Evaluation of Bionator Therapy in Treatment of Class II Malocclusions

Two-phase orthodontic treatment of Class II malocclusions is a debated topic, primarily because the benefits of early intervention have not been consistently reproduced among researchers. Objective: The present study compared the cephalometric results of matched samples of (1) Bionator treatment plus Edgewise treatment against (2) later treatment with the Edgewise appliance alone. Methods: 50 consecutively treated American white youths received phase 1 treatment with a Bionator and later treatment with full appliances. The comparison group (n = 50) consisted of subjects treated in a single phase with Edgewise appliances only. Importantly, subjects in the two samples were matched, on a one-to-one basis, for demographic and cephalometric variables (ANB, SNA, SNB, NAP, FMA) to ensure comparability in the nature and severity of the malocclusions. Results: Neither of two integumental variables (Z angle, E plane) differed statistically, but key skeletal variables did differ, namely ANB and NAP. The two-phase group was discernibly more orthognathic at the end of treatment, with most of the correction coming from mandibular growth rather than maxillary restriction. None of the dental variables differed statistically except the position of the maxillary incisors which were slightly more proclined in the two-phase group, and this was due to operator preference. The two-phase subjects had a lower rate of premolar extraction (12% vs 84%). Conclusion: Overall, the two-phase group achieved a better bony facial profile, with the majority of the skeletal and dental correction occurring during the Bionator phase of treatment. These favorable results contrast with published randomized clinical trials (RCTs), possibly because of differences in patient selection, appliance design, or failure of RCTs to differentially diagnose which cases would benefit from two-phase treatment.