Interceptive treatment of Class II malocclusion: What are the morphological characteristics of therapeutic success?

Cooperation and choice of device are not sufficient to predict the success of interceptive treatment in Class II, 1. The aim of this study was to identify specific factors of patient morphology that predict success.

A retrospective, prognostic, comparative, monocentric, intention-to-treat study was carried out. The criterion for therapeutic success was normalization of the ANB. The success and failure groups were statistically compared with an alpha risk of 5%.

95 patients who underwent interceptive treatment close to their growth peak were included. The probability of successful treatment was a decreasing function of FMA, SNA, ANB and IMPA and an increasing function of SNB, ramus height and mandibular length. The proposed logistic equation offers a sensitivity of 82% and a specificity of 87%.

Hyperdivergence below surgical values is not a factor in mandibular response failure. Hypodivergence is a factor in success. A stocky mandible (large ascending ramus, large horizontal ramus) responds well. Rather than ramus height, mandibular length is decisive: the greater the retromandibular height, the greater the chances of success. Pre-existing mandibular incisor vestibuloversion is a factor in failure.

The accumulation of negative predictive factors may point towards an alternative therapeutic solution or prompt the patient and family to be informed of the difficulties inherent in the treatment.