Role of the horizontal activator in class II i malocclusion treatment

Background: The conflict in opinions about the dental and skeletal changes induced by class II malocclusion activator therapy is still present. The aim of this study was to assess the skeletal and/or dental outcomes of treating moderate-severe skeletal class II division 1 malocclusion by the activator. Materials and Methods: The sample consisted of pre and post treatment records (cephalometric radiographs) of 11 Iraqi adolescent patients (7 females 10-11 years old, and 4 males 12-13 years old). Results: The results showed significant skeletal and dental changes that reflected significant improvements in the cardinal features of class II (overjet, overbite, ANB angle, and lower anterior facial height). Conclusion: Correction of the overjet, overbite, and ANB angle in moderate-severe skeletal class II i cases by the activator into normal range values may be at the expense of unfavorable lower incisors proclination and ii angle which are very important for stability of treatment result. The activator can induce skeletal changes that reflect improvements in the antero-posterior and vertical relationships of class II i malocclusion (downward and forward growth of the mandible, remodeling of glenoid fossa, in addition to the rotation of maxillary and mandibular bases). Acrylic loading and acrylic trimming done in the activator are responsible for the dramatic dental changes that can sometimes contribute to the skeletal improvements (extrusion of lower posterior teeth, relative intrusion of incisors, overjet and overbite correction, and changing positions of points A and B). Keywords: Skeletal class II, horizontal activator, myofunctional appliance. (J Bagh Coll Dentistry 2008; 20(1) 95- 100)