Clinical analysis on the root fracture of the maxillary first molar.

Objectives: This study aimed to investigate the common types and directions of root fractures of the maxillary first molar and the influence of root canal treatment on the prevalent sites of root fractures.

Methods: A total of 274 maxillary first molars with root fractures diagnosed via cone beam computed tomography were included. The root fractures of nonendodontically and endodontically treated teeth were identified to be spontaneous and secondary root fractures, respectively.