The Evaluation Of The Clinical Effects Of Angle Class Ⅱ Division 1 Malocclusion During The Mixed Dentition By Improved Activator

Objective:Angle Class Ⅱ division 1 malocclusion classification is a common type. For the patients with mixed dentition, using functional appliances to promote the development of mandible is one of the preferred treatment plans for orthodontic doctors. We improved the traditional activator, and evaluate the clinical effects of improved activator in patients with Angle Class II division 1 malocclusion in mixed dentition. The purpose of this study was to provide theoretical guidance for the application of improved activator.Methods:21 patients (9 male,12 female, with average age of 10.0±1.0) with Angle class II division 1 malocclusion in mixed dentition stage were selected and treated with improved Activator. To improve the retention of traditional Activator, we added the buccal shield cutting edge cap, and remove the mandibular labial arch, and get improved activator. Model analysis and cephalometric analysis were performed to evaluate the clinical effects before and after treatment. The data were analyzed with SPSS 17.0 statistical software, to evaluate the changes of hard and soft tissue of patients with Angle class II division 1 malocclusion in mixed dentition stage by improved activator.Results:The improved activator is more effective than the traditional activator. Compared to the traditional activator, improved activator not only maintains the treatment effect in sagittal and vertical direction, but also stablizes transverse arch width. After treatment, the overbite, over jet reached the normal value and the profile of patients is improved. The length of mandibular ramus and body increased, the upper incisors upright, and the upper and lower lip moved backwards, and the facial convexity decreased.(1) In sagittal direction:after treatment, SNB, MP-FH angle were increased by 0.79°, 2.28°,respectively. The mandible rotated backward and downward, the upper incisors uprightly inclined and the lower incisors labially inclined. In soft tissue, upper lip angular and lower lip thickness were decreased by 3.9°,2.5mm, while upper lip length and lower lip base angular were increased by 1.29mm,1.2° respectively. It showed that the upper and lower lip moved backwards, and the facial convexity decreased. The profile of patients is improved.(2) In vertical direction:the length of mandibular ramus increased 3.5mm averagely. Anterior facial height, lower anterior facial height, posterior facial height, lower posterior facial height were increased 5.4mm,4.9mm,4.2mm,4.5mm respectively. (3) In horizontal direction:the width of upper base bone arch increased 1.02mm significantly, while the width of upper and lower arch have no significant changes.Conclusions:For the patients with Angle Class Ⅱ Division 1 in mixed dentition, the improved activator is more effective than traditional activator. The improved activator not only maintains the treatment effect in sagittal and vertical direction, but also stablizes transverse arch width. After treatment, the overbite, over jet reached the normal value. The width of upper base bone arch and the length of mandibular ramus increased, the mandibular plane rotated clockwise. The upper incisors upright, the upper and lower lip moved backwards, the facial convexity decreased, and the profile of patients is improved.