[Morphological characteristics of the mandibular first premolars in people from Pearl River Delta region in Guangdong province].

Objective: To investigate the morphological characteristics of the mandibular first premolars in people from Pearl River Delta region in Guangdong province using three techniques, including periapical radiographs, the radiographs with files inserted the canals and the clearing technique.

Methods: A total of 363 extracted mandibular first premolars were collected and numbered. Two preoperative radiographs were taken in buccolingual and mesiodistal directions respectively.