Investigating the Accuracy and Reproducibility of 3dMD Imaging System

Objectives: This study aims to evaluate the accuracy of 3dMD imaging and find standard facial expressions that can be best reproduced by 3dMD imaging for soft tissue analysis.
Methods: Three-dimensional (3D) ST facial landmarks were obtained from 40 adults not undergoing orthodontic treatment through the use of 3dMD facial photographic software. A total of 16 landmarks were used and 19 parameters were measured for surface distances (6 in vertical, 8 in anterior posterior, and 5 in transverse). 3dMD images of four different facial expressions (repose (R), maximum intercuspation (MIP), posed smile (S), and smile with lips closed (SLC)) were taken at 0hr, 1hr, 24hr, 1wk, 2wk, 3wk, and 4wk time intervals. As a feasibility test, these measurements were taken on a mannequin at the above time intervals. Superimposition of seven 3dMD images for each facial posture per subject was performed for analysis. Two-tailed paired t-test was done for seven time points. One-way ANOVA test was conducted across the four facial postures. (α<0.05)
Results: Measurements on a mannequin confirmed the reliability of all the landmarks and parameters used in this study. For 40 subjects, 3dMD measurements between ST landmarks were reproducible with a random error lower than 1mm except for the distance from cheilion to cheilion (2.79mm). Comparing across the four facial postures, R showed the smallest variation with total average difference (TAD) (1.36mm) and SD (0.81mm). S posture had the largest variation with TAD (1.83mm) and SD (1.28mm).
Conclusions: 3dMD can perform ST analysis with both accuracy and reproducibility and can be utilized for evaluating ST changes with dental treatment. Cheilion might not be an appropriate landmark to use for ST analysis. R and MIP facial postures are recommended over smile (S or SLC) for more consistent parameter measurements.