Design of realistic chewing trajectory for dynamic analysis of the dental prosthesis

Purpose: The chewing trajectory in the dynamic analysis of dental prosthesis is always defined as a two-segmental straight polyline without enough consideration about chewing force and motion laws. The study was aimed to design a realistic human chewing trajectory for the dynamic analysis based on force and motion planning methods. Methods: The all-ceramic crown restored in the mandibular first molar was selected as the representative prosthesis. Firstly, a dynamic model containing two molar components and one flat food component was built, and an approximate chewing plane was predefined. According to the desired forces (25 N, 150 N and 25 N), three force planning points were calculated by using tentative trajectories. The motion planning was then executed based on four-segment cubic spline model. Finally, the new trajectory was re-imported into the dynamic model as the displacement load for evaluating its stress influence. Results: The maximum lateral velocity was 26.81 mm/s. Besides, the forces in the three force planning points were 14.11 N, 126.75 N and 13.56 N. The overall repetition rate of chewing force was 77.21%. The force and stress profiles were similar to the sine curve on the whole. The maximum dynamic stress of the crown prosthesis was 398.5 MPa. Conclusions: The motion law was effectively brought into the chewing trajectory to introduce the dynamic effect. The global force performance was acceptable, and the force profile was more realistic than the traditional chewing trajectory. The additional reliable characteristic feature of the stress distribution of the dental prosthesis was observed.