Influence of apical root resection level and filling technique on the fracture resistance of endodontically treated teeth: a biomechanical study.

This study aimed to investigate the influence of apical root resection level and root canal filling technique on the fracture resistance of endodontically treated teeth. Eighty mandibular premolars were selected and evenly distributed based on similar anatomical characteristics into two groups (n = 40) according to the root canal filling technique: single-cone technique and lateral compaction technique. One week after root canal treatment, each group was further divided into four subgroups (n = 10) based on the level of apical root resection: without root resection, 3 mm, 4 mm, and 5 mm. Following resection, a retrograde cavity was prepared and filled with mineral trioxide aggregate. All specimens were embedded in cylindrical acrylic molds and subjected to a fracture resistance test and fracture pattern analysis. Two-way ANOVA, Tukey's post hoc and Fisher's exact tests were performed (α = 5%). Teeth that underwent apical root resection 5 mm from the apex demonstrated significantly lower fracture resistance compared to those without root resection (p < 0.05). No differences were observed among the 3 mm and 4 mm resection groups, nor between these groups and the groups without resection or with 5 mm resection (p > 0.05). The root canal filling technique did not affect fracture resistance (p > 0.05) and the fracture pattern was similar between groups (p > 0.05). In conclusion, the fracture resistance of endodontically treated teeth decreased following a 5 mm apical root resection. The single-cone and lateral compaction techniques demonstrated comparable biomechanical performance.