Abstract: Objective: To study the effect of chin and lip positions on the facial attractiveness. Methods: A woman with a charming profile was selected and 35 3D head models with different chin and lip positions were obtained by Maya software. The orthodontists (professional group, n=50) and laypeople (nonprofessional group, n=103) were chosen to score the head models by visual analogue scale (VAS). Results: Using "E Line" as the reference, the protrusion was defined as a positive value and the backward was regarded as a negative value. Both groups considered that the chin and lip protrusions were most beautiful when they were 0mm (that is, they were tangent to the "E line"). Moreover, the lip projection of +6 mm, -6 mm and the chin protrusion of +4 mm were regarded as the most unattractive. The score of the non-professional group was significantly higher than that of the professional group when the lip protrusion was +6 mm, +4 mm, -6 mm, and chin protrusion was +4 mm. Conclusion: The professional group preferred a slightly concave lip position, while the non-professional group was more tolerant of a slightly convex lip position. Both groups regard a too protuberant chin shape as unpleasant. Orthodontists believe that it is aesthetically pleasing when the chin and lip protrusions changed in accordance with each other. When the protrusion of chin and lips moved within ±2 mm relative to the E line, the aesthetic effect was highly accepted by orthodontists and the general public.

Key words: orthodontics, chin positon, lip position, esthetic evaluation