A proposal for soft tissue landmarks for craniofacial analysis using 3-dimensional laser scan imaging

To evaluate the accuracy of the 3-dimensional laser scanner and to propose reproducible soft tissue landmarks in the 3-dimensional facial images.

A mannequin head was preliminarily scanned 6 times to calculate scanning errors. Mean errors in the linear measurements from the scanned images and the actual mannequin head were assessed and the magnification rate of the scanned images was calculated. The soft tissue landmarks were defined in the mannequin head and the patients with normal, Class II, and Class III malocclusions. The reliability and the reproducibility were investigated by comparing the x-, y-, and z-coordinate of each landmark gained from repeated landmarking procedure.

Scanning errors were 0.16 mm in the x axis, 0.15 mm in the y axis, and 0.15 mm in the z axis. The mean error of scanned image was 0.37 mm and the magnification rate was 0.66%. In the four 3-dimensional images, the standard deviations in the localization of all landmarks were less than 1.0 mm in the x, y, and z axes.

The laser scanner is a useful tool for understanding the 3-dimensional facial structure, and the soft tissue landmarks proposed in this study were considered highly reproducible and reliable.