Analysis On Morphological Characteristics Of Crown And Root Mandibular Central Incisors With Skeletal Class Ⅲ Malocclusion Based On CBCT

Objective:The purpose of this study is to investigate the crown-root morphology of mandibular central incisor in skeletal Class III malocclusion by cone-beam computed tomography(CBCT)and explore the characteristics of the crown-root morphology in different labial-lingual inclination of mandibular central incisor,and analyze the correlation between the crown and root morphology of mandibular central incisor and the corresponding alveolar bone morphology,so as to provide references for clinical diagnosis and treatment of orthodontics.Methods:Patients were selected randomly from those who had been received CBCT,with 15 normal patients in the control group(9 males and 6 females with an average age of 21.6 years)and 40 patients with skeletal class III malocclusion in the experimental group(23 males and 17 females with an average age of 18.9 years).Further,the experimental group was subdivided into the lingual inclination group and erection group according to different labial inclinations of the lower central incisor.The crown-root angle,crown length,root length and crown-root ratio of the mandibular central incisor and the corresponding alveolar bone morphology of the experimental group were measured.The SPSS 23.0 software was adopted for statistical analysis.Measurement data were expressed by mean ± standard deviation(χ±s).The independent samples t-tests were adopted to compare the crown-root morphology of mandibular central incisor between the control group and the experimental group,and between the lingual inclination subgroup and the erection subgroup in the experimental group.The correlation analysis between the crown and root morphology of mandibular central incisor and the corresponding alveolar bone morphology in the experimental group were tested by pearson correlation test.P<0.05 indicates a statistically significant difference.Results:1.The collum angle in the experimental group is smaller than that in the control group(P<0.01);2.In the patients with skeletal class Ⅲ malocclusion,the crown-root angle in the erection group was smaller than that in the lingual inclination group(P<0.01);the root length in the erection subgroup is longer than that in the lingual inclination subgroup(P<0.05);3.Among the patients with skeletal class Ⅲ malocclusion,the crown-root morphology was correlated with the corresponding alveolar bone morphology at different degrees(P<0.05).Conclusion:1.The crown-root angle of the mandibular central incisor is obvious in patients with skeletal class Ⅲ malocclusion,and the crown-root morphology of the mandibular central incisor is significantly different between the erection group and the lingual inclination group.2.There is a significant correlation between the crown-root morphology of the mandibular central incisor and the corresponding alveolar bone morphology in patients with skeletal class Ⅲ malocclusion.