Advanced surface-recording techniques for computer-assisted oral and maxillofacial surgery.

Markerless recording of patients based on natural anatomical surfaces makes planning of computer-assisted surgery much easier, as it is not necessary to place and measure markers. Recording of the surgical site with a laser scan takes the place of conventional marker-based recording. We have used auricles as well as the maxilla and mandible as reproducible surfaces. The geometric congruence of the laser scanned surface with the corresponding surface in the computed tomographs data-set and the applied intraoperative accuracy after recording with a laser scanner have been evaluated, and the system was successful in the maxilla (mean precision: 0.8mm, standard deviation: 0.3mm). In the mandible, the tongue and mobile floor of the mouth led to geometric incongruence and inadequate laser scanning. An exact recording using auricles was possible only as long as the auricles had not been temporarily deformed by the head support during CT imaging.