咀嚼の主要な機能である食塊形成の過程を解明するためには, 咀嚼時の食物動態を観察することが重要である.本研究では, シリコーン印象材のパテタイプを食物に見立てて擬似咀嚼を行わせ, 咀嚼後の代用食品の形状を観察して咀嚼時の食物動態の概要について, 以下の結論を得た.
1.咀嚼中の食物は上下顎臼歯の被蓋咬頭の内斜面に沿った方向へ流出している.
2.頬, 舌の協調機能による咬合面への食物の乗せ方には, 舌側から適量つつ咬合面に乗せて咀嚼を行う分割咀嚼と, 全量を咬合面上に乗せて咀嚼を行う一括咀嚼の2通りの咀嚼様相がみられる.
3.正常被蓋側では分割咀嚼が行われ, 咀嚼機能は円滑に営まれている.
4.交叉咬合側では一括咀嚼が行われているが, これは機能的には正常とみなし難い.

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In order to evaluate the validity of Class II occlusal condition of the first molars after orthodontic treatment utilizing single-arch extraction of the upper first bicuspids, computer simulated biomechamcal analysis was carried out. Four sets of setup models were produced. The setup models represented two occlusal conditions (Simple Class II : The Class II occlusal condition with the upper first molar displaced parallel in the mesial direction from a Class I occlusal condition and Modified Class II : The Class II occlusal condition in which mesial rotation and distal angulation were applied to the upper first molar), and two types of upper first molars which differed in terms of the developments of the distal cusps (Type l: well developed and Type 3: poorly developed) . Next, the surface shapes of the setup models were recorded, and the models of the teeth and the bolus (a small mass of food) were produced for the computer simulation. A finite element analysis was applied to the models and the von Mises' stress that arose inside the bolus model was calculated as an index of destruction efficiency of the bolus.
The results were as follows:
1. For the Type 1 upper first molars no remarkable change in the von Mises' stress was recognized between Simple Class II occlusal condition and Modified Class II occlusal condition.
2 . For the Type 3 upper first molars there was a significant change in the von Mises' stress between Simple Class II occlusal condition and Modified Class II occlusal condition.

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The purpose of the present study was to investigate the coordination between the muscle activities of the masticatory, facial and suprahyoid muscles, and the action of the oral, pharyngeal and laryngeal organs in healthy subjects during chewing and swallowing barium bread. Videofluorography (VF) and electromyography (EMG) were recorded while subjects took in, masticated and swallowed the barium bread.
The following results were obtained: in the pharyngeal stage of swallowing, a monophasic wave was observed during laryngeal movement. The reproducibility was confirmed in the relationship between the laryngeal movement wave and bolus position when swallowing. The duration of muscle activity in the masticatory muscles, orbicular oris muscle and suprahyoid muscle during swallowing was significantly longer than in chewing. In the temporal relationship between laryngeal movement and muscle activities, the temporal and masseter muscles began the activities before the onset of the monophasic laryngeal movement, whereas the digastric and mylohyoid muscles were activat-ed almost simultaneously or slightly after onset.

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