Assessment of the reproducibility of facial expressions with 3-D stereophotogrammetry

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There is little research into analyzing whether facial expression changes are secondary to actual treatment or normal day-to-day variation. This study aims to ascertain whether nine-facial expressions were reproducible. Thirty-nine white subjects performed nine-facial expressions, captured by three-dimensional stereophotogrammetry in three sessions. After initial capture (session 1), each expression was repeated after 15 minutes (session 2) and then 4 weeks (session 3) after the initial session. Statistical analysis was performed on the mean variability of facial landmarks between session 1 and 2 and session 1 and 3. Repose was the most reproducible expression. The least reproducible was "blow-out-the-cheeks." Analysis between session 1 and 2 showed no significant differences in expression reproducibility. Analysis between session 1 and 3 showed significant differences for the "smile-with-lips-open" and "blow-out-the-cheeks" expressions. Facial expressions are reproducible in a 15-minute period. There are significant differences in the ability to reproduce facial expressions 4 weeks apart for "smile-with-lips-open" and "blow-out-the-cheeks."