Facial movement in 3 dimensions: average templates of lip movement in adults.

Abstract

To construct 3-dimensional (3D) templates of average lip movement based on a group of normal healthy subjects. Cross-sectional study. School of Dentistry, Cardiff University, United Kingdom. One hundred fifteen white subjects were asked to perform 2 reproducible verbal gestures (/puppy/ and /rope/) in a normal relaxed manner. The sequences were captured using a noninvasive, 3D motion scanner (3dMDFace Dynamic System). Mesh-registration software was used to align sequential facial shells to a standardized reference plane. Lip movement during the verbal facial gestures was quantified using the displacement vectors (x, y, z coordinates) of 6 lip landmarks of sequential 3D facial shells subtracted from the reference or rest shell. Descriptive statistics were used to build references for average lip movement, and independent t tests were used to compare lip movement between men and women. Mean reference movements were created for lip opening, lip stretch, and lip purse that corresponded to the visemes /pu/ /ppy/ and /rope/, respectively. There were statistically significant differences in the lip movement between genders for the visemes /pu/ and /ppy/, although when quantified these were found not to be of clinical significance. Men favored left-sided movement and women right-sided movement, although only slightly--again, when quantified, this was considered to be within symmetrical limits. It was possible to quantify and create normal templates of lip movement for the words /puppy/ and /rope/. Men and women show similar standardized lip movements for these 2 words.