Measurement And Analysis Of Mandibular Canal In Mandibular Ramus In Adults With Different Sagittal Skeletal Pattern By Cone-beam Computed Tomography

Objective:The purpose of this study is to investigate the position and course of the mandibular canal through the mandibular ramus in adults men and women with different sagittal skeletal pattern by using cone-beam computed tomography (CBCT), and also to find the anatomical difference of the mandibular canal in the rami,which provides a reference basis for the design of the sagittal split ramus osteotomy(SSRO),and may reduce injuries to the inferior alveolar nerve.Methods:CBCT data of 300 Chinese adults were selected according to the inclusion criteria.These adults underwent CBCT examination from September 2014 to September 2015 in Affiliated Stomatology Hospital of Kunming Medical University, aged from 18 to 35 years old. Divided into three sagittal skeletal pattern groups according to the ANB Angle.Samples were randomly selected from each group.Class Ⅰ include 13 cases of male and 12 cases of female, class Ⅱ has 28 cases in which male and female both 14 cases, class Ⅲ include 13 cases of male and 12 cases of female. Data were measured on 3-mm-thick slices taken from a base plane at the mandibular foramen to 12 mm below the base plane. The measurement included: diameter of the inner mandibular canal(ID); thickness of mandible through the center of mandibular canal(BL); thickness of buccal and lingual cortical bone(BC and LC); The bone marrow space between the outer canal and both the buccal and lingual external cortical bone(BP and LP). All measurements were analyzed with SPSS 17.0. The statistical methods used in this study are independent samples t test, One-way ANOVA and multiple comparisons, and p value less than 0.05 was considered a statistically significant difference.Results:1. In different gender, ID, BL, BP values showed difference, which was statistically significant (p<0.05).2. In different group,BP values showed statistically significant difference for the plane 2,3 and 4.3. The diameter of the inner mandibular canal (ID) showed a trend of decrease from mandibular foramen to below in skeletal class Ⅰ and Ⅲ adults, but the ID value of class Ⅱ group showed an increasing trend at the plane 3. The thickness of mandible through the center of mandibular canal (BL) showed an increasing trend from plane 0 to plane 4, and the width of buccal bone marrow cavity(BP) showed a trend of decrease first and then an increasing trend at the plane 3, whether which kind of sagittal skeletal pattern is.Conclusions:1. The width of buccal bone marrow cavity(BP) showed a trend of decrease first and then an increasing trend in the mandibular angle area, whether which kind of sagittal skeletal pattern is. So it is more likely to injure the mandibular canal in the mandibular angle area.2.The width of buccal bone marrow cavity(BP) of skeletal class Ⅰ and Ⅲ adults is significantly narrower than that of skeletal class Ⅱ adults. So the risk of neurosensory disturbance of skeletal class Ⅰ and E1 adults is higher than that of skeletal class Ⅱ adults when been performed the SSRO.