Study Of Labial Alveolar Bone Thickness Of Adult Patients With Angle Class ? Malocclusion In Upper Incisors With CBCT

The alveolar bone around the root is one of the important structures of periodontal supporting tissue.Its thickness and height determine the morphological characteristics of alveolar bone,thickness and height decrease will affect the movement way and movement range of teeth during orthodontic treatment.The goal of orthodontic treatment is to be function,stability and beauty.in order to achieve this goal,the root must be in the center of the base bone.The ideal incisor position has important role for maintaining the normal occlusion of the anterior teeth,the stability of occlusion relationship of the posterior teeth,and the appearance of the facial beauty,so whether it's for function or beauty,the thickness of alveolar bone should be evaluated before treatment,and the movement of root in supporting bone tissue was accurately controlled during orthodontic treatment,avoiding root absorption,gingival retraction,bone dehiscence,bone fenestration and other adverse reactions.Objective:The purpose of this study is to measure the labial alveolar bone thickness at different sites of adult patients with Angle class II malocclusion in upper incisors with CBCT,in order to provide a theoretical basis for the control of the range and direction of tooth movement during orthodontic treatment.Methods:The sample consisted of 100 adult patients with Angle class?malocclusion: Angle class?division 1 malocclusion 50 patients(average age: 22.21±2.64 years);Angle class ? division 2malocclusion 50 patients(average age: 22.41±2.94 years),with 50 normal occlusion volunteers(average age: 22.31±2.84 years)were used as the control group.CBCT images were taken before orthodontic treatment,and then imported the acquired CBCT image data into the Invivo 5.0 image processing software for 3D reconstruction,measuring the thickness of the alveolar bone on the maxillary labial side on the sagittal plane of the tooth body,and then calculating the percentage of labial alveolar bone thickness to the total alveolar bone thickness,Statistical analysis was carriedout to differences among the three groups.Results:1.The results of cephalometric analysis showed that the age,Sex composition ratio,?SNA,?SNB,? ANB had no statistical difference among the three groups(P > 0.05).The U1-NA(mm),U1-NA(°)in Angle class?division 1 malocclusion group were the largest,in the Angle class II division 2 malocclusion groups were the lowest,the difference was statistically significant(P<0.05).2.The labial alveolar bone thickness and the percentage of labial alveolar bone thickness to the total alveolar bone thickness in left and right symmetrical teeth of maxillary incisors had no significant difference(P >0.05),among three groups;The alveolar bone thickness of maxillary central incisors was statistically greater than the lateral incisors(P<0.05);along the long axis of the tooth(from the neck to the apical direction),labial alveolar bone thickness was thinner in the middle and largest in the apex.3.The thickness of labial alveolar bone at different sites was the largest in individual normal occlusion group,followed by Angle class? division 1 malocclusion group,and the smallest in Angle class?division 2 malocclusion group;however,in the apical position,The labial alveolar bone thickness was the largest in Angle class ? division 1 malocclusion group,followed by individual normal occlusion group,and the smallest in Angle class ? division 2 malocclusion group.Conclusion:The labial alveolar bone thickness in upper incisors was related to the type of malocclusion.The labial alveolar bone thickness was less than 2 mm except in the apical area of central incisor.The percentage of alveolar bone thickness to total alveolar bone thickness was less than 20%.Therefore,before orthodontic treatment begins,the thickness of alveolar bone around the root should be carefully analyzed by CBCT,especially in class?division 2 malocclusion group,the limitation of alveolar bone should be carefully considered when the maxillary incisors were intruded,and then determine the way of teeth movement and the amount of movement to avoid periodontal tissue damage.