Radiographic Study Of Bifid Mandibular Canals Using Cone-beam Computed Tomography

ObjectiveThis study was performed to investigate the incidence and configuration of the bifid mandibular canal(BMC) in a C hinese population by using cone-beam comp uted tomography(CBCT) imaging techniques in order to provide the reference data for oral surgeon and reduce the damage of mandibular canal during the surgery.MethodsCBCT images of 815 patients(409 male and 406 female) at the second clinical medical college, Jinan university, Shenzhen people’s hospital dental medical center between June 2011 to June 2014 were retrospectively studied by New Tom VG CBCT(Qualitative Radiology s.r.l,Verona, Italy). Image analysis was performed by using NNTViewer software(Qualitative Radiology s.r.l,Verona,Italy) for evaluating the incidence and distribution of the BMC,classifying the types of BMC, observing the relation between BMC to lower third molar and measuring their diameter, length and angle. Statistical analysis was performed by using the chi-squared test and one-way analysis of variance(ANOVA) for the collected data. ResultsBMCs were found in 205 of 815 patients with an incidence of 25.15 %. 98(47.80 %) BMCs were observed in 409 males and 107(52.2 %) in 406 females. There was no significant difference between genders((P>0.05). A total of 322 BMCs were found in 205 patients with BMC. 117 cases had BMCs in bilateral mandible and 88 cases in unilateral mand ible. Four types of BMC were identified according to their course direction. The most frequently encountered type of BMC in 205 patients was the type III(forward canal type, n=117, accounting for 36.4 %), followed by the type I(retromolar canal type, n=77, accounting for 23.91 %), the type IV(buccolingual canal type, n=76, accounting for 23.6 %) and the type II(dental canal type, n=52, accounting for 16.5 %). The mean diameter of BMCs was 1.51 mm and that of the main mandibular canal was 3.15 mm. There was no any significant difference among the mean diameter of each type of BMC. The mean length of BMCs was 10mm(range: 6.07-13.23 mm). The mean superior angle between the main canal and superior wall of BMC was 145.11°, and the mean inferior angle between the main canal and inferior wall of BMC was 36.80°. Eighteen percent of BMC was adjacent to the mandibular third molars. ConclusionsBMC is not uncommon in Chinese and has an incidence of 25.15 % as indicated in the present study. The type III of BMC is the most common. Sixty- two percent of BMC is adjacent to mandibular third molars. It is suggested that a CBC T examination be recommended for detailed evaluation of the local anatomical structure before mandibular surgery to decrease the occurrence of complication.