Mandibular changes during functional appliance treatment.

The purpose of this prospective trial was to determine the changes in position and size of the mandible in children treated with either the Fränkel function regulator or Harvold activator. Forty-two 10- to 13-year-old children with Class II, Division 1 malocclusions were matched in triads according to age and sex and randomly assigned to either control, Fränkel function regulator, or Harvold activator groups. There were no statistically significant differences between the groups at the beginning of the study. After 18 months, significant increases in gonial angle and articulare-pogonion length in the Harvold group were attributed to a change in the location of articulare because the condyles were positioned downward and forward at the end of treatment. The main effects of both appliances were to allow vertical development of the mandibular molars and increase the height of the face. The Harvold appliance also proclined the lower incisors and increased mandibular arch length. We could find no evidence to support the view that either appliance was capable of altering the size of the mandible.