Effect of maxillary incisor labiolingual inclination and anteroposterior position on smiling profile esthetics

Abstract

Objective: To test the null hypothesis that there is no effect of maxillary incisor labiolingual inclination and anteroposterior (AP) position on smiling profile esthetics in young adult females.

Materials and methods: A facial smiling profile photograph of a Chinese woman with a normal profile, a Class I occlusion, and a Class I skeletal pattern was digitized. The digital image was modified to obtain four series comprising 29 smiling profiles. The sample of individuals rating these pictures comprised 21 orthodontic professionals and 66 undergraduates. Post hoc tests were done with the Student Newman Keuls method to analyze the data.

Results: Significant differences (P < .001) were detected when each photograph's ratings were compared. The smiling profile with the highest score was the one with 5° lingual inclination, while the ones with 15° labial inclination or 4-mm retrusion had lower scores than the others. Maxillary incisor protrusion and lingual inclination were preferable compared with retruded or flared incisors. There was no significant discrepancy between the professional and nonprofessional groups in terms of their assessments.

Conclusions: The hypothesis is rejected. Both maxillary incisor labiolingual inclination and AP position play an essential role in the esthetics of the smiling profile. However, when formulating treatment plans, dentists should never underestimate the labiolingual inclination's influence on the smiling profile.

Figure 1

(A) Natural profile. (B) Smiling profile. (C) Maxillary incisor FA on GALL.

Figure 2

(A) Maxillary incisors were inclined labially by 5°, 10°, and 15° and lingually by 5°, 10°, and 15°, respectively. (B) Maxillary incisors were moved anteriorly by 1 mm, 2 mm, 3 mm, and 4 mm and posteriorly by 1 mm, 2 mm, 3 mm, and 4 mm, respectively. (C) The maxillary incisor labiolingual inclination was altered with FA 2 mm anterior to GALL. The last image was gained through labiolingual inclination alteration with FA on GALL. (D) The maxillary incisor labiolingual inclination was altered with FA 2 mm posterior to GALL. The last image was gained through labiolingual inclination alteration with FA on GALL.

Figure 3

Interaction bar plot for raw data.

Figure 4

The line is GALL, as described by Andrews and Andrews. (A) Relatively attractive group, group 5; (B) acceptable group, group 4; (C) unattractive group, group 1; and (D) relatively unattractive group, group 2.