Regulation of occlusal force due to hardness-change of the bite object

首先，我们研究了咬合力对咬合垂直尺寸意外变化的调制。使用一种装置来改变垂直的颌骨闭合位置，8名健康受试者被指示进行重复的颌骨开合运动，恒定的咬合力。增加垂直合颌位后，第一次试验的峰值咬合力大于第二次或第三次试验，但减少垂直合颌位后，第一次试验的峰值咬合力小于第二次试验。结果表明，在改变垂直颌闭合位置后的前两次或三次试验中，这种调制似乎几乎完成（Tanaka et al. 2006）。接下来，我们通过实验再现在咀嚼过程中食物硬度发生不可预测变化的情况，分析咬合力的控制。7名健康受试者被指示进行重复的下颌开合运动，并在整个试验过程中保持恒定的咬合力。峰值咬合力和冲量的显着影响的硬度的变化，而硬度的增加引起的峰值咬合力和冲量的值增加对指令，之后这些值保持不变，而受试者闭塞相同的硬度水平。这些结果表明，根据咀嚼食物的硬度自动调节咬合力的水平。我们的结论是，当食物的硬度发生不可预测的变化时，咬合力是有效咀嚼的关键。

First, we investigated the modulation of occlusal force to unexpected changes in the occlusal vertical dimension. Using a device to change the vertical jaw closing position, eight healthy subjects were instructed to perform repetitive jaw open-close movements with constant occlusal force. The peak occlusal force was greater in the first trial than that in the second or third trial after increase in the vertical jaw closing position, but it was smaller in the first trial than in the second trial after a decrease in the vertical jaw closing position. The results indicate that this modulation appears to be almost completed in first two or three trials after change in the vertical jaw closing position (Tanaka et al. 2006).Next, we analyzed the control of occlusal force by experimentally reproducing situations in which the hardness of food changed unpredictably during mastication. Seven healthy subjects were instructed to perform repetitive jaw open-close movements and to maintain constant occlusal force throughout the trial. Peak occlusal force and impulse were significantly affected by the change in hardness, while an increase in hardness caused increase in the values for peak occlusal force and impulse against the instruction, after which those values remained constant while the subjects occlude the same level of hardness. These results indicate that the level of the resulting occlusal force is regulated automatically according to the hardness of the chewed food. We concluded that occlusal force was adopted for efficient mastication when the hardness the hardness of food changes unpredictably (Shimada et al. in press).