Reproducibility of soft tissue landmarks on three-dimensional facial scans

This study evaluated the reproducibility of 24 soft tissue landmarks on six three-dimensional (3D) facial scans. The scans were taken on a DSP400 facial scanner and were viewed using a customized software program. Intraoperator data were obtained by one researcher placing the 24 landmarks on all six scans a total of 30 times. Thirty different orthodontists of varying experience were then asked to place all 24 landmarks on each of the six facial scans in order to establish interoperator reproducibility. The standard deviations (SDs) from the mean were calculated from the data for each individual landmark in the x-, y-, and z-axes. For the intraoperator data, 12 of the 24 landmarks were found to be reproducible to within a 1 mm SD for each plane of space. The interoperator data showed lower reproducibility with just two landmarks showing less than a 1 mm SD in all three planes of space. Familiarity with 3D facial scans and associated software programs is important in improving reproducibility. In addition, the landmarks investigated in this study included those not often used. It is suggested that landmarks showing poor reproducibility for both inter- and intraoperator data should be avoided, if at all possible, or at least used with caution.