OBJECTIVETo investigate the incidence of the second mesiobuccal canal (MB2) in the mesiobuccal root of the maxillary first and second molars in Chinese population using three techniques, including the clearing technique, spiral CT scanning and serial root sections.

METHODSA total of 216 extracted human first and 334 second maxillary molars were randomly divided into two groups respectively: group A and B. The teeth in group A were cleared. The specimens in group B were subjected to spiral CT scanning, and then the roots were cross-sectioned every 1 mm from the root apex. Under the Dental operating microscope (DOM), the incidence of MB2 were recorded.

RESULTS(1) The incidence of MB2 in the first and the second maxillary molars were 81.48% and 49.70% respectively by clearing, and 77.78% and 47.31% from S-CT scanning, 88.89% and 53.89% respectively from serial root section. The occurrence of MB2 in maxillary first molars was statistically higher than in maxillary second molars (P < 0.05, chi square test). (2) There was no significant difference among the three approaches for detecting the MB2 canal (P > 0.05, chi square test).

CONCLUSIONSBoth the maxillary first molars and the second molars have high incidence of MB2.