A comparison of skeletal and dental changes produced by function regulators (FR-2 and FR-3).

The lateral skull radiographs of subjects taken before and after treatment with the FR-2 (N = 99) and FR-3 (N = 30) of Fränkel were compared to contrast the effects of each appliance. The major skeletal effect of both appliances was on the mandible, the FR-2 group showing a significantly greater annual increase in total length and ramus height (P less than 0.001) and the FR-3 group a significant change in position downward and backward facilitated by an opening of the cranial base angle. The greater annual increase in lower facial height, compared with a control group, seen in both FR groups was accompanied by a reduction in overbite, which was greater in the FR-2 group. The favourable change in overjet seen in both FR groups was contributed to by alteration in upper and lower incisor inclination.