To study root morphology, the incidence of three root canals and the root canal anatomy of maxillary premolars.

The cone-beam computed tomography (CBCT) data of 779 maxillary first premolars and 728 maxillary second premolars were collected from 412 patients in Zhuhai Stomatological Hospital. The root and canal morphology, incidence of three canals, bilateral symmetry and location of root canal bifurcation were analyzed.

The incidence of three canals in the maxillary first premolars was 1.8% and that in the maxillary second premolars was 0.3%. The incidence of three canals in the maxillary first premolars was significantly higher than that in the maxillary second premolars (χ² = 8.304, P = 0.004). The symmetrical ratio of the three-canal maxillary first premolar was 27.3%. There was no symmetrical three-canal maxillary second premolar. The anatomical morphology of the maxillary premolar can be single root, double root or trident root. Its internal root canal system is complex and diverse. There are seven kinds of Vertucci morphology: the first maxillary premolar is mainly Vertucci Ⅳ type, and the second maxillary premolar is mainly Vertucci Ⅰ type. Most of the root canal bifurcations of the three-canal maxillary premolars were observed in the midthird or the cervical third of the root. All three-canal maxillary premolars had three independent apical foramens.

The root canal morphology of maxillary premolars is complex and changeable. CBCT plays an important role in the discovery of variation and extra root canals.