Objective:To compare two digital methods of quantitatively accessing the degree of facial asymmetry by three-dimensional data.Methods: The three-dimensional data of 20 subjects were got by the FaceScan, and then were input to the reverse engineering software Imageware 13.0 and Geomagic 12 .Their mirror data were acquired and superimposed with the original data by the methods of interactive closest points ( ICP) and Procrustes analysis ( PA) .The mid-sagittal planes of the two methods were ex-tracted respectively, the degree of facial asymmetry and the distance of 21 automatic landmarks to mid-sagittal plane were calculated and compared.Results:The paired t test was taken and t=1.346, P=0.193.Conclusion:We can safely come to the conclusions that for the subjects with no evident facial asymmetry, there are no significant difference between the PA and the ICP methods for extracting the mid-sagittal plane from three-dimensional data.

Objective:To evaluate the actual measurement accuracy of 2 three-dimensional(3D)facial scanners for real person. Methods:3D digital face models of 1 0 volunteers with normal ficial form were obtained by 3dMD and FaceScan facial scanners respec-tively.The measurement values of 1 0 feature lengths and 5 feature angles were measured on each 3D model by the software respective-ly.The reference values of all characteristics were acquired by line laser scanner (Faro)with high accuracy.Statistical and surveying analysis were taken between the measurement values and reference values.Facial morphology measurement error and actual accuracy of facial scanners were obtained finally.Data were statistically analysed.Results:The length measurement accuracy of 3dMD and FaceS-can was(-0.37 ±0.68)mm and (-0.29 ±0.53)mm(P =0.223),the angle measurement accuracy was (-0.22 ±2.1 4)°and (0.1 2 ±2.69)°(P =0.428),respectively.Conclusion:The 3D data of ficial morphology obtained by the 2 scanners are not signifi-cantly different.