Permanence of skeletal changes after function regulator (FR-2) treatment of patients with retrusive Class II malocclusions.

The purpose of this study was to examine the skeletal changes produced by the Fränkel function regulator (FR-2) appliance during the treatment of patients with mandibular retrusive Class II malocclusions and to characterize the permanence of these changes in the years after treatment (5 years, on average). Data from the pretreatment, posttreatment, and long-term serial cephalograms of 14 patients who received FR-2 treatment were compared with data obtained from untreated controls and from published standards. Relative to controls, FR-2 therapy produced a statistically significant decrease in the ANB angle and an increase in the rate of mandibular growth. At the same time, no maxillary effect was noted. During the post-FR-2 period, the rate of mandibular growth showed no compensatory decline or "rebound." Instead, it was remarkably similar to that inferred from age-matched and sex-matched normative standards. The present study thus supports the conclusion that FR-2 therapy, in conjunction with a period of postfunctional fixed- or removable-appliance therapy designed to perfect the occlusion, can produce a statistically and perhaps clinically significant relative increase in mandibular length.