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维度意外变化的调节作用。8名健康受试者使用装置改变垂直闭合位置，以恒定的咬合力进行重复的颌骨开合动作。垂直闭合位置增加后，第一次试牙的最大咬合力大于第二次或第三次，但垂直闭合位置降低后，第一次试牙的最大咬合力小于第二次试牙。结果表明，在改变垂直颌骨关闭位置后的头两到三次试验中，这种调制似乎几乎完成(Tanaka等人)。接下来，我们通过实验再现了咀嚼过程中食物硬度不可预测的变化情况，分析了咬合力的控制。在试验过程中，7名健康受试者被指示进行重复的颌骨开合运动，并保持恒定的咬合力。最大咬合力和冲量受到硬度变化的显著影响，而硬度的增加会导致最大咬合力和冲量的值增加，之后这些值保持不变，而受试者咬合相同的硬度水平。这些结果表明，所产生的咬合力的水平是根据被咀嚼食物的硬度自动调节的。我们得出结论，当食物的硬度发生不可预测的变化时，可以采用咬合力来进行有效的咀嚼(Shimada等人。在新闻发布会上)。

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).