The aim of this study was to determine the esthetic perception of some components of the smile such as gingival exposure, level of the gingival margins, length of the crowns, maxillary midline and inter-incisor diastema by laypersons, dental students and dental professionals.

Six hundred and thirty-four Portuguese people (292 laypersons, 241 dental students and 101 practitioners) assessed the esthetics of 13 altered pictures of the same smile arranged at random. The manipulated components (gingival exposure, level of the gingival margins, length of the crowns, maxillary midline and inter-incisor diastema) were altered using Adobe Photoshop^® CS6 software. The classification of the pictures was done using the visual analogue scale (VAS), scored 1 to 10. The responses were then analyzed and processed with SPSS^® version 21.0 using tests of average equality and correlation.

The medium smile was the most appreciated smile, whereas the high smile and diastemas were considered to be the least esthetic. Among all the modified parameters, the midline shift was the least perceptible. The preference for asymmetry of the gingival margin at the maxillary lateral incisors (MLI) and the symmetry in the length of the crowns of the maxillary central incisors (MCI) reflected the importance given to MCI during smiling. Gender did not influence the scores given, except for gummy smiles, while younger people gave the highest scores. Regarding academic/professional training, there was an intra-group homogeneity of opinions as laypersons tended to give higher scores and professionals tended to give lower scores, but with no correlation between the variables. The fact that the laypersons had received orthodontic treatment, or not, had no influence on their perception.

Laypersons, dental students and dental professionals had different perceptions of attractiveness when evaluating different modified features, except for diastemas, but with no significant differences between them. Gender was correlated with a very high smile. Age did not correlate with the judgment of the evaluators. There was no difference between the perceptions of laypersons, whether they had received orthodontic treatment or not.