Recording of mandibular movements by intraorally placed light emitting diodes.

In order to evaluate an opto-electronic system for recording mandibular movement a simulator and clinical pilot study was performed. The method was based on light emitting diodes (LED) and a photodetector system. One LED was placed intraorally and one on the forehead, the latter acting as reference. When the light spot is focused on the detector surface a photo-current will occur. This current can be used to obtain two signals linearly related to the x and y coordinates of the LED. By using two detectors the three-dimensional coordinates of a movement can be calculated, consequently also the z-coordinate. In the simulator experiment the method was shown to have a satisfactory precision and good reproducibility. The results from the clinical test indicated that it is possible to measure and record mandibular movement with a minimum of external influence to the test person.