A new navigation system based on cephalograms and dental casts for oral and maxillofacial surgery

Intraoperative navigation systems help surgeons to accurately carry out preoperative plans without injuring anatomically important structures. A system is evaluated that uses cephalograms instead of computed tomographic (CT) scans to create images. Three-dimensional (3D) dental casts provide registration between imaging data and the patient. Cephalograms are widely employed in orthognathic and oral and maxillofacial surgery and expose patients to lower doses of radiation than CT. The system uses a dental cast to register the operation field to a pair of frontal and lateral cephalograms. The cast is transformed to 3D data with a laser scanner and a programme that runs on a personal computer. 3D data describing the dental cast, cephalograms and the oral and maxillofacial region of the patient are integrated with specialized software. The optical tracking system for navigation uses charged-coupled-device (CCD) video cameras and light-emitting diodes (LEDs). Two CCD video cameras follow the 3D coordinates of LED assemblies attached to the head, lower jaw and a handpiece. Errors occurring when a dental cast was transformed to 3D data ranged from 0.08 to 0.21 mm. Mean errors were 0.71 mm (0.21-1.09 mm) for the right maxillary central incisor, 0.62 mm (0.04-1.69 mm) for the right maxillary 2nd molar and 1.02 mm (0.23-1.47 mm) for the left maxillary 2nd molar. This surgical navigation system is sufficiently accurate for use in oral and maxillofacial surgery.