An artificial oral environment for testing dental materials

An artificial oral environment which closely matches the conditions of human mastication for dental materials testing is described. Two servo-hydraulic actuators were combined to produce the force movement cycle of human mastication. A closed-loop method of control which functions in a manner similar to the human neuromuscular system was used. The horizontal closed loop used a linearly variable differential amplifier (LVDT) to monitor the position. The vertical closed loop used an LVDT to monitor position and a load cell to monitor force, with a ´mode switch´ being made between the two mechanisms of control. A function generator was used to produce a sinewave that was modified to produce the movement and force programs for the two servo-hydraulic actuators. An acrylic chamber which contains the test samples and maintains an environment similar to that of the mouth was constructed. Natural or artificial saliva maintained at 37 degrees C is continuously circulated through the chamber. The time to complete a single chewing cycle was decreased by eliminating that part of the cycle where no force is produced. This enables the chewing rate to be increased to 4 cycle/s. The wear produced in the artificial mouth was found to have a high correlation with clinical wear if 250000 cycles in the artificial mouth are assumed to be equivalent to one year in the human mouth.