| ObjectiveTo analyze the effect of extraoral appliance in non-extraction treatment of overjet malocclusion about the earlier period of permanent teeth.Materials and methods36 patients with overjet of classⅡdivision 1 malocclusion, who were treated by extraoral appliance and fixed appliance were chosen and divided into two groups. Each group also included two conditions. The lateral projection taken at the beginning and the end of the treatment were analyzed. To evaluate posttreatment changes by comparison of 33 pretreatment and posttreatment cephalometric tracings and 17 dental cast measurements, and to make statistical analysis. Multiple comparisons of pretreatment and posttreatment among the groups in ANOVA were also developed.ResultsPaired-sample t-test was used to analyze the measurements. Maxilla had a very significant change, but the change of mandible hadn't statistical significance except Go-Gn,N-ANS,ANS-Me and Ar-Go. The result of multiplicity shows that the change of SNA,ANB had significant change(P＜0.01),in addition, the change of U1-NA length,U1-PP angle,U1-Ptv,U6-Ptv,overjet and Upper-lip had statistical significance. Owning to the multiple comparisons, we found that the second group which included the most significance was prior to another. ConclusionPatients with overjet by non-extraction can achieve satisfactory effect. The tooth and facial soft tissue change obviously. The morphous of soft tissue has obvious correlation with the treatment of headgear. The maxillary arch lengths were also significantly increased; there were no consistent changes of the mandibular arch lengths. ClassⅡmalocclusion may be treated with the orthopedic cervical headgear. The treatment results in increased growth of the dental arch widths by expansion of the inner bow of the headgear. The widening of the maxilla is followed by spontaneous widening of the mandible.
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