CBCT Assessment of Three-Dimensional Changes of the Upper Lip after Le Fort I Maxillary Advancement

Hypothesis: This study investigates how the upper lip responds in three dimensions to Le Fort I maxillary osteotomy with advancement. It was hypothesized that there are no significant changes in the upper lip position, length, thickness and volume before and after Le Fort I maxillary osteotomy with advancement as measured at various anatomical locations. Objective: To determine the following measurements before and after Le Fort I maxillary osteotomy with advancement: (1) upper lip volume, (2) upper lip thickness changes at Subnasale, soft tissue A point, Labiales Superior, Christa Philtri, and commisures of the lip, and (3) upper lip length changes at the same points defined above. The above measurements were compared to subsequent osseous changes. Method: Computed tomography scans of sixteen subjects before and after Le Fort I osteotomy were compared retrospectively. Volumetric measurements were obtained by segmenting the upper lip at designated anatomical locations. The linear measurements of lip length and thickness were also assessed at predetermined locations. The resulting soft tissue measurements were then compared to determine where the changes ocurred. Statistical analyses were performed and the relationships between osseous movements and soft tissue responses were determined. Results: On the average, the maxilla was advanced 5.49mm after Le Fort I osteotomy. The mean value of downward movement was 1.74mm at Ortiz-Giuliani point. No statistically significant differences were found for upper lip volumetric values. Lip thicknesses were statistically significantly smaller after surgery, except at lip commisures. The upper lip length was increased and the upper lip vermillion border was widened after surgery. Conclusion: The ratio of skeletal changes due to surgical movement doesn’t correspond to soft tissue movement in a 1:1 ratio. Overall upper lip thinning and lengthening effect was shown after surgery. More research is needed to further elucidate soft tissue responses to surgical skeletal movement.