Effect of immediate pre-endodontic dentin sealing on the fracture strength of endodontically treated teeth: An in vitro study

Objectives: Sodium hypochlorite irrigation adversely affects resin–dentin bonding and may compromise restoration longevity. Immediate pre-endodontic dentin sealing (IPDS) has been proposed to preserve dentin bond integrity before irrigation procedures. However, its influence on fracture strength of endodontically treated teeth remains unclear. This study aimed to evaluate and compare the effects of IPDS and late dentin hybridization (LDh) combined with different irrigation activation systems on fracture resistance of endodontically treated teeth. Methods: Thirty-five extracted human mandibular premolars were included and allocated into experimental groups based on dentin sealing protocol (IPDS or LDh) and irrigation activation technique (sonic, ultrasonic, or side-vented needle), along with a control group of sound teeth. Standardized MOD cavity preparation and root canal treatment were performed, followed by adhesive restoration. All specimens underwent thermocycling to simulate oral conditions. Fracture strength testing was carried out using a universal testing machine, and fracture loads were recorded in Newtons. Results: Teeth with immediate pre endodontic bonding sealing combined with ultrasonic irrigation had a greater fracture resistance than the other groups. Conclusions: The findings of this study are expected to provide insights into the role of pre-endodontic dentin sealing and irrigation activation techniques on the structural reinforcement of endodontically treated teeth. This may help clinicians optimize restorative protocols to improve long-term clinical outcomes.