[A study on mandibular displacement due to biting force. 2. Analysis of condylar displacement]

Part of the biting force is believed to be transmitted to the temporomandibular joint and cause interarticular pressure. This pressure's degree and function, however, are not clarified. In this paper, I shall examine this pressure from condylar movement measured by the face-bow. For the measurement of condylar movement caused by biting-pressure, I used an intraoral appliance which consisted of a pair of Co-Cr clutches and a pivot. While the patient exerted both maximum and medium biting force on the pivot located at the first molar, mandibular movements were measured. Both sides of the condyle tended to move anterosuperiorly. Condylar movement averaged 0.29 mm on the working side, and 0.46 mm on the balancing side during maximum bite force. Distance and direction of the condylar movements were equal to the results of previous investigations, excepting the direction of working side condyle. The difference was considered to be primarily due to experimental variables. The condylar movement during biting was smaller than that during pushing the jaw upward with manual forces. This suggests that interarticular pressure is only slight on both sides during first molar bite action.