title: Reproducibility of the lip position at rest: A 3-dimensional perspective.
abstract: BACKGROUND
  In this study, we evaluated the reproducibility of the lip position at rest in 3 dimensions using reverse engineering software and stereophotogrammetric images.
  
  
  METHODS
  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 6 weeks 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.
  
  
  RESULTS
  The deviations of the upper lip on the first images were between 0.16 and 1.39 mm. The mean total deviation was 0.25 ± 0.12 mm. The mean deviation of the lower lip was 0.34 ± 0.17 mm. The deviations were observed between -1.96 and 1.97 mm. 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Research assistant, Department of Orthodontics, Dental Sciences Center, Gülhane Military Medical Academy, Etlik, Ankara, Turkey. Electronic address: furkandindaroglu@yahoo.com.tr.
authors.forename: Furkan
authors.initials: F
authors.lastname: Dindaroğlu
authors.affiliation: Postgraduate student, Department of Orthodontics, Dental Sciences Center, Gülhane Military Medical Academy, Etlik, Ankara, Turkey.
authors.forename: Gökhan Serhat
authors.initials: GS
authors.lastname: Duran
authors.affiliation: Associate professor, Department of Orthodontics, Dental Sciences Center, Gülhane Military Medical Academy, Etlik, Ankara, Turkey.
authors.forename: Serkan
authors.initials: S
authors.lastname: Görgülü
mesh_terms: D000328:Adult; D006801:Humans; D021621:Imaging, Three-Dimensional; D008046:Lip / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D008297:Male; D015203:Reproducibility of Results; D012146:Rest