[The effect of two different methods of rapid maxillary expansion on treatment results of skeletal Class III malocclusion patients with maxillary protraction in early permanent dentition].

PURPOSE: To evaluate and compare the effect of single rapid maxillary expansion and repetitive rapid expansion and constriction with maxillary protraction in treating early permanent skeletal Class III patients. METHODS: Twenty children with skeletal Class III malocclusion were randomly divided into two groups.Ten patients received 1 week of rapid expansion,followed by maxillary protraction(group A) and the other ten patients received 5 weeks of repetitive rapid expansion and constriction followed by maxillary protraction (group B).Cephalometric analysis was performed before and after treatment. The data was analyzed with SPSS 13.0 software package for paired t test. RESULTS: Significant changes in cranio-maxillofacial structures were observed in both groups after 6 months of treatment.Point A moved forward. SNA, ANB, UL-EP, U1-PP, SN-MP, ANS-Me/N-Me, Wit's value increased. L1-MP, LL-EP decreased. Significant differences were found in SNA,ANB,UL-EP between the two groups(P<0.05). CONCLUSIONS: The application of combined repetitive rapid expansion and constriction with maxillary protraction increases the amount of forward movement of the maxilla significantly and presents more favourable profile results in early permanent Class III malocclusion patients.