The measurement of mandibular movement permits a subjectspecific dynamic analysis (1) and is useful for the diagnosis of oral disorders and for designing the functional occlusal surfaces of dental prostheses (2). Furthermore, mandibular movement data can be utilized to evaluate the outcomes between before and after prosthodontic treatments and can be critical to predict the prognosis of oral rehabilitation (3, 4). A threedimensional (3D) mandibular movement device is ideal for tracking the condylar and incisal inclination movements. These devices include the magnetometry (Mandibular kinesiograph) and optoelectronic tracking systems (Sirognathograph) (5, 6) , and the Gnathohexagraph (Gnathohexagraph III, JM-2000, GC, Tokyo, Japan) , which is an optoelectronic jawtracking system with 6 degrees of freedom. These devices can measure mandibular movements during mastication using cameras to track the spatial position of lightemitting diodes (7). However, these devices are often not available in clinics because of its high cost in general, (8) , and complex to handle in daily clinical practice. Therefore, a simple, acceptable, and reliable device to measure mandibular movement is needed by clinicians. The anterior deprogramming device (ADD) , also known as the Lucia Jig, comprises an individually fabricated anterior guide table, which allows for mandibular Correspondence to:
The tooth surface fatigue strength of the conical involute gear is evaluated in this paper. Test gears are straight intersecting-axis conical gears. The material of the test gear is normalized steel. The power circulating testing machine is used in this experiment. The circulating torque is kept constant and the number of times of contact is 107. The tooth surface life is evaluated by the pitting area rate. The critical value of the circulating torque is found between 147 N·m and 157 N·m. For critical torque, the pitting area rate does not progress over 4%. The Hertzian contact stress of the test gear is calculated at the circulating torque. The contact stress should be evaluated in consideration of the wearing effects.
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