Real-time sensing of tooth position for dental digital subtraction radiography

Dental digital subtraction radiography and accurate repositioning of the patient and X-ray source in order to facilitate correct diagnostics of bone loss are considered. Present mechanical repositioning systems do not allow radiography of posterior teeth and are uncomfortable for the patient. A repositioning system having a six degree-of-freedom position sensor and a robot arm with an X-ray source is proposed. A mathematical model for the system is given, and the robot arm solution is obtained based on patient position. An error analysis is performed in order to determine the influence of sensor and robot errors on system accuracy. A series of experiments to determine sensor noise and accuracy are described. These tests showed relatively small errors over the work envelope of the sensor. Further tests showed that there is no adverse effect due to the presence of metal work in the patient´s mouth. The high bandwidth of the sensor may allow real-time tracking of small movements of the patient´s head.