Treatment strategies for patients with hyperdivergent Class II Division 1 malocclusion: is vertical dimension affected?

INTRODUCTION: The dilemma of extraction vs nonextraction treatment, along with the uncertain potential of orthodontic treatment to control vertical dimensions, still remains among the most controversial issues in orthodontics. The aim of this study was to evaluate 2 contradictory treatment protocols for hyperdivergent Class II Division 1 malocclusion regarding their effectiveness in controlling vertical dimensions.

METHODS: The subjects were retrospectively selected from 2 orthodontic offices that used contrasting treatment protocols. The patients had similar hyperdivergent skeletal patterns, malocclusion patterns, skeletal ages, and sexes. Group A (29 patients) was treated with 4 first premolar extractions and "intrusive" mechanics (eg, high-pull headgear), whereas group B (28 patients) was treated nonextraction with no regard to vertical control (eg, cervical headgear, Class II elastics). Twenty-seven landmarks were digitized on lateral cephalometric radiographs before and after treatment, and 14 measurements were assessed. Geometric morphometric methods were also implemented to evaluate size and shape differences.

RESULTS: As expected, the maxillary and mandibular molars translated mesially and the mandibular incisors uprighted in group A but remained approximately unchanged in group B. The vertical positions of the molars and the incisors were similar between groups before and after treatment, although they were altered by treatment or growth. No significant differences were observed in the posttreatment skeletal measurements between the 2 groups, including vertical variables, which remained unaltered. Permutation tests on Procrustes distances between skeletal shapes confirmed these results.

CONCLUSIONS: This study demonstrated the limitations of conventional orthodontics to significantly alter skeletal vertical dimensions. More important factors are probably responsible for the development and establishment of the vertical skeletal pattern, such as neuromuscular balance and function.