Orthodontic effects of rapid maxillary expansion combined with maxillary protraction on skeletal Class Ⅲ malocclusion during the mixed dentition
Objective To evaluate the therapeutic effect of rapid maxillary expansion combined with anterior traction on maxillary transverse deficiency in patients with skeletal Class Ⅲ malocclusion during the mixed dentition period using cone beam computed tomography(CBCT)technology.Methods A total of 19 mixed dentition patients(average age 8.47±0.70 years old)with skeletal Class Ⅲ malocclusion were selected.CBCT was taken before maxillary protraction combined with rapid maxillary expansion(T1)and 3 months after treatment(T2),respectively,to measure the inclina-tion of the first maxillary molar,the crown width and alveolar width of the first maxillary premolar,the second primary molar and the first molar,the width of the maxillary basal bone,the height of the alveolar crest and the location of the second maxillary premolar germ in the alveolar bone.The differences in various measurement items before and after treatment were compared.Results The crown width of the first maxillary premolar increased by(2.37±3.47)mm(P=0.008),the median increase in crown width of the second primary molar was 3.37mm(P=0.009)and the crown width of the first molar increased by(2.60±2.53)mm(P＜0.001)from T1 to T2.The alveolar width of the maxillary first premolar,the second primary molar and the first molar increased by(1.63±2.45)mm(P=0.010),(2.12±2.59)mm(P=0.002)and(1.98±2.10)mm(P＜0.001)respectively.The width of the apex of the palatal root and the width of resistance center of the first molar increased by(2.00±2.40)mm(P=0.002)and(2.00±2.07)mm(P＜0.001)respectively,with statistically significant differences.There was no statistically significant difference in.the tipping of the first maxillary molar(P=0.196,P=0.251),the width of the maxillary basal bone(P=0.192),the width of the mandibular basal bone(P=0.266)and the width of the center of resistance of the first molar(P=0.678),the height of the alveolar bone of the first maxillary molar(P=0.136),the second primary molar(P=0.638)and the first molar(P=0.274)and the location of the germ of the second premolar in alveolar bone(P=0.058)before and after treatment.Conclusion Rapid maxillary expansion combined with maxillary protraction can significantly improve the transverse deficiency of the middle-posterior arch and maxillary bone in mixed dentition patients with skeletal Class Ⅲ malocclu-sion.The treatment has no effect on the relative position of the premolar tooth germ in the alveolar bone.
Mixed dentitionSkeletal Class Ⅲ malocclusionRapid maxillary expansionBasal bone widthCone beam computed tomography
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