A “Forced Symmetry”: surgical planning protocol for the treatment of posterior facial asymmetries

Abstract

Dentofacial deformities are usually treated surgically and virtual hard tissue simulation has been advised for increasing the accuracy of hard tissue repositioning. However, asymmetric patients in addition to different lateral projections of hard tissues (i.e. gonial angles or parasymphyseal areas) may also exhibit a noticeable difference in surrounding soft tissue thickness that may be underdiagnosed. Consequently, symmetrical positioning of the hard tissue framework will not guarantee postoperative soft tissue symmetry. In this paper we introduce a new surgical planning protocol called “forced symmetry” that allows us to predict final soft tissue symmetry by mimicking facial symmetry using clinical rotation of the mandible in unoperated patients. Double cone-beam CT scanning allows surface-based superimposition of virtual head models in centric relation and in forced relation. The resultant composite head model reveals the target lateral projection of proximal fragments that guarantees the best soft tissue symmetry in the gonial areas.