Relationship between lip-closing force and three-dimensional lip morphology in adults with straight facial profile

The purpose of the present study was to investigate the relationship between multidirectional lip­closing force and the three-dimensional morphology of perioral soft tissue in adults. Twenty-three Japanese adults with straight facial profiles participated in this study. The signals of directional lip­closing force (DLCF) were investigated in 8 directions. Three-dimensional morphology of perioral soft tissue was recorded using a 30 surface-imaging device. Correlations between lip-closing force and the three-dimensional morphology of the perioral soft tissue were analyzed statistically. Upper lip-closing force significantly correlated with the anteroposterior, vertical, transverse morphology of the upper lip, while lower lip-closing force did not correlate with the anteroposterior, vertical, or transverse morphology of the lower lip. In adults with straight facial profiles, associations were found between upper lip-closing force and upper lip morphology. There were no associations between lower lip-closing force and lower lip morphology.