There is a significant difference in the perception of smile aesthetics with varying amounts of gingival show. There is a clear threshold of acceptance up to 3 mm of gingival display for the female videos and 1.5 mm in for the male videos, after which the aesthetics of the smile decline with increments of increasing gingival display. No significant differences were observed in the perception of smile aesthetics with varying amounts of gingival show between orthodontists, dentists and lay people.
Zhang et al. (Wed,) studied this question.