OBJECTIVETo determine the root canal initial taper of mandibular second premolars of 13-23 year-old people by using Micro-CT.

METHODS23 extracted, single root, human root canal of mandibular second premolars of 13-23 year-old people were selected. The teeth were embedded in resin. The resins were scanned using Micro-CT at a resolution of 10 microm. The photographs at each level of 1 mm perpendicular to the long axis of the tooth were chosen. Bucco-lingual (BL) and mesio-distal (MD) diameters of each canal were measured at cervical, middle and apical third of the canals. Finally the taper were calculated and analyzed.

RESULTSThe average taper of cervical, middle, and apical third of adolescents' root canals were 0.06, 0.08, 0.07 (mesio-distal direction) and 0.32, 0.21, 0.25 (bucco-lingual direction). The difference was not observed among thee level on mesiodistal direction about the canal taper by t-test (P > 0.05), but there was difference among three level on bucco-lingual direction about the canal taper by t-test (P < 0.05).

CONCLUSIONThe change of bucco-lingual taper of mandibular second premolar of 13-23 year-old people is obvious, and the smallest taper is in middle third of the canal. The mesio-distal taper of the canals is smaller than the bucco-lingual taper and the change of mesio-distal taper isn't obvious.