Optical sensing does away with dental impressions

"The 3d coordinates of the tooth surface can be determined on the basis of measurements taken in the patient's mouth," says Dr Peter Kühmstedt, group manager for 3d measurement technology at Fraunhofer IOF in Jena. Under a contract from German dental company Hint-Els, a Fraunhofer team developed an optical digitisation system which scans the oral cavity and captures 3d teeth data using camera optics. A complete picture of the individual tooth is created from several data records. After an all round measurement, say the researchers, it is possible to represent the complete jaw arch as a virtual computer image. The measurement conditions in the confined oral cavity are, however, unfavourable. To obtain precise results, the scientists use fringe projections – where a projector shines strips of light on the tooth area to be measured. From the phase shifted images, the evaluation software determines the tooth's geometric contour data. Two camera optics provide the sensor chip with image information from different measurement perspectives. After pixel precise comparison of various camera images, the evaluation program recognises image faults and removes them. To avoid problems being introduced by the patient moving, each measurement position is captured in less than 200ms.