Objective: To quantify and compare ideal and acceptable ranges of five smile characteristics and investigate differences in attractiveness ratings between Canadian orthodontists and laypersons.
Methods: Gender neutral circum-oral photographs were adjusted from an ideal dental and lip configuration during a posed smile. Symmetric dental configurations were manipulated using Adobe® Photoshop® 7 to alter Smile Arc (SA), Buccal Corridor (BC), Overbite (OB), Central to Lateral Incisal Discrepancy (CLID), and Gingival Display (GD). 47 orthodontists and 103 laypersons, were surveyed. Multiple Mann Whitney-Wilcoxon tests with Bonferroni-Holm correction (p<0.0025) was used to define ideal and maximum acceptable ranges.
Results: Orthodontists were more sensitive in detecting deviations from ideal and acceptability thresholds for SA by 1mm (p<0.05); and BC by 4.1mm (p<0.0025). Ideal esthetic values were clinically noticeable and significantly different; orthodontists preferred 1.5mm deeper OB (p<0.0025) and 2.2mm more GD (p<0.0025). Both samples found BC was clinically acceptable (>67%) of the time, while SA was not clinically acceptable <67%. The limits of acceptability for SA were scored less than 50% by 57% orthodontists; whereas it was scored 59% by 44% of laypersons.
Conclusions: Highly significant differences in preferences of the smile characteristics were found. Laypersons were less discriminating and had wider ranges of acceptability than orthodontists. Both groups were more critical of SA vs. BC revealing that SA had an overwhelming clinical impact on smile esthetics. Although BC attractiveness may decrease at the limits of acceptability, the perceived deviation from ideal still falls within an acceptable range to a majority of people.