| Objective To explore the transverse compensation of maxillary first permanent molars in adult patients with different vertical bone types by comparing the inclination of maxillary first permanent molars,the thickness of buccal and palatal alveolar bone,the width of dental arch,the width of alveolar arch and the width of basal bone in adult patients with different vertical bone types of Angle class Ⅲ adult patients by using CBCT three-dimensional imaging technique,by comparing the inclination of maxillary first permanent molars,the thickness of buccal and palatal alveolar bone,and the width of dental arch,alveolar arch and basal bone.Quantify whether there is a sufficient biologically safe boundary between the root of the first molar and the buccal and palatal alveolar bone after compensation.The purpose of this study is to provide some theoretical basis and clinical reference for the selection of treatment plan in clinical diagnosis and treatment,the long-term stability of treatment results and the prevention of periodontal diseases during and after treatment.Methods Class III patients who were treated in the Department of Orthodontics,affiliated Hospital of Inner Mongolia Medical University from 2018 to September 2020 were selected as subjects.According to the difference of FMA of different vertical facial types,patients were divided into three groups: high angle group,average angle group and low angle group.20 patients in each group were randomly selected as subjects.A total of 60 patients were enrolled in the study.The selected population was 19 to 30 years old,with an average age of 23.1years.The CBCT taken at the first visit was studied,and the data were transmitted to the Invivo Dental5.0 system for measurement.The measurement items include:(1)FH/MP;(2)U6 Pp’-8mm PP;(3)MBb’-3mm;(4)MBb’-6mm;(5)MBb’-8mm;(6)DBb’-3mm;(7)DBb’-6mm;(8)DBb’-8mm;(9)Pp’-3mm;(10)Pp’-6mm;(11)Pp’-8mm.(12)U6W1;(13)U6W2;(14)U6W3.All the measured data in this experiment are expressed as mean standard deviation(x ±s),and the measurement parameters are statistically analyzed by SPSS 20.0 software package.The horizontal distribution of measured items among the three groups with different vertical facial types was compared by single factor analysis of variance(α = 0.05,P<0.05).The difference was statistically significant(P>0.05).Results(1)There was significant difference in the inclination of maxillary first molars between the high angle group and the average angle group and the low angle group,but there was no significant difference between the average angle group and the low angle group(P>0.05);(2).There was no significant difference in the width of dental arch and alveolar arch among the three groups(P>0.05);There was significant difference in the width of basal arch between high-angle group and low-angle group(P<0.05),but there was no significant difference between high-angle group and average-angle group and between average-angle group and low-angle group(P>0.05).(3)The measurement results of alveolar bone thickness at three sites of MBb’and Pp’ in the three groups were statistically significant,but there was no significant difference in the three sites of DBb’ among the three groups(P > 0.05).The results of MBb’ in 3mm,6mm and 8mm 6mm in 3mm and 6mm showed that there were significant differences between high-angle group and low-angle group,and between mean-angle group and low-angle group,but there was no significant difference between high-angle group and mean-angle group(P > 0.05).The results of 3mm and 6mm showed that there were significant differences between high-angle group and low-angle group,but between high-angle group and mean-angle group.Compared with the results of 8mm,there was significant difference in Pp’ between high-angle group and mean-angle group and low-angle group(P < 0.05),but there was no significant difference between average-angle group and low-angle group(P > 0.05).Conclusion 1.Class Ⅲ malocclusion The width of the basal arch in the high-angle group of deformity is underdeveloped,and the lateral compensation of the maxillary first molar is more obvious,the surrounding alveolar bone is relatively weak,and the risk of clinical correction is higher.2.In low-angle and average-angle cases,the compensation is relatively small,and the indications can be appropriately relaxed.If necessary,the compensation can be increased within the anatomical boundary to expand the dental arch to achieve the purpose of covert treatment.3.Before treatment,CBCT should be taken routinely for Class Ⅲ patients to understand the tooth compensation and biological boundary,and carefully choose the treatment plan suitable for the patient to avoid iatrogenic injury. |
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