Three-Dimensional Accuracy of Facial Scan for Facial Deformities in Clinics: A New Evaluation Method for Facial Scanner Accuracy.

In this study, the practical accuracy (PA) of optical facial scanners for facial deformity patients in oral clinic was evaluated. Ten patients with a variety of facial deformities from oral clinical were included in the study. For each patient, a three-dimensional (3D) face model was acquired, via a high-accuracy industrial "line-laser" scanner (Faro), as the reference model and two test models were obtained, via a "stereophotography" (3dMD) and a "structured light" facial scanner (FaceScan) separately. Registration based on the iterative closest point (ICP) algorithm was executed to overlap the test models to reference models, and "3D error" as a new measurement indicator calculated by reverse engineering software (Geomagic Studio) was used to evaluate the 3D global and partial (upper, middle, and lower parts of face) PA of each facial scanner. The respective 3D accuracy of stereophotography and structured light facial scanners obtained for facial deformities was 0.58±0.11 mm and 0.57±0.07 mm. The 3D accuracy of different facial partitions was inconsistent; the middle face had the best performance. Although the PA of two facial scanners was lower than their nominal accuracy (NA), they all met the requirement for oral clinic use.

[Evaluation of measurement accuracy of three facial scanners based on different scanning principles].

OBJECTIVE: To evaluate and compare the measurement accuracy of three facial scanners, based on different scanning principles: line laser, structured light and stereophotography. METHODS: Three-dimensional (3D) digital face models of the same plaster head model were obtained by three facial scanners separately. The measurement values of the length of 10 feature lines and the angle of 5 feature angles were measured on these 3D models in the software respectively. The standard values of these characteristics were measured by a coordinate measure machine (CMM) with high accuracy. Statistical and surveying analyses were made between the measurement values and standard values. Facial morphology theory measurement accuracy of these three facial scanners was obtained finally. RESULTS: There was no statistical significant difference between the measurement values from the three facial scanners and the standard value from CMM. The 3dMD and Faro scanners were better in length measurements and the length measurement accuracy was about 0.2 mm. The Faro scanner was also better in angle measurements and the angle measurement accuracy was about 0.5°. CONCLUSION: The three facial scanners all have good reliability in facial measurements, and their actual measurement accuracy for patients needs further research.