Computer-based smile esthetic surveys based on emoticon (slider) technology allow control of variables and the possibility of obtaining continuous data. However, differences in the perception of smiles using different facial perspectives have not been resolved.
Objectives: To quantify the ideal values and the range of acceptability for specific smile variables judged by laypersons from a full face perspective for comparison to lower face data. Methods: Ninety-six laypersons judged each smile variable that was digitally embedded in mirrored and symmetric male or female full faces, which had previously been determined by peers to be of average attractiveness. Smile arc, buccal corridor fill, maxillary gingival display, maxillary midline to face, maxillary to mandibular midline discrepancy, overbite, central incisor gingival margin discrepancy, maxillary anterior gingival height discrepancy, incisal edge discrepancy and cant were manipulated by the raters using emoticon technology that allowed the variable to morph and appear continuous on a computer monitor. Medians for each smile variable were compiled and Fleiss-Cohen weighted kappa statistic was used to measure reliability. Multiple randomization tests with adjusted p-values were used to compare these data with those for lower face views.
Results: Reliability ranged from 0.25 for ideal overbite to 0.60 for upper midline to face, except in the case of the buccal corridor limits, which each had a KW near 0. There were no statistically significant differences between ratings for the male and female raters. The following variables showed statistically significant differences when compared with the lower face view: ideal smile arc, all 3 buccal corridor measures, gingival display up and down, U to L midline, minimum overbite, lateral gingiva up and down, maximum and ideal lateral step, and occlusal cant. In all but 5 cases (ideal smile arc, ideal buccal corridor, maximum gingival display, upper to lower midline and occlusal cant), these differences were not considered to be clinically meaningful due to the small magnitude of the differences (less than 1 mm) and therefore similar to the lower face perspective. While the smile arc numbers differed from those found with the lower face perspective due to a model with different lip curvature, the principle of tracking the curve of the lower lip was consistent for both perspectives. For the full face view, raters preferred less maximum gingival display than the lower face rater by several millimeters. Full face raters favored less buccal corridor than lower face raters, and allowed more upper to lower midline discrepancy. The full face raters allowed less cant of the occlusal plane than the lower face raters.
Conclusion: Reliability was fair to moderate with the exception of the buccal corridor limits. Most variables showed no clinically meaningful differences from the lower face view. The acceptable range is quite large for most variables. Detailed knowledge of the ideal values of the various variables is important and can be incorporated into orthodontic treatment to produce an optimal esthetic smile.