| Objective: The incidence,types and course of bifid mandibular canal(BMC)of the Zhuang population adults in Guangxi were observed by cone beam computed tomography(CBCT).The diameter,length,and angle of BMC,the distance from the beginning and the end of BMC to the buccal and lingual bone wall,and the distance from the retromolar foramen to the last molar were measured,which provide a reference for implant surgery in the molar region of mandibular and other oral surgery to reduce and avoid the concurrency due to damage to the mandibular canal and branches.Methods: From February 2018 to January 2019,a total of 483 adults patients of Zhuang nationality who were admitted to the Stomatological Hospital affiliated to Guangxi Medical University and photographed CBCT were collected.Among them,165 patients met the inclusion criteria and exclusion criteria.The BMC was observed by iCATVision image analysis software provided by CBCT.For the patients with BMC,the gender of the patient,the types of BMC,the left and right sides of the jaw and the section of the jaw where the starting point of BMC was located were recorded.The CBCT data was imported into InVivoDental 5 image analysis software to measure thelength of BMC,the diameter at the beginning of BMC,the angle formed with BMC and the trunk tube,the distance from the beginning and the end of BMC to the buccal and lingual bone wall and the distance from the retromolar foramen to the last molar.Statistical analysis was performed on the data by using statistical methods.Results:(1)The incidence of BMC: BMCs were found in 69 of 165 patients with an incidence of 41.8%,including 40.3%(25/62)in males and42.7%(44/103)in females.A total of 89 sides of mandible showed BMCs,including 45 in the left and 44 in the right.The incidence of BMC in left and right sides of jaw was 27.3% and 26.7%,respectively.No statistically significant difference was found between males and females,and between left and right sides of the jaw(P>0.05).(2)Distribution of BMC in each segment of mandible: The proportion of BMC in the ascending branch,the posterior molar and the molar region were24.7%,56.2% and 19.1%,respectively.There was no significant difference in the distribution of BMC between men and women(P>0.05).(3)Classification of BMCs: The BMCs were divided into four types according to the direction of travel: forward canal,dental canal,buccolingual canal and retromolar canal.Retromolar canal can be subdivided into five subtypes: type A1,type A2,type B1,type B2 and type C.Among all types of BMC,the proportion of forward canal was the highest(64%),and that of buccallingual canal,dental canal and retromolar canal was 3.4%,5.6% and 27%,respectively.Among all types of retromolar canal,the proportion of type B1 was the highest(75%),followed by type A1(16.6%),and no type A2 was found.(4)The diameter and length of BMC,and the angle formed with BMC and the trunk of the neural tube: The mean diameter of BMC was 1.31±0.31 mm,andthe mean length of BMC was 9.54±5.30 mm.The mean anterior angle between the branches and the trunk was 32.69±19.99°,and the mean posterior angle was147.10±21.15°.(5)The distance from BMC to the buccal and lingual bone wall: The horizontal distance from the beginning of BMC to the buccal bone wall was6.57±1.28 mm,and that to the lingual bone wall was 4.43±1.71 mm.The horizontal distance from the end of BMC to the buccal bone wall was6.99±1.48 mm,and that to the lingual bone wall was 5.35±2.08 mm.(6)The distance from the retromolar foramen to the last molar: the distance from the retromolar foramen to the third molar was 7.08±2.81 mm,and that to the second molar was 16.01±4.57 mm.Conclusion:(1)The incidence of BMC in some adults of Zhuang population in Guangxi was 41.8%,and there was no statistically significant difference between males and females,and between left and right sides of the jaw.(2)The proportion of the posterior molar area in the mandible with BMC was the highest,followed by the ascending branch area,and the molar area was the lowest.(3)The proportion of forward canal was the highest among all types of BMC,followed by retromolar canal,and buccolingual canal was the lowest.Type B1 is the most common among all types of retromolar canal,followed by the type A1.(4)The starting point of BMC was biased to the lingual side of the jaw and gradually moves to the buccal side.(5)The distance from the retromolar foramen to the third molar was 7.08±2.81 mm,and that to the second molar was12.67±4.41 mm.It was recommended that CBCT should be photographed before the mandibular alveolar surgery to assess the position and course of the mandibular canal and BMC accurately,and to avoid the occurrence of complications caused by injury of mandibular canal and branches. |
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