkage causes marginal gaps and micro-leakage, resulting in hyperemia and hypersensitivity (6). Indirect restorative techniques have been developed to reduce the limitations of direct composite restorations in root canal treated teeth. In recent years, (CAD/CAM) technology has been frequently used in the production of indirect restorations, particularly in the production of aesthetic restorations. The objective of this study was to assess the fracture resistance of teeth that have been treated endodontically and restored by direct and indirect techniques using different concentrations of NaOCl. The first null hypothesis of the study is that irrigation with different concentrations of NaOCl solution does not affect the fracture resistance. The second null hypothesis is that different restoration techniques do not affect the fracture resistance of teeth. 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.
