| Objective:To analyze the changes of the root and alveola r bone of the upper anterior teeth after extraction and a dduction of t he adult classⅡ~1 patients with CBCT,so as to provide theoretical basis for the design of clinical correction scheme and minimize the iatrogenic injury.Method:12 adult patients with class Ⅱ~1 were selected for Invisalign stealth correction.In all cases,the first premolar and the second premolar were extracted.The procedure of adduction was designed to remove the canine first and then adduct the anterior teeth as a whole.The adducti on process was supplemented by micro implant nail and class Ⅱ tractio n.In the process of orthodontic treatment,the anterior adduction of th e upper anterior teeth was determined as t0 stage,and the stable one month after the end of orthodontic treatment was determined as T1 stage.CBCT was taken in t0 stage and T1 stage r espectively,and the relevant indexes of the three-dimensional data of C BCT were measured and statistically analyzed.The measurement indexes include the amount of adduction of the upper anterior teeth,the length of the root of the upper anterior teeth,t he thickness of the alveolar bone on the lip and palate side of the uppe r anterior teeth and the height of the alveolar bone.All the data are taken as the final measurement value by mys elf after repeated measurement.Results:(1)The adduction of upper and middle incisors:the adduction of crown and palate(4.697±1.285mm),t he adduction of root and palate(3.596±1.114mm);(2)The absorption of anterior teeth:the root absorption of the central incisor was(0.605±0.190mm),the lateral incisors was(0.496±0.200mm),the canine was(0.458±0.300mm),the difference of root length before and after treatment was statistically significant(P<0.05);(3)The thickness of alveolar bone in the upper anterior teeth:1/3 in the neck and 1/3 in the root,the thickness of alveolar bone in the labial side increased,the difference was not statistically significant(P>0.05),the thickness of a lveolar bon e in the palatal side decreased,the difference was statistically significant(P<0.05).1/3 of the apices of the upper anterior teeth and the thickness of the labial alveolar bone decreased,the difference was statistically significant(P<0.05),increased thickness of alveolar bone on palatal side,there was no significant difference(P>0.05);(4)The height of the alveolar bone of the upper anterior teeth:after the treatment,the height of the alveolar bone of the labial and palatal sides of the upper anterior teeth decreased,There was no significant difference in l abial side(P>0.05),the difference of palatal changes was statistically significant(P<0.05);(5)Correction time:all pati ents from the beginning of t0 period to the end of correction stable one month T1 period,the average time was(27.583±1.498)months.Conclusion:(1)In the case of extractio n of class Ⅱ~1,the root resorption of the upper anterior teeth appeared in differen t degrees before and after adduction;(2)In the case of extraction of class Ⅱ~1 teeth,the alveolar bone in the upper anterior teeth before and after adduction,bone remo deling and bone absorption were carried out at the same time,but bone absorption was the main part,the amount of bone remodeling was not large,especially the risk of bone fenestration and bone cracking existed in the palatal side and labial side of the apical area of the upper anterior teeth,the greater the distance of tooth movement,t he greater the risk. |
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