Purpose: To collect facial stereo images of different lip protrusion by using three dimensional surface imaging device, and investigate facial aesthetic evaluation and differences between orthodontists, general dentists and laypeople.
Methods: In this study, one college student was recruited to take a three-dimensional image of the natural head and face. The software was simulated with a gradient of 2 mm to make the soft tissue lips move back and forth along the sagittal axis from the VSL line.The movement limit was 6 mm in front of and behind the VSL line. The observers included orthodontists, general dentists and laypeople. The data were analyzed with SAS 9.4 software package,visual analog scoring (VAS) was used for evaluation, and fixed-effect model was used for statistical analysis.
Results: The results showed that when the lip was on the VSL line, it got the highest scores amount all three groups and had no significant difference.When the lip became protrusive or retractive, it had negative impact on facial esthetics. There were significant differences in the scores of three groups in every 2mm of lip protrusion and lip retraction(P＜0.05). VAS 5 points or less were used as the unacceptable facial aesthetic score. The results showed that lip protrusion was 4 mm before the VSL line in the orthodontist group and less than 5 in the laypeople group . When the lip protruded 6mm before the VSL line and retracted 4 mm behind the VSL line, the scores of the three groups were lower than 5 points. The results also showed that male evaluation of lip protrusion 2 mm before the VSL line had a lower score than female; On the other hand, female evaluation of lip retraction behind the VSL line above 4mm had a lower score than male.
Conclusions: Lip position has significant effect on facial aesthetics. Different observers had significant differences in the evaluation of lip position on facial aesthetics. It is suggested that orthodontists need more communication with patients in determining the target position of orthodontic treatment to improve treatment satisfaction.