| Objective:It is to provide a certain reference for orthodontic maxillary expansion treatment before sugery of adult skeletal Class II malocclusion patients who require orthodontic orthognathic combined treatment by measuring the thickness of the alveolar bone on the buccal and palatal sides of the maxillary posterior teeth in patients with skeletal Class II malocclusion and mandibular retraction in different vertical bone types by using cone beam CT.Method:From January 2020 to December 2021,52 patients with skeletal class II malocclusion and mandibular retraction who underwent oral cone beam CT(CBCT)were selected from the patients who visited the Affiliated Stomatological Hospital of Nanchang University.Patients with skeletal class II malocclusion and mandibular retraction all met the conditions of ∠ANB >4.7 °,∠SNB <76 °,Wits value>3mm.Referring to the Downs analysis method,the subjects were divided into high angle groups(MP-FH angle>32 °,17cases),average angle group(22 ° ≤ MP-FH angle≤ 32 °,18 cases),low angle group(MP-FHangle<32 °,17 cases).Eighteen patients with normal occlusion of skeletal class I and average angle were selected as the control group(a population with normal and coordinated dental and maxillofacial development,0.7 °<∠ANB <4.7 °,-3.6<Wits value<2mm,22 ° ≤ MP-FH angle≤32 °).It is measured the thickness of alveolar bone on the buccal and palatal sides of the right maxillary posterior teeth in each group of subjects.The measurement data was statistically analyzed using SPSS 25.0 software.Result:1.There were statistical differences in alveolar bone thickness of the right maxillary posterior teeth between the skeletal class II low-angle group,the average-angle group and the high-angle group(P<0.05),and the thickness of the alveolar bone of right maxillary posterior teeth was generally smaller on the buccal and palatine side than that in the low-angle group and the average-angle group.2.Compared with the the skeletal class I average-angle group and the the skeletal class II average-angle group,there was no significant difference in the thickness of alveolar bone of the right maxillary posterior teeth between the two groups on the buccal and palatine sides.Compared with the bony class II low-angle group and high-angle group,there were statistically significant differences in the thickness of alveolar bone of the right maxillary posterior teeth on the buccal and palatine sides(P<0.05).3.The thickness of the alveolar bone of the right maxillary posterior teeth on the buccal side gradually thickened from the first premolars to the second molar,but the trend of the palatal side was inconsistent.4.The thickness of alveolar bone on the palatine side of the right posterior maxillary teeth showed a significant increasing trend from crown to root(P < 0.001),but the change trend on the buccal side was inconsistent.5.The thickness of the alveolar bone of the right maxillary first premolar,the second premolars and the first molar’s mesial root on the buccal side was thin,the minimum value was 0mm,and the maximum value was 5.43 mm in the maxillary second molars,and the thickness of the alveolar bone of the right maxillary first molars and the second molars on the palatine side was thin at the apical level,the minimum values were 2.20 mm and 1.75 mm,respectively,and the first premolars were the thickest with a maximum value of 9.90 mm.Conclusion:1.The high-angle adult patients with the skeletal class II malocclusion,the thickness of the alveolar bone on the buccal and palatine sides of the maxillary tooth is relatively thin compared with the low-angle and average-angle patients.2.The thickness of the alveolar bone of the maxillary first premolar,the second premolars and the first molar’s mesial root on the buccal side was thin,and the thickness of the alveolar bone on the root palatine side of the maxillary first molars and the second molars was thin at the apical level... |
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