CBCT Analysis Of The Relationship Between Mandibular Third Molars And Inferior Alveolar Canal In Korean And Han Adults In Yanbian Area

Objective: CBCT analysis of the differences in the positional relationship between the mandibular third molars and the inferior alveolar canal in Korean and Han adults,and to provide a basis for preoperative risk assessment.Methods: The CBCT imaging data of 260 Korean and Han Chinese patients admitted to the Department of Stomatology of The Affiliated Hospital of Yanbian University from October 2019 to May 2021 who showed contact or overlap between the root of mandibular third molars and the inferior alveolar canal on panoramic radiograph were collected.Gender,age,impacted type,impacted depth,relative position of mandibular third molars and inferior alveolar canal,shortest distance,shape of inferior alveolar canal at root tip,and cortical bone condition were recorded.Finally,the obtained data were subjected to statistical analysis.Results:1.In The Korean and Han,mesioangular impaction were dominant(45.2%,37.6%),followed by horizontal impaction(33.7%,37.6%)and vertical impaction(16.3%,19.7%).There was no significant difference between the Koreans and the Hans(P>0.05).2.The relative positions of the inferior alveolar canal and the mandibular third molars are different between the Korean and the Han.The ratio of the inferior alveolar canal in the Korean nationality on the buccal side of the mandibular third molar is 20.7%lower than that in the Han,which is 32.9%,and the proportion of the inferior alveolar canal in between the roots was 14.4% higher than that of Han 5.2%,the difference was statistically significant(P<0.05).When the inferior alveolar canal was located on the lingual and between the roots of the mandibular third molar,the rate of cortical bone disruption was higher than that on the below the roots and buccal sides,and the difference was statistically significant(P<0.05).However,in the same positional relationship,there was no difference in the rate of cortical bone disruption between the Korean and the Han(P>0.05).The ratio of Korean in between the roots side in mesioangular and horizontal impaction was higher than that in Han,and the difference was statistically significant(P<0.05).The proportion of Han in lingual side was higher than that of Korean,and the difference was statistically significant(P<0.05).When the mesioangular and horizontal impaction were located on the buccal side,the shortest distance of the Korean was smaller than that of the Han,and the difference was statistically significant(P<0.05).3.The inferior alveolar canal in the Korean and Han was mainly round/oval when it was located below the roots of the mandibular third molar(71%,78.7%),and it was mainly round/oval when it was buccal(46.5%,64.3%),the lingual side was mainly dumbbell shape(78.6%,68.4%),and the between the roots was mainly dumbbell shape(73.3%,54.5%).There was no difference in the distribution of inferior alveolar canal shape in different positions between Korean and Han(P>0.05).The rate of cortical bone disruption was higher when the inferior alveolar canal was dumbbell shaped,and there was no difference between the Korean and Han nationalities(P>0.05).4.The rate of cortical bone disruption in the inferior alveolar canal in the mandibular third molar region of the Korean was 55.8% higher than that of the Han 48.4%,but there was no difference between the Korean and the Hans(P>0.05).The risk of cortical bone disruption in the Korean was 1.980 times higher than that in the Han,and the difference was statistically significant(P<0.05).There was no difference between Korean and Han in the risk of cortical bone disruption in vertical impaction,mesioangular impaction,different impacted depths and different root numbers(P>0.05).Conclusion: There are some differences in the position of the inferior alveolar canal and the rate of cortical bone disruption in the mandibular third molar region of the Korean and Han in Yanbian,which should be paid attention to in clinical practice.