| Objective By applying the cone beam CT(CBCT)technique,the changes of periapical alveolar bone height and labial/palatal alveolar bone thickness of maxillary central incisors in Angle Class Ⅱ division 2 patients before and after orthodontic treatment were investigated,aiming to analyze the intrinsic connection between the labial inclination of their maxillary central incisors and labial/palatal alveolar bone thickness,so as to explore the relationship between maxillary central incisors and facial facial aesthetics,and to provide orthodontists with some clinical reference in the process of clinical orthodontic treatment to achieve In this way,the relationship between the maxillary central incisors and facial aesthetics can be explored to provide clinical reference for orthodontists to achieve oral function and facial coordination during clinical orthodontics.Methods Among the patients with malocclusion who visited our dentistry department between October 2020 and October 2022,60 patients with Angle Class Ⅱ division 2malocclusion were selected,including 30 males and 30 females with an average age of 22.5years;30 patients with normal malocclusion were selected in the control group,including 10 males and 20 females with an average age of 23.6 years;and all of them were Han Chinese aged 18-30 years all were Han Chinese aged 18-30 years old.Before the CBCT scan,all study subjects were informed of the purpose and content of the experiment,and the shooting was completed and informed consent was signed at a certain time and under the same conditions.All the above measured values were statistically analysed using SPSS 22.0statistical software and Pearson correlation analysis was performed on the thickness of the left maxillary central incisors at different inclinations to investigate the relationship between it and the labial inclination.The measurements were(1)MH(mm);(2)DH(mm);(3)BH(mm);(4)LH(mm);(5)M-CEJ(mm);(6)D-CEJ(mm);(7)B-CEJ(mm);(8)L-CEJ(mm);(9)BL1(mm);(10)BL2(mm);(11)BL3(mm);(12)LL1(mm);(13)LL2(mm);(14)LL3(mm);(15)∠U1-SN(°);(16)∠U1-PP(°).All the above measured values were statistically analyzed with SPSS22.0 statistical software,and Pearson correlation analysis was performed on the thickness of maxillary central incisors with different inclinations to investigate the relationship between it and labial inclination.Results(1)Comparison of alveolar bone heights: both proximal/distal and labial/palatal alveolar bone heights decreased after treatment and there was a significant difference between pre-and post-treatment comparisons(P<0.05);(2)Comparison of alveolar bone attachment heights: the proximal/distal and labial/palatal alveolar bone attachment heights increased after treatment,indicating a decrease in the alveolar crest apex,with a significant difference between pre-and post-treatment comparisons(P<0.05);(3)Comparison of alveolar bone thickness: the labial cervical 1/3,root middle 1/3 and apical thicknesses increased after treatment,and there was a significant difference(P<0.05)before and after treatment;the palatal cervical 1/3,root middle 1/3 and apical thicknesses decreased,and there was a significant difference(P<0.05)before and after treatment;(4)Gender comparison of three-dimensional bone volume changes in alveolar bone: there was no significant difference(P>0.05)between genders on the change in periapical alveolar bone volume of maxillary central incisors before and after orthodontic treatment in patients with An Ⅱ~2 category;(5)Comparison of the morphology of the alveolar bone of Angle Class Ⅱ division 2 with that of normal dentition after treatment: there was a significant difference in the morphological changes of the periapical alveolar bone of the maxillary central incisors after treatment(P<0.05);there was no significant change in the labial inclination of the maxillary central incisors after treatment,and there was no significant difference(P>0.05);(6)Correlation analysis: The inclination of maxillary middle incisors ∠U1-SN and ∠U1-PP were positively correlated with the root neck 1/3,root 1/3 and apical alveolar bone thickness(P<0.05);It was negatively correlated with the thickness of the alveolar bone in the middle 1/3 of the palatine lateral root and the apical root(P<0.05).Conclusion(1)The tops of the periapical alveolar crests of the Angle Class Ⅱ division 2maxillary central incisors that have undergone non-extraction orthodontic treatment have all undergone reduction,i.e.alveolar bone resorption,and the degree of resorption varies from site to site;(2)Gender had little effect on the amount of periapical maxillary mesial incisor bone before and after orthodontic treatment in patients in the Angle Class Ⅱ division 2category;(3)A strong association exists between the labial inclination of the maxillary central incisors and the thickness of the labial/palatal alveolar bone in Angle Class Ⅱ division 2malocclusion;(4)There are significant differences in the morphological changes of the alveolar bone in Angle Class Ⅱ division 2 patients after orthodontic treatment compared to normal occlusion patients,but there are uniform criteria for the harmonization of the labial inclination and facial shape of the maxillary central incisors;(5)The above prompts us to exercise strict clinical control over the choice of orthodontic appliances,the control of incisal torque and the amount and manner of force applied.Therefore,the best orthodontic solution for the treatment of patients with Angle Class Ⅱ division 2 should be formulated in relation to the patient’s periapical alveolar bone situation and given the appropriate orthodontic force,thus preventing medically induced alveolar bone loss and at the same time restoring a stable occlusal relationship and a good facial shape to the patient. |
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