Layperson's perception of axial midline angulation in asymmetric faces

Asymmetric facial features such as a deviated nose and chin are common and known to affect smile esthetics. When presented with these asymmetries, the clinician must consider the impact they will have on the smile design parameters-especially the placement and angulation of the dental midline, which is a common starting point for a case involving smile design. The purpose of this article is to determine if the nose and chin deviations affect the perception of dental midline angulation.

An asymmetric facial model (AFM) was created from a digital symmetric facial model, used in a previous study by digitally deviating the nose and chin to the same side. Eight different pictures of this AFM were created, each with different degrees of maxillary midline angulation (both in and against the direction of the deviated nose and chin). Using a visual Likert scaled delivered via Websurvey in the private practice setting, one hundred and ninety-six randomly selected laypersons were asked to evaluate each image according to their own notions of beauty.

A minor axial dental midline angulation of 3.5° can be perceived independently of the direction of the cant. All pictures where the midline was canted pointing in the opposite direction of nose and chin deviations presented lower rating mean values.

Off-center noses and chins can influence the perceived attractiveness of a smile with a canted dental midline. The degree and direction of a canted midline can influence the harmony between the smile and overall face, with canting in the same direction of the asymmetric features being rated as more attractive.

The dental midline should be as vertically straight as possible. If a midline cant is present, however, it is more favorable to have a dental midline angulation which points in the same direction as nose and chin deviations, rather than in the opposite direction.