Perception of discrepancy in the upper midline position in conjunction with the gingival display according to various occupations in Iran

OBJECTIVE: This study evaluated the influence of various gingival displays on the esthetic perception in the presence of upper dental midline discrepancy. METHODS: A smiling image of a male subject was altered digitally to produce five image series normal smile (series A), decreased tooth show (series B), increased gingival show (series C), maxillary cant (series D), and asymmetric upper lip elevation (series E). In each image series, the midline was deviated to the right and left incrementally. A total of 210 raters (four professional groups and laypersons, n = 42 in each group) determined the midline deviation threshold and the attractiveness of midline position in each series. RESULTS: The right and left thresholds were statistically similar for the symmetrical series (A, B, and C), while for series D, the right threshold was significantly lower. In most rater groups, the mean threshold order was B > A > E > C > D. In all the series, the raters selected the coincident midline as the most attractive series except for series D, for which 1–2-mm deviations to the left were selected as the most attractive by almost all the groups. CONCLUSIONS: It is crucial to establish the coincident midline position in a symmetrical smile, especially when a gummy smile exists. In the asymmetrical gingival show, a coincident midline might not be the most esthetic midline position.