The 3D Measurements Of Mandibular Canal Positioning By CBCT In Posterior Mandible

Purpose: To position the mandibular canal by using cone-beam CT in posterior mandible.These cases are collected to measure and analyze the 3D measurements of mandibular canal,and the shapes of mandible.The CT data were compared with age and gender for investigating the correlation.This study provided clinical references to help improve the mandibular surgery safety and decrease the complications of implant surgery in posterior mandible.Method and material: CBCT images of 82 patients are collected from department of radiology in Affiliated Stomatological Hospital of Fujian Medical University.All patient had undergone CBCT examination between July 2015 and May 2016,patients are divided into two groups which are youth group 50 patients(18~39 years old)and middle aged group 32 patients(40~60 years old).The data included 41 male and 41 female,the mean ages were 35.8 and 36 years old respectively.There are 16 cases which missed 1 tooth,and 4 cases which missed 2 teeth that were not consecutive in mandibular posterior area included mandibular first premolar to second molar.After the computerization and three dimensional reconstruction of CBCT scan,region of mental foramen,mandibular second premolar,first molar,second molar and third molar were found in cross sectional images.Inclusion criteria: 1.symmetrical mandible 2.without severe malocclusion 3.without mandibular malformation 4.mandibular teeth did not have severe periodontal disease Exclusion criteria: 1.mandibular canal did not include completely in any cross images2.mandibular canal were shown blurry or mental foramen was unclearly in any cross images Measurement: 1.the position of mental foramen 2.the distance from mental foramen to the alveolar crest 3.the distance from the superior aspect of mandibular canal(MC)to the alveolar crest 4.the distance from the inferior aspect of MC to the bottom of mandible 5.the distance between the buccal aspect of MC and buccal bone plate of mandible 6.The distance between the inner edge of MC and lingual bone plate of mandible 7.vertical and horizontal diameter of MC 8.the shapes of mandible 9.the shortest distance of superior aspect of MC to root apexResult: On both left and right sides of mandibular posterior area,the distances from the superior aspect of mandibular canal(MC)to the alveolar crest are(13.54±1.9)mm and(13.51±1.84)mm respectively,the distances from the inferior aspect of MC to the bottom of mandible are(9.65±1.35)mm and(9.61±1.55)mm respectively.In the sections of left and right mandibular molar,the distances between the buccal aspect of MC and buccal bone plate of mandible are(5.72±1.24)mm and(5.68±1.2)mm respectively,the distances between the inner edge of MC and lingual bone plate are(3.52±1.21)mm and(3.51±1.05)mm respectively.Conclusion: Cone-beam CT through the references of other anatomical structures can be positioning the mandibular canal accurately.And hence,the mandibular canal positioning by CBCT in posterior mandible is reliable and feasible via collecting large amounts of data and statistical analysis.