Abstract:

Objective To investigate the morphological characteristics of the mandibular first premolars in people from Pe 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．After access opening，the files were placed in the canals an d two other radiographs were taken．The mandibular first premolars with multi-canal system were selected and observed under dental operating microscope(DOM)．Th e mandibular first premolars were made transparent and were categorized using the Vertucci S classification．Results There were diferent results among the three approaches．Periapical radiographs could be used to distinguish only between one and multiple canals systems．The incidence of multiple canals was 33．33％ from the radiographs with file．Th e man dibular first premolars had a high frequency(34．44％) of multi-canal system by clearing method．Th e root canal morphology of the mandibular first premolars showed great variance．The canal orifices of the mandibular first premolars with one or two canal distributed in a buccolingual line．Th e floor of pulp chamber of the mandibular first premolars with three or four canals was a plat form．Conclusion Th e mandibular first premolars have a high frequency multi—canal system and could be classified in many categories．Using DOM an d radiographs with file is a useful way in judging the canal numbers and categories．