Three-dimensional (3D) dynamic changes in nasolabial symmetry following Le Fort I maxillary advancement in Class III patients

The use of 3D facial motion capture systems has enabled the analysis of nasolabial soft tissue symmetry following a Le Fort I advancement osteotomy. Twenty-two Class III patients underwent facial motion capture (Di4D Pro), from rest to maximum lips apart smile, immediately prior to and a minimum of four months post-surgery. The pre- and post-surgical 3D facial motion sequences were aligned on the forehead. Sixteen nasolabial landmarks were digitised on the rest image and automatically tracked through the remaining 3D sequence. The x, y, and z-coordinates of these landmarks at rest, mid-smile, and maximum smile were extracted. The asymmetry score was calculated as the mean difference in Euclidean distance between original and mirrored landmark pairs. After a Le Fort I advancement, the nasolabial region was more asymmetric at the mid-point and at maximum smile, but not at rest. Using static images at rest to assess nasolabial region asymmetry may not be clinically valid as differences in asymmetry appear only as individuals begin and complete a maximum smile.