Changes in mandibular length before, during, and after successful orthopedic correction of Class II malocclusions, using a functional appliance

Forty-seven girls were successfully treated with a functional appliance (FA). To be included in this study, the rate of increase in mandibular length during treatment had to be greater than twice the mean rate for a subgroup of 20 of these patients evaluated during a pre-FA observation period. The mean mandibular growth rate was 6 mm per year while the FA was activated. In the ensuing months, cephalograms were taken at intervals coinciding with five post-FA phases, including complete edgewise treatment and retention. During the post-FA phase of initial edgewise treatment, the mandibular growth rate was dramatically reduced when compared with 47 controls matched for age, sex, and initial SN:GoGn angle. Selected individual cases are presented to illustrate the great variability in growth responses that were obtained. This study found highly significant increases in mandibular length still present 2 years after treatment, diminished but still significant gains after 3 years, and no significant difference after 4 years.