[Micro-CT study of root canal morphology of mandibular first premolars with multi-canals]

To observe root canal system of multi-canal mandibular first premolars and to analyze the morphology of them by micro-CT and three-dimensional reconstruction.

Thirty-two extracted mandibular first premolars with multiple root canals were selected and scanned by micro-CT. The number and morphology of canals, location of bifurcation and 5 subtle structures (lateral canals, apical ramification, isthmus, loops, apical delta) were analyzed.

In the 32 specimens, 96.88% contained radicular depressions or grooves. The canal configuration was type II, Ⅲ, Ⅴ: 3.12%, type Ⅳ: 31.25%, type Ⅷ: 9.38%, type Ⅸ: 15.62% and C-shaped canal: 34.38% by Vertucci's classification. 62.50% of the canals bifurcated at the middle third of roots, comparing with 37.50% at apical third. The incidence of the lateral canals, apical ramification, isthmus, loops and apical delta was 56.25%, 43.75%, 40.62%, 21.88% and 6.25%, respectively, which were all found at the middle and apical third of roots except that lateral canals were found at all depth of canals.

Most mandibular first premolars with multiple canals contain radicular depression or grooves, of which root canal system are complicated. Micro-CT can provide clear and accurate three-dimensional information of canal morphology.