[Physical morphology of the root canal taper in the apical region of human permanent first molars].
OBJECTIVE
To investigate the physical morphology of the root canal taper in human maxillary and mandibular permanent first molars.


METHODS
Forty maxillary and 44 mandibular extracted human permanent first molars were investigated. The roots were dissected transversely from their apical foramen vertical to the long axis of the root, and 1-mm-thick serial sections were made. The root apex side of each section was observed with a stereomicroscope at 30 x magnification. The maximum and minimum canal diameters were measured at 0, 1, 2, and 3 mm from the apical foramen. The physical canal taper in the apical section was calculated.


RESULTS
47.5%-60.0% of the narrowest diameter of root canals were present at the foramen, and 25.0%-42.5% located at the level of 1 mm from apical foramen. Almost all physical configurations of root canals in 3 mm apical region showed a bottleneck-like taper. Canal diameters increased rapidly at 1-2 mm with the biggest taper, and the taper had a bigger variance (0.07-0.35). The ring of shrunken bottleneck was formed at the level of 1 mm from apical foramen. The taper of canal in maximal diameter was larger than the one in minimal diameter.


CONCLUSIONS
The physical morphology of bottleneck-like taper in apical canal was helpful to locate the canal apical stop in root canal treatment.
Department of Cariology and Endodontology, Peking University School and Hospital of Stomatology, Beijing 100081, China. kqlinyue@bjmu.edu.cn
Lin
L
Yue
Yi
Y
Han
D000328:Adult; D003786:Dental Pulp Cavity / Q000033:anatomy & histology*; D019229:Dentition, Permanent; D005260:Female; D006801:Humans; D008297:Male; D008334:Mandible; D008437:Maxilla; D008963:Molar / Q000033:anatomy & histology*; D019227:Tooth Apex / Q000033:anatomy & histology*