Influence of gingival display on smile aesthetics in Japanese.

The aim of this study was to evaluate the influence of the amount of gingival display on smile aesthetics as assessed by Japanese orthodontists and dental students. A coloured photograph of a smiling female, displaying the first molar to first molar, whose upper lip was tangent to the upper gingival margin of the upper central incisors (zero point), was constructed from different subjects. Gingival displays were modified by moving the teeth within the lip frame in 1 mm increments, from -5 to 5. Using a visual analogue scale (VAS), 31 Japanese orthodontists and 55 Japanese dental students rated the attractiveness of the 11 smiles with altered gingival display. There was no significant difference when judging the effects of the gingival display on the smile attractiveness between the male and the female raters for both the orthodontists and dental students. Kruskal-Wallis tests revealed significant differences in the median aesthetic scores for both the orthodontists and dental students. For the orthodontists, the median aesthetic score increased gradually from -5 to 0 mm and then decreased from 0 to 5 mm. In particular, it decreased to become clinically significant (15 per cent VAS difference) from 0 to 3 mm. For the dental students, the median aesthetic score increased gradually from -5 to -2 mm and then decreased from -2 to 5 mm. The dental students were less tolerant of a more 'gummy' smile than the orthodontists.