Soft-tissue changes associated with maxillary incisor retraction.

The nature of incisor retraction and lip adaptation is still controversial. The present study was undertaken to determine the response of upper and lower lips to maxillary and mandibular incisor movement. Cephalometric head films of thirty late-adolescent and early-adult female patients were analyzed for changes in the integumental profile with treatment. Sample selection was intended to reduce variables caused by growth and sex differences. A stepwise multiple regression analysis (forward) revealed a complex interaction between dentition, bony structures, and soft tissues of the perioral area. The lower lip was more variable than the upper lip to differences in the upper incisor movement. The upperlip at labrale superius was found to be more variable with increased retraction of the upper incisors. In the prediction equation, change of sulcus superius had a more direct relationship with retraction of labrale superius and labrale inferius than with dental movement. Pogonion and/or menton entered at statistically significant levels into four (LS, LI, SI, Stm I) of the six prediction equations, indicating that mandibular position is of paramount importance in the prediction of vertical and/or horizontal changes in the upper and lower lips. The upper lip response was related to both upper and lower incisor movement, mandibular rotation, and the lower lip. Upper incisor point position related a moderately high correlation for the prediction equation for change in labrale superius. Lower incisor movement did not correlate with change of either the upper or lower lip. The equations derived were an improvement over previous prediction methods.