Long-term effects of the Forsus Device in Class II division I patients treated at pre-peak, peak, and post-peak growth periods: A retrospective study

To assess the long-term effects of the Forsus Fatigue Resistant Device (FFRD) for the correction of Class II division 1 malocclusion during pre-peak, peak, and post-peak growth periods.

This retrospective study was conducted on 60 patients that received FFRD with concurrent full-fixed orthodontic appliances during pre-peak (n=18), peak (n=21) and post-peak (n=21) maturational stages. The FFRD groups were compared with 60 untreated Class II control subjects obtained from the University of Michigan growth study and matched by skeletal age, sex, and observation periods. Lateral cephalograms were obtained at three time-points: [T1] pre-treatment; [T2] end of comprehensive orthodontic treatment; and [T3] retention (average of 3 years in retention). Nineteen linear and angular measurements were recorded. Short-term (T1- T2) and long-term (T1-T3) treatment changes were analyzed using paired Wilcoxon Signed Rank tests.

In the pre-peak group, FFRD caused temporary restraint of maxillary growth and an increase in mandibular length at T1-T2 compared to controls. No significant differences were found at T2-T3 time points. The net changes (T1-T3) included a restraining effect on the maxilla and dentoalveolar compensation. In the peak group, maxillary restraint effect was seen at T1-T2, but this effect relapsed at T2-T3 time points. Similar to the pre-peak group, the net results (T1-T3) included maxillary headgear effect and dentoalveolar compensation. In the post-peak group, the net effects (T1-T3) of treatment included only dentoalveolar compensation.

Overall, Class II malocclusion correction with FFRD is stable at three years post-treatment and is mainly achieved by maxillary restraint and dentoalveolar compensation at the pre-peak and peak stages and dentoalveolar compensation during the post-peak stage.