Properties of biomechanics and muscle architecture in human masseter and temporolis / 实用口腔医学杂志

ABSTRACT

Objective: To study the architectural features and the biomechanical properties of human masseter and temporolis muscles. Methods: The architecture parameters of masseter and temporolis muscles on both sides of 5 human corpes fixed in formalin for more than 1 year were measured and quantitatively analyzed. Results: Human masseter and temporolis muscles were multipennate, there existed many layers of aponeurosis to which muscle fibers attached especially within the superficial portion of the masseter. The parameters of superficial portion of the masseter were statistically different from those of the deep portion, so were those of anterior portion of temporolis from those of posterior portion; the posterior part of the temporolis was the heaviest, the deep of the masseter the lightest. The physiological cross-sectional area of the superficial part of masseter was the largest, the posterior of temporolis the second, the anterior of temporolis the third, and the deep of the masseter the smallest. Among the ratios of muscle weight vs physiological cross-sectional area in each portion of the masseter and temporolis, the ratio in the deep part of masseter was the largest, that in the posterior of temporolis the smallest, that in the superficial of the masseter was similar to that in the anterior of the temporolis. In addition, the fiber in the posterior of the temporolis was the longest and that in the deep of the masseter the shortest. Conclusion: The deep portion of masseter is designed for force production, the posterior of the temporolis for velocity production, and the superficial of the masseter and the anterior of the temporolis for both force and velocity production. The deep part of masseter and the anterior of temporolis play an important part in maintaining mandibular position and balence, and the superficial of masseter and the posterior of temporolis play a major role in producing occlusive force and mandibular fast retrusion.