The influence of varying degrees of maxillary gingival display on perception of smile aesthetics: A dynamic smile visualisation study

Objective: To assess the influence of varying degrees of gingival display on perception of smile aesthetics judged by orthodontists, dentists and lay people. Design: Cross-sectional study. Setting: Barts and the London, School of Medicine and Dentistry, Queen Mary University of London, UK. Participants: Three groups of raters comprising 25 orthodontists, 25 dentists and 25 lay people. Methods: Videos in increments of 1.5 mm of the final lip position ranging from 3 mm incisal coverage to 7.5 mm of gingival display were produced. Three rater groups assessed the attractiveness of smile videos using a visual analogue scale (VAS). Multiple regression analysis was undertaken, and images were compared using the Tukey HSD method. Results: The intraclass correlation coefficient (ICC) was 0.65% (95% confidence interval 0.59–0.71), indicating moderate intra-rater reliability. The highest ranking for female videos was with 1.5 mm of incisal coverage, with no significant difference between 3 mm of incisal coverage and 3 mm of gingival exposure. For the male videos, the highest ranking was 0 mm of gingival show, with no significant difference between 1.5 mm of incisal coverage and 1.5 mm of gingival exposure. There was a significant drop in the scores with further increase in gingival exposure, with more than 6 mm being rated very low aesthetically. Video rating was not influenced by rater group (female: P = 0.60; male: P = 0.06), rater gender (female: P = 0.17, male: P = 0.74) or rater age (female: P = 0.16, male: P = 0.25). Conclusion: 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.