A cephalometric study of mandibular changes in modified function regulator (Fränkel) treatment.

A cephalometric study is reported of changes in mandibular dimensions occurring in treatment with a modified function regulator derived from the Fränkel (FR1) appliance; the findings are compared with those observed in a similar group of untreated control children. Both groups consisted of 16 boys and 13 girls with Angle Class II, Division 1 malocclusions. The mean age and age range of the groups were similar (114 months and 98 to 132 months, respectively), and the mean period of observation or treatment was 3 years (range 20 to 65 months in control children, 20 to 72 months in those receiving treatment). Statistically highly significant differences (P less than 0.005) were found in the treatment group for dimensions articulare-B point and articulare-1, gonion-B point and gonion-1, occlusal plane length, and posterior border-mandibular incisor distance. Smaller statistically significant differences were observed for the dimension articulare-pogonion, and between the Bolton plane and inferior border of the mandible. The changes appear to affect the relative distances between the anterior structures of the mandible, and articulare and gonion, respectively. The increases observed were between 2 and 3 mm (2.66% to 4.65%); although these values are small in relation to the overall dimensions of the variables investigated, they may significantly affect the clinical result. The most stable dimensions were found to be the posterior border of the mandible, width of the ascending ramus, and the oblique cross section of the mandibular body; these changes varied between 0.19 and 0.43 mm (0.62% to 1.5%).