A ROBOTIC SYSTEM FOR TESTING DENTAL IMPLANTS

Previous studies have attempted to predict the manner in which potenti ally harmful levels of force are transmitted to human bone surrounding dental-implants and adjacent teeth. However, the analysis models prev iously used are dependent on unknown biomechanical behaviors. In order to develop in vitro testing to measure the force transmission between dental implants and attached prostheses, an accurate simulation of th e chewing motion is crucial for data validation. This paper proposes a new approach involving a robot simulation system. The system has been designed to produce simulated mandibular movements and occlusal conta ct forces so that various implant designs and procedures can be thorou ghly tested and evaluated. This paper describes the various components and operation of the test apparatus, including sample results. The pr imary components of the system are a robot, a test fixture and a measu rement system. The robot is a commercially available robot with four p rimary degrees of freedom. The current technique used to teach the rob ot mandibular motion trajectories is based on the use of a dental arti culator (Wang et al., in Proceedings of the 4th National Applied Mecha nics and Robotics Conference, AMR95-094, 1995)[1]). The articulator is then;replaced by the actual test specimen consisting of a simulated l ower jaw mounted to the robot base and a simulated upper jaw mounted t o the robot end effector. A set of noncontact displacement probes are used to measure lower jaw-implant deformations during simulated chewin g. A multi-axis force-torque sensor is mounted on the end effector for measurement and feedback of overall force levels, and a system of str ain gages is used to ascertain force levels transmitted by individual teeth. Multi-tooth dental bridges consisting of combinations of natura l teeth and implants are the primary focus of the research. The object ive is to determine the manner in which overall force levels are distr ibuted during various chewing cycles. This information will be useful in understanding the manner in which potentially harmful levels of for ce are transmitted to human bone surrounding dental implants and adjac ent teeth by providing more accurate force input data for finite eleme nt models which are under development. The use of a robotic system for generating motion and force transmission patterns will facilitate the standardization of procedures in evaluating implant designs. (C) 1998 Elsevier Science Ltd.