Prediction of soft tissue profile changes following orthodontic retraction of incisors in Iranian girls.

Objective: To study the relationship between incisor retraction and soft tissue profile alterations and to identify and quantify the parameters that influence it.

Methods: Pre- and posttreatment lateral cephalograms of 37 Class I and Class II Division 1 Iranian females in whom at least one maxillary premolar was bilaterally extracted were analyzed and compared.

Results: Significant positive correlations were found between retraction of the maxillary and mandibular incisors and posterior movement of the upper lip (r=0.53, P<.001), the lower lip (r=0.63, P<.001), thickness increase of the upper (r=0.59, P<.001) and lower (r=0.69, P<.001) lip, increase of the soft tissue lower anterior face height (r=0.81, P<.001) and lower soft tissue component (r=0.49, P<.001), and an increase of the nasolabial angle (r=0.43, P<.01). The ratio of maxillary incisor to upper lip retraction was 2:1.

Conclusions: In Iranian girls, a strong correlation exists between anterior tooth retraction and the position and configuration of both lips.