RESUMO
PURPOSE: Primary objective of the study is to quantify and evaluate the skeletal and dental contributions during sagittal Class II correction with the Forsus™ fatigue resistant device (FRD; 3M Unitek Corp., Monrovia, CA, USA). Secondary objective is to evaluate the overall vertical, soft tissue and chin-throat relation changes with the Forsus™ appliance. PATIENTS AND METHODS: A retrospective sample of 27 Class II patients treated with the Forsus™ FRD appliance was compared to 20 untreated control subjects who were matched according to age and craniofacial morphology. Pre-Forsus™ (T0) and Post-Forsus™ (T1) cephalograms were subjected to composite cephalometric analysis. Growth changes were subtracted from the treatment changes to obtain the treatment effects of the appliance. The data were analyzed using Student's ttest and independent t test. RESULTS: Significant differences were found between the treated and the control group in 16 of 29 measured variables. The overjet and molar relation improved by 4.23â¯mm and 4.49â¯mm, respectively. This was mainly achieved by backward movement of maxillary incisors (1.4â¯mm) and molars (1.22â¯mm) and forward movement of mandibular incisors (2.26â¯mm) and molars (2.70â¯mm). Overbite decreased by 2.24â¯mm with no changes in mandibular and nasal plane angles. CONCLUSION: The Forsus™ FRD was effective in correcting Class II malocclusion mainly at the dentoalveolar level. The net skeletal and dentoalveolar contributions towards both overjet and molar correction was 13% and 87%, respectively. The improvement in soft tissue profile and chin-throat configuration was statistically insignificant.