With interest, I read about the study by Williams et al in the February 2014 issue of the AJO-DO . I congratulate and appreciate the authors of this study for their efforts in bringing up the important issues regarding the perceptions of midline deviations among different facial types. I have 2 concerns about the study, focusing on the selection of the models who were photographed and the gender ratio of the evaluators.

As shown in Figures 2 and 3, the evaluators thought that the female model gained significantly more attractiveness than the male model over all 5 levels of deviations. The threshold of acceptance for the woman was also higher than that of the man. These results may be attributed to the difference of overall full-face attractiveness between the female and the male models. The evaluators might have been distracted by the models’ hairstyles, the black triangle space between the maxillary central incisors of the man, or other features not related to dental symmetry. The results of this research would be more persuasive if the male and female models selected as the experimental subjects had been determined by peers to be of average and equal attractiveness.

What’s more, the gender ratio of the evaluators was not taken into account. The effect of the evaluator’s gender on the perception of midline deviation has been controversial. One possible reason would be that the age range of the evaluators was not clearly specified in previous studies that claimed no differences in the perception of smile esthetics based on the evaluators’ gender. In this study, the evaluators’ ages were specified to be similar to those of the subjects. This was consistent with a previous study that concluded that the gender of the evaluator did affect the perception of midline deviation. It seemed that the effect of the evaluator’s gender on perceived smile esthetics would be more evident in a population of similar age. A balanced gender ratio might be essential in future studies.

Thanks again for presenting this contribution.