Effect of nonextraction and extraction orthodontic treatments on smile esthetics for different malocclusions

Smile esthetics is a critical factor for evaluating orthodontic treatment outcomes. In this study, we evaluated the differences in esthetic perceptions and smile variables between extraction and nonextraction treatments for different malocclusions.

Ninety participants were divided into 3 groups according to their pretreatment overjet (group I, 0-4 mm; group II, >4 mm; group III, <0 mm), with 15 extraction participants and 15 nonextraction participants in each group. Posttreatment frontal smiling photographs were evaluated by 30 raters (10 orthodontists, 10 general dentists, 10 laypeople), and 9 smile variables were measured.

Smile perception for the group II extraction subjects was higher than for the nonextraction subjects by the orthodontists and general dentists. Regardless of the type of treatment, group III subjects were rated lower than those in groups I and II. The arch form index, maxillary incisor show, and smile arc were greater in the extraction participants. In multiple regression analysis, nonextraction and group III correlated negatively with the esthetic score. Maxillary incisor show, tooth number display, and buccal corridor ratio correlated positively with the esthetic score.

Group II extraction subjects were rated higher than the nonextraction subjects by dental professionals. A smile with greater maxillary incisor show, number of displayed teeth, and buccal corridor ratio was considered more esthetic.