Lip morphological changes in orthodontic treatment. Class II division 1: malocclusion and normal occlusion at rest...

To evaluate the morphological changes in the lips and to determine the degree of improvement in the smile after orthodontic treatment for Class II division 1 malocclusion.

The sample subjects were divided into two groups: a group that consisted of 20 adult female patients with Angle Class II division 1 malocclusion and a control group that consisted of 28 adult female volunteers with normal occlusion. Frontal photographs were taken before and after orthodontic treatment, and 35 landmarks were placed on each tracing made from the photograph. Thereafter, landmarks were digitized into an x- and y-coordinate system with the subnasal point as the origin. The comparisons between pretreatment and posttreatment at rest and on smiling, and the comparisons between Class II division 1 and control group were made using Student's t-test.

Both the upper and lower lips in the smile of patients in the Class II division 1 pretreatment group were positioned downward, and the upward movement of the upper lip and mouth corners was smaller in comparison with the control group. These characteristics of the Class II smile improved after orthodontic treatment, but the differences with the control group remained unchanged immediately after treatment.

The soft tissue morphology shows a relative improvement after orthodontic treatment.