Reproducibility of the lip position at rest: A 3-dimensional perspective.

Abstract

In this study, we evaluated the reproducibility of the lip position at rest in 3 dimensions using reverse engineering software and stereophotogrammetric images. We used 3dMD Flex (3dMD, Atlanta, Ga) to obtain 60 stereophotogrammetric images from the same participant. Thirty images were obtained in 3 sessions on the same day, and the procedure was repeated 6weeks later for 30 more images. The surface-base registration, the segmentation of the upper and lower lips, and the 3-dimensional deviation analysis were performed with Geomagic Control (3D Systems, Rock Hill, SC) software. The Shapiro-Wilk test, paired sample t test, Bland-Altman plots, and Wilcoxon signed rank test were used for statistical analysis at a significance level of P<0.05. The deviations of the upper lip on the first images were between 0.16 and 1.39mm. The mean total deviation was 0.25±0.12mm. The mean deviation of the lower lip was 0.34±0.17mm. The deviations were observed between -1.96 and 1.97mm. When the mean positive (P=0.633 and P=0.171, respectively) and the mean negative (P=0.771 and P=0.842, respectively) deviations of the upper and lower lips were analyzed, there was no significant difference between the 2 time points. The results suggest that the rest position can be reproduced within a small range both on the same day and between the sessions. More research with larger samples is needed to confirm these results.