CBCT Study Of The Relationship Between The Bifid Mandibular Canal And The Position Of The Mandibular Third Molar

Objective: To observe the bifid mandibular canal's incidence and morphology using cone beam computed tomography(CBCT),and to measure the relevant values.Furthermore,study the relationship between the gender,the side and the position of the mandibular third molar and the bifid mandibular canal.Methods: Cellected 703 patients' CBCT images from March 2015 to June 2019 in Shijiazhuang area for a retrospective study.These included 702 samples that fit the postion calssification of impacted mandibular third molar.Using NNT viewer image processing software,observed the bifid mandibular canal and determined type.Measured the bifid mandibular canal's length L,diameter R,the shortest vertical distance from the upper and lower edge of mandible A and B,the shortest vertical distance from buccoligual bone wall C and D.SPSS Statistics 21.0 software was used for satistical analysis.Results:1.Among 703 cases(1406 sides),the incidence of bifid mandibular canal was 41.54%,the forward canal was the most,276 sides(47.26%),followed by 248 sides(42.47%)of the retromolar canal,36 sides(6.16%)of the dental canal,23 sides(3.94%)of the bucoolingual canal,and 1 side of the trifid mandibular canal.2.There was no significant difference in the incidence of the bifid mandibular canal between males and females,left and right sides(P>0.05).3.The incidence of the bifid mandibular canal in 430 vertically impacted position of the mandibular third molar was 40.00%,in 111 mesioangularly impacted position of the mandibular third molar was 37.83%,and in 161 horizontally impacted position of the mandibular third molar was 26.09%.The incidence of the bifid mandibular canal in vertically impacted position of the mandibular third molar was higher than that in horizontally impacted position of the mandibular third molar,and the difference was statistically significant(P<0.0167).4.L=11.87±4.29 mm,R=1.26±0.41 mm,A=10.69±2.48 mm,B=18.16±4.78mm,C=6.91±1.62 mm,D=4.71±1.84 mm.Side had no effect on the measured values.Gender had effect on the bifid mandibular canal's diameter R and the shortest vertical distance D from the lingual wall of the mandible.5.The bifid mandibular canal's length L in mesioangularly and vertically impacted positions of the mandibular third molar were greater than that in horizonally impacted position of the mandibular third molar,and the difference was statistically significant(p<0.05).Conclusions: CBCT can clearly observe the mandibular nerve canal and the bifid mandibular canal,and can accurately measure the relevant values.It is the preferred method to study the bifid mandibular canal at present.The different positions of the mandibular third molar have influence on the incidence and length of the bifid mandibular canal.Gender and side have no effect on the incidence of the bifid mandibular canal.The incidence of the bifid mandibular canal in this study is high,and the experimental data in this study have guiding significance for clinical treatment.