Predictability of upper lip soft tissue changes with maxillary advancement.

To improve predictability of the esthetic (soft tissue) results after maxillary advancement surgery, a better understanding of the relationships between the dental osseous movement and overlying soft tissue response is essential. Twenty-one adult patients who underwent isolated maxillary advancement via LeFort I osteotomies without adjunctive nasal soft tissue procedures and/or V-Y closure of the vestibular incision were studied. Homogeneity of the patient population was ensured by selecting cases with less than 2 mm vertical change. The mean maxillary advancement and mean change in Sn was calculated for these 21 patients. Additionally, the 21 patients were subdivided into two groups based on lip thickness: group 1 (lips between 10 and 17 mm thick) and group 2 (greater than 17 mm thick). In each patient group a linear regression (LR) was determined on the magnitude of maxillary advancement (MMA) to the change in soft tissue subnasale (Sn) and on the ratio of Sn change to bone move. The results using mean data showed that the relationships produce significantly high standard deviations; thus, a general correlation between change in soft tissue position to bony advancement cannot be made. Individuals with thin lips (12 to 17 mm) had a good correlation between the magnitude of bony move and amount of soft tissue change. However, increased lip thickness (greater than 17 mm) produced a less predictable correlation between soft and hard tissue changes. All lips thinned around 2 mm when compared with preoperative values. Lip thickness stabilized at approximately 6 months postoperatively.