Clinical study of application of intra-oral maxillary protractor in treatment of Class III malocclusion

Abstract

Objective The aim of this study was to evaluate the skeletal and dentoalveolar changes achieved by a tooth-borne maxillary protractor in growing skeletal and dental Class Ⅲ patients and to compare these changes with maxillary protraction face mask group.Methods Twenty patients were selected and treated with repetitive rapid palatal expansion and constriction for 7 weeks.The patients were divided into two groups according to the treatment type:the intra-oral protractor group (mean age 10.12± 1.81 years,n=10) and the Delaire type maxillary protraction group (mean age 11.02±1.08 years,n=10).In group one a tooth-borne maxillary protractor was used until anterior crossbite was corrected and then followed by wearing face mask protraction at night time.In group two,maxillary protraction face mask was required to wear at least 14 hours/day.Results Significant changes in ANB and overjet were noted in the both groups and demonstrated the effects of the appliances in the treatment of Class Ⅲ malocclusions.In comparing the two groups,the improvements were greater in the intra-oral protractor group (P＜0.05).The duration for the correction of crossbite was reduced significantly in group one (2.3 months on average) than that in group two (8.6 months on average,P＜0.001).Conclusions The combination use of an intra-oral protractor is effective for correction of skeletal Class Ⅲ malocclusion. Key words: Class Ⅲ malocclusion; Rapid palatal expansion; Repetitive rapid palatal expansion and constriction; Intra-oral protractor; Maxillary protraction face mask