An analysis of the corrective contribution in activator treatment.

This retrospective study (1) cephalometrically investigates the effectiveness of activator therapy, (2) evaluates the contribution of skeletal growth in the self-correction of the Class II malocclusion, and (3) analyzes separately the dental and skeletal responses to activator treatment and the differences between the incisor and molar areas. The subjects, all in the mixed dentition, were selected from a single center and were divided into a group of 40 Class II patients treated with an activator and an untreated group of 30 Class II patients. Dentoskeletal changes that occurred were compared on lateral cephalograms taken before the treatment/observation period and after 21 months (standard deviation, three months). When the activator patients were compared with the untreated control subjects, therapy promoted a combination of skeletal and dental changes that led to an improvement of the sagittal discrepancy. Other changes observed in the untreated Class II subjects did not bring about a correction of the malocclusion. An analysis of the corrective contributions in activator therapy in the posterior area showed that the orthopedic effects were greater than the dental effects in correcting the posterior occlusal relationship. In the anterior area of the arch, although both the skeletal and dental changes were favorable toward the sagittal correction, the skeletal contribution was greater than the dental contribution. In general, the skeletal contribution (140%) exceeded the dental correction (60%), and the mandibular changes (73%) exceeded the maxillary contribution (27%) both in the anterior and posterior regions.