[Root fracture in endodontically versus nonendodontically treated posterior teeth: the cone beam computed tomography...

This study aimed to investigate the clinical and cone beam computed tomography (CBCT) characteristics of root fractures in endodontically versus nonendodontically treated posterior teeth.

A total of 340 posterior teeth from 305 patients were retrospectively collected. The fractured teeth were divided into endodontically treated (ET) teeth and nonendodontically treated (NET) teeth. The clinical information (age and gender of patients) was recorded. The type of fractured tooth, fractured root, orientation of fracture lines (vertical, horizontal, oblique, and irregular), direction of vertical fracture lines, location of horizontal root fractures, and bone resorption around fractured roots were evaluated and recorded based on CBCT images.

1) The distribution of teeth was significantly different between NET and ET teeth (P=0.028). Root fractures predominantly occurred in mandibular and maxillary molars. However, the proportion of premolars was significantly higher in ET teeth (27.2%) than in NET teeth (14.2%). 2) We observed a significant difference in root distribution between NET roots and ET roots (P=0.037). The mesial roots of mandibular molars were the most common fractured roots in NET and ET roots (36.4% in NET roots and 32.2% in ET roots); however, the second most common roots were the palatal roots of maxillary molars in NET roots (23.0%) and the maxillary premolar roots in ET roots (20.3%). 3) A statistically significant difference in the orientation of root fractures was observed between the two groups (P<0.001). Vertical root fractures accounted for only 43.6% of all root fractures in NET root fractures, whereas they accounted for 75.6% in ET root fractures. 4) For vertical root fractures, the direction of fracture lines between NET and ET root fractures was not significantly different (P=0.58), with both types predominantly presenting as buccal-palatal fractures (86.0% and 84.1%). 5) No significant difference was observed in the location of horizontal fractures between NET and ET root fractures (P=0.132), and the most common site was the cervical third of roots. 6) Bone loss around fractured lines significantly differed between NET and ET root fractures (P<0.001). Around 59% exhibited obvious bone loss around fractured roots in NET root fractures, whereas 91.8% of fractured roots presented bone loss in ET root fractures.

The NET root fractured teeth and ET root fractured teeth presented quite different clinical and CBCT characteristics. The complex and diverse traits of NET root fractured teeth indicate the influence of multifaceted occlusal factors in their occurrence. By contrast, ET root fractured teeth demonstrate high uniformity, indicating that their occurrence may be related to the structural changes caused by endodontic treatment.