| Objectives The bifid mandibular canal(BMC)is an anatomical variation,which causes anesthetic failure and surgical accidents occasionally.This study is to observe the prevalence and anatomical location of BMCs,providing clinical value in reducing the occurrence of surgical accidents and postoperative complications.Methods CBCT images of 321 outpatients were selected as the study subjects.Observe the prevalence of bifid mandibular canals and the composition ratios of each branch type.Measure diameter of the mandibular canal,the branch diameter,the branch length,the distance from the branch to the buccal/lingual wall of the mandible,and that to the mandibular alveolar ridge.Observe the 194 dry adult mandibles from the Department of Oral Anatomy and Physiology of Tianjin Medical University.Assess the prevalence,mean diameter and mean insertion depth of retromolar foramina(RMF).Results 1.Of the 321 patients(642 sides),84(26.17%)cases of BMCs and 105(16.36%)unilateral bifurcation of hemi mandibles were observed.In unilateral mandibular samples,there were 57 cases(17.76%)of BMCs on the left side and 48 cases(14.95%)on the right side.There was no significant difference in distribution of BMCs between left and right sides(P=0.34,P>0.05).43(28.66%)patients with BMCs were males and 41(23.98%)were females.There was no significant difference in distribution of BMCs between genders(P=0.34,P>0.05).Besides,two cases of trifid mandibular canals were found in unilateral mandibles.2.The retromolar canals were the most common types(46.67%),followed by the forward canals(40.00%),the dental canals(10.48%)and the buccolingual canals(2.86%).3.Of the 321 patients(642 sides),30(9.35%)cases and 36 sides(5.31%)of RMF were observed.73.47% retromolar canals reached the bone surface and formed RMF.4.The median diameter of mandibular canals was 5.04(4.54-6.02)mm and that of branchess was 2.26(1.95-3.01)mm.The median length of branches was 13.68(10.56-18.68)mm.The median horizontal distances from the branch to the buccal wall of mandibles,to the lingual wall of mandibles and the median vertical distance to the mandibular alveolar bone ridge were respectively 5.00(3.75-6.25)mm,3.00(2.00-3.75)mm and 0.00(0.00-8.50)mm.There was a statistically significant difference between distances from the branch to the buccal wall of mandibles with the distance to the lingual wall of mandibles(P<0.001).5.Of the 194(388 sides)dry adult mandibles,23 cases(11.86%)and 29 sides(7.47%)of RMF were found in the retromolar region,including 16 cases on the left side,13 cases on the right side and 5 cases on both sides.Totally,33 RMF were found in 23 cases,but there were 3 cases where 2 foramina existed simultaneously in the same retromolar region.There was no significant difference in distribution of RMF between left and right sides(P=0.56,P>0.05).6.The mean diameter of the 33 RMF was 1.0 ± 0.3mm.The mean diameter of the left RMF was 1.0 ± 0.8mm,and the mean of the right RMF was 0.9 ± 0.6mm.There was no significant difference in the diameter of RMF on the left and right sides(P=0.15,P>0.05).Conclusion The prevalence of mandibular canal branches was 26.17%,and there was no significant difference between the sex and the left and right sides.The prevalence of the retromolar canal foramina was about one tenth,and the diameter of RMF was about 1mm.There was no significant difference in prevalence and diameter of RMF between left and right sides.The anatomical characteristics of the mandibular canal branch are relatively stable,and there is no significant difference among different age groups.CBCT is an effective method to identify the branches of the mandibular canal.CBCT examination before operation to clarify mandibular canals and branches can prevent the surgical damaging from mandibular canals and branches,and reduce various complications during and after the operation. |
