Dynamic response of the adult monkey maxilla to occlusal forces

We investigated the magnitude of various maxillary occlusal forces and the direction in which such forces were propagated. Adult monkeys were anesthetized and forced to occlude on sticks of 3, 5 and 7 mm thickness at the canines, second premolars and second molars. Electrical stimulation was applied to the masseter and temporalis muscles, and measurements of magnitude, direction and character of principal strains were recorded. Readings for the surface of the maxilla indicated that bone sutures and adjacent cavities are intimately and functionally related to the buffering of these occlusal forces. The maxilla deformed as the premaxilla was pushed out in the region of the premaxillomaxillary suture. The nasal bone was stretched anteroposteriority in the region of the nasomaxillary suture as the space that arose due to contraction of the masseter muscle was filled in the region of the zygomaticomaxillary suture. In addition, when occlusal forces were imparted on the maxilla, the surfaces of this bone bulged out due to the effect on adjacent bone cavities. Results demonstrated that the maxilla dispersed occlusal force well by these mechanisms. Accordingly, there were very few regions in this bone where stresses concentrated.