| Objective:Three-dimensional reconstruction of CBCT images using dental imaging software was used to study the relationship between the crown-root angulation and the alveolar bone thickness in the apical area of lower anterior incisor in adult patients with severe skeletal class III malocclusions,comparing whether there are differences in the crown-root angulation and alveolar bone thickness in patients with different vertical skeletal facial types,to provide theoretical basis and reference for orthodontic treatment of patients with severe skeletal class Ⅲ.Materials and Methods:Severe skeletal Class III malocclusion who were treated in the Orthodontics Department of Dalian Stomatological Hospital affiliated to Dalian Medical University from September 2018 to December 2020 were selected,with an average age of 22.3±4.2 years,including 28 male patients and 32 female patients cases,a total of 60 cases.According to the lateral cephalometric X-ray films and Cone-Beam Computed Tomography imaging datas before treatment,these patients were divided into hyperdivergent group(22 cases),normodivergent group(20 cases)and hypodivergent group(18 cases)according to the different vertical skeletal types,with even distribution of males and females in each of the groups.Invivo dental 5.0 software was used to reconstruct the Cone-Beam Computed Tomography(CBCT)images taken in the first diagnosis in three dimensions,and measurement was performed on the largest screenshot of the lip and tongue of the mandibular central incisor.SPSS 25.0 software was used to perform independent sample t-test on the data measured before treatment.One-way analysis of variance was used to compare whether there were statistical differences in the crown-root angulation and the alveolar bone thickness in the apical area of the mandibular anterior teeth in adult patients with different vertical skeletal facial types and severe skeletal class III malocclusion.Results:(1)At the mandibular central incisor in the severe skeletal class Ⅲ patients,the crown-root angulation in the hypodivergent group > normodivergent group >hyperdivergent group(P<0.01).(2)At the mandibular central incisor in the severe skeletal class Ⅲ patients,labial alveolar bone thickness of hyperdivergent group was narrower than that of the normodivergent group and the hypodivergent group(P<0.01);Lingual alveolar bone thickness in the hypodivergent group > normodivergent group(P<0.01),normodivergent group > hyperdivergent group(P<0.05):Total alveolar bone thickness in the hypodivergent group > normodivergent group > hyperdivergent group(P<0.01);labial alveolar bone thickness < lingual alveolar bone thickness(P <0.01)in patients with different vertical skeletal facial types in severe skeletal class Ⅲ.Conclusion:In severe skeletal Class III malocclusion patients,there is a close relationship between crown-root angulation,alveolar bone thickness in the apical region of mandibular anterior teeth and vertical skeletal facial type.The results of this study showed that the crown-root angulation of these patients gradually increased from hyperdivergent type,normodivergent type and hypodivergent type.The thickness of alveolar bone in the apical region was gradually thickened from hyperdivergent type,normodivergent type and hypodivergent type,and the thickness of the lingual alveolar bone in the apical region was greater than that in the labial alveolar bone in each group.These results suggesting that orthodontists should pay more attention to severe skeletal Class III malocclusion.For example,in the high angle group,special attention should be paid to the narrow alveolar bone thickness,while in the low angle group,greater crown-root angulation should be paid attention to when removing the lingual compensation of the lower anterior teeth.In order to avoid iatrogenic injury such as bone fenestration,bone cracking and root resorption,we should pay more attention to excessive tooth movement during orthodontic treatment of severe skeletal Class III adult patients. |
PDF Full Text Request