Lip position analysis of young women with different skeletal patterns during posed smiling using 3-dimensional stereophotogrammetry. H Li, T Cao, H Zhou, Y Hou.

Date: January 2019.
Source: American Journal of Orthodontics and Dentofacial Orthopedics, Volume 155, Issue 1, Pages 64-70.
Highlights:
• Posed smile, lip position, and skeletal patterns were investigated in young women.
• Significant differences were found in interlabial gap and in the vertical, average, and horizontal groups.
• Intercommissural width did not differ significantly among groups.
• In the vertical group, the upper lip was elevated more in the vertical direction.
• The lower lip landmark showed no differences in any direction.
Introduction: The aim of this study was to explore the internal relationship between posed smile characteristics, lip position, and skeletal patterns in young women.
Methods: Fifty women between the ages of 20 and 30 years were enrolled and divided into 3 groups—vertical, average, and horizontal patterns— using the following parameters: FMA, GoGn-SN, and Jarabak ratio. Each subject was 3dMD scanned in natural head position and with a posed smile. The interlabial gap, intercommissural width, and smile index were calculated. The frontal region was selected as the reference plane for superimpositions. The changes of the lip landmarks in the vertical, sagittal, and coronal directions were investigated.
Results: The smile indexes were listed in the following sequence: vertical < average < horizontal. Significant differences were found in the interlabial gap among the 3 groups. Compared with the average and horizontal groups, the upper lip landmarks of the vertical group showed differences and changed more only in the vertical direction. However, the lower lip landmark showed no differences in any direction.
Conclusions: Different skeletal patterns have characteristic smile features. The vertical skeletal pattern affects upper lip movements because there is more space for upper-lip elevation. However, the vertical skeletal pattern has no effect on lower lip movement.

Article: Lip position analysis of young women with different skeletal patterns during posed smiling using 3-dimensional stereophotogrammetry.
Authors: Haizhen Li, Tian Cao, Hong Zhou, Yuxia Hou, College of Stomatology, Xi’an Jiaotong University, Xi’an, Shaanxi, China.