This randomized controlled clinical trial evaluated and compared coronal strain alterations in posterior teeth before and after single-sitting root canal treatment (RCT) using a custom-made strain gauge under physiologically relevant occlusal loads. Although root canal therapy effectively preserved teeth, endodontically treated teeth were known to be biomechanically compromised due to structural loss and changes in dentin properties. Most previous assessments of strain had been performed in vitro, which did not replicate true functional conditions.

In this in vivo study, 15 patients aged 18–50 years who required single-visit RCT on carious posterior teeth were enrolled. A high-performance strain gauge was bonded to the buccal surface of the teeth to measure coronal micro-strain during maximum intercuspation. Strain values were recorded in the contralateral intact teeth, the carious tooth preoperatively, after endodontic access preparation, and after post-obturation core restoration with composite resin.

Bite force was calibrated using a digital load indicator to ensure consistent physiological loading. This study uniquely documented real-time changes in tooth deformation throughout different phases of endodontic treatment under actual clinical conditions. The results provided novel clinical insights into the biomechanical effects of single-sitting endodontic procedures and underscored the importance of restorative approaches that enhance structural reinforcement in treated teeth.