Following an initial worsening of the Class II molar relationship as a result of straight-wire appliance effects, Forsus appliance treatment initiated during cervical vertebral maturation status (CS) 3-4 elicits more effective and efficient correction of Class II molar relationships than when initiated during CS 5-6. Data support that these effects are due mainly to maxillary skeletal and dentoalveolar restraint during a period of more rapid mandibular growth.

Intro: The goal of this thesis was to compare the skeletal and dental effects of the Forsus™ appliance observed on patients during peak growth versus post peak growth. The hypothesis was established that patients undergoing Class II treatment with a Forsus™ appliance during peak growth velocity would experience a larger degree of skeletal change than that observed in patients undergoing treatment with the same appliance, who have completed peak growth. Methods: A sample of 54 Class II patients who were consecutively treated with the Forsus™ appliance was selected for this retrospective study. The subjects were placed into peak and post-peak growth groups based on their cervical vertebral maturation (CVM) status as determined from a lateral cephalogram taken at the initiation of Forsus™ therapy. Superimpositions of initial, pre-Forsus™, post-Forsus™, and final cephalometric radiographs were completed for each patient, allowing the measurement of observed changes during 3 treatment phases for each patient. Each cephalometric radiograph was manually traced, superimposed on successive time-points and subjected to Pitchfork analysis to demonstrate changes contributing to correction of Class II skeletal and dental relationships. Results: Upon initial measurements; neither group was found to have a more severe skeletal Class II relationship. There were no significant differences between either group during Treatment Phase 1 of alignment and leveling with both groups showing a small initial increase in Class II severity. During Treatment Phase 2 with the Forsus ™ vi appliance, patients within the peak growth group showed a significantly higher mean apical base change and molar change towards Class II correction than patients who had completed peak growth. In addition, those patients also showed a significantly higher rate of apical base and molar change. Both groups showed a significantly higher A-P change during Treatment phase 2 in comparison to Treatment phases 1 and 3. There were no significant differences between either group during Treatment Phase 3 (detail/finishing) which showed a minimal trend toward relapse. Conclusions: Within the parameters of this study design, the results support that the use of the Forsus™ appliance during peak growth provides a more effective and efficient skeletal and molar change towards Class II correction.