2D and 3D analysis methods of facial asymmetry in comparison.

Symmetry is a significant factor, among others, influencing the attractiveness of human faces. Hence its restoration is an essential task in oral and maxillofacial surgery. Until recently, most of the techniques to objectively quantify the facial asymmetry were based on the evaluation of two-dimensional data, i.e. photographs. These techniques are well-established in literature and have in common that several landmarks in the face are identified manually and put together in a formula to obtain a facial asymmetry value. The increasing availability of three-dimensional measuring systems offers the possibility to perform an automated 3D analysis of the facial symmetry based on a dense 3D point cloud of the facial surface. The results of this analysis are on the one hand a mirror plane, which meets best the partial symmetry of the face regarding the median sagittal plane, and on the other hand a 3D asymmetry index quantifying the overall facial asymmetry characteristics. In this paper three selected 2D analysis methods and one 3D analysis method are compared.