Characterization of facial asymmetry in skeletal Class III malocclusion and its implications for treatment.

Jaw deviation is frequently seen in Class III patients. The aim of the study was to investigate asymmetric features of skeletal, dental and soft tissues in three types of jaw asymmetry based on our previously reported classification system. The cone-beam computed tomography (CBCT) images of 70 Class III patients were analysed. Group 1 patients showed large shift of menton and synchronous but smaller ramus deviation. The maxillomandibular complex had roll and yaw rotations to the menton-deviation side. Maxillary and dental asymmetry was obvious in transverse and vertical dimensions. Cant of occlusal plane and lip line was apparent. Group 2 patients also exhibited menton and ramus deviation to the same side but the discrepancy in ramus width was larger than menton shift. Asymmetry in Group 2 resulted from a bodily side shift of the maxillomandibular complex without obvious rotation. Group 3 patients had menton and ramus deviated in opposite directions which seemed secondary to a yaw rotation. Double-jaw surgery is generally required for Groups 1 and 3 while Group 2 patients may be successfully treated by mandibular surgery only provided that arch width discrepancy can be managed by orthodontic measures.