Objective This study investigates the morphology and root canal system of premolars. Methods A total of 190 permanent premolars were collected from subjects in Lanzhou:54 maxillary first premolars, 46 maxillary second premolars, 50 mandibular first premolars, and 40 mandibular second premolars. Vernier was used to measure the length indexes. Macrography was used to observe the morphology of roots, and the cone beam CT technique was used to investigate the root canal systems. The data were analyzed by using SPSS 13.0. Results The anatomic data of the permanent premolars and root canal systems of the subjects from Lanzhou were obtained. All indexes were assumed to have a normal distribution, e.g., root length and tooth length varied. The major root canal types of the permanent premolars are types Ⅰ and type Ⅳ. Conclusion Results showed that the anatomy of permanent premolars is wholly stable, but the lengths of the teeth and root are not. Hence, caution should be observed when operating on these teeth.
