Mandibular incisor position changes in relation to amount of bite jumping during Herbst/multibracket appliance treatment: a radiographic-cephalometric study.

INTRODUCTION: The aim of this study was to analyze the effect of the cast Herbst/multibracket (MB) appliance on the position of the mandibular incisors in relation to the amount of mandibular advancement at the beginning of treatment.

METHODS: We screened 133 patients with Class II Division 1 malocclusions. The subjects were divided into 3 bite-jumping groups: I, 49 subjects with bite jumping of <7 mm; II, 44 subjects with bite jumping of 7.5 to 9.5 mm; and III, 40 subjects with bite jumping of >9.5 mm. Only group I with small (S) and group III with large (L) bite jumping were considered. The average ages of the subjects in the 2 bite-jumping groups were 13.6 +/- 2.4 years in the S group and 14.7 +/- 4.7 years in the L group. The average treatment time with the Herbst/MB appliance was 19 months. Lateral headfilms were evaluated at 3 times: before Herbst treatment, after Herbst treatment, and after MB treatment.

RESULTS: During the Herbst phase, the mandibular incisors were significantly intruded, protruded, and proclined in both bite-jumping groups. Larger tooth movements occurred in group L than in group S. During the MB phase, comparable relapsing incisor tooth movements were seen in the 2 bite-jumping groups. There was moderate correlation between bite-jumping and incisor position changes during the Herbst and the Herbst/MB treatment periods. No associations were found between the amount of bite jumping and the changes of sagittal and vertical jaw relationships, age, and treatment growth period.

CONCLUSIONS: During the Herbst treatment period, there was an association between bite jumping and movement of the mandibular incisors: the greater the bite jumping, the larger the intrusion, protrusion, and proclination of teeth. During the MB treatment period, relapsing incisor tooth movements occurred that were independent of the original amount of bite jumping.