[3-D imaging of the facial surface by topometry using projected white light strips]

Three-dimensional registration of the facial surface by methods which are currently in use is difficult because of the long measuring times required by point-based imaging systems. Artifacts caused by movement appear, e.g., blinking. Also the production of a facial plaster-cast model for measuring is not an adequate solution. In order to acquire data of the facial surface in a contact-free manner, a system is needed that has short measuring times, is able to record data of complex surfaces and at the same time does no harm to the open eyes. The method described here represents a new development of an industrial high tech CAD/CAM system. Unlike customary point-based imaging systems, the stripe projection method works using entire planes. Structured light is aimed at the surface to be measured, recorded by videocamera and calculated by triangulation; then the different views are combined by computer. The system has an optic sensor that can record approximately 500,000 measuring points within seconds (ca. 1.7s). Test persons' faces and plaster-cast models of them (n = 15) were measured comparatively and serially (n = 5) to test the validity and reliability of the method for maxillofacial procedures. These investigations show that this method is appropriate for recording three-dimensional soft-tissue profiles. First studies on patients before and after dysgnathia operations were undertaken. A prospective long-term study for collecting data on pre- and postoperative dysgnathia patients has been begun. Initially, it will record the changes in facial soft tissue on the basis of skeletal displacement. Later, predictions about the soft-tissue changes subsequent to dysgnathia surgery can be worked out on the basis of stored data matched with three-dimensional bone data.