Dynamic response of the vertebral arch laminae during unilateral occlusion

Inoue Satoshi, Kawamoto Tatsuo

doi:10.18905/shikaigaku.63.3_2

In order to evaluate the relationship of the hickness of the substance being chewed, occlusal force, and deformation of the cervical vertebrae, we measured deformation of the left and right lamina of the vertebral arch of monkeys from the first to third cervical vertebrae. This was done by electrically stimulating the anesthetized animal's bilateral masseter muscles to in-duce the left first molars to occlude on 3 and 7 mm thick chips of wood with mild, intermediate, and strong force. Because the head tilts toward the working side when the animal bites a 3mm thick chip of wood with the first molars, the working side of the first cervical vertebra is strongly compressed and the nonworking side extends vertically. The amount of deformation on the sorking side of the second cervical vertebra was very small, and the direction of deformation varied with the biting conditions. There was significant extension vertically on the working side and this tendency became marked with increases in induced occlusal force. When the animals occluded on a 7mm thick chip with the first molars, this tendency became more pronounced, and the nonworking side of the second cervical vertebra was markedly deformed in the horizon-tal plane. As the thickness of the chip and the occlusal forces increased, the first cervical verte-bra tended to incline toward the working side, while the second cervical vertebra inclined toward the nonworking side to compensate for the inclination of the first cervical vertebra. Because this phenomenon is mediated by the odontoid process of the second cervical vertebra, it is clear that the odontoid process plays an extremely important role in maintaining posture during occlusion and mastication.

Dynamic response of the vertebral arch laminae during unilateral occlusion

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