In this experiment, in order to analyze the relationship between bruxism and sleep condition with swift and ease, an attempt was made to develop a biologic phenomena analyzing system that would analyze the relation between bruxism and brain wave sleep stages during sleep at night. Using a wireless telemeter (WEE-6112, WEB-5000, Nihon Koden, Japan), the EEGs, EOGs, ECGs, EMGs of masseter muscle, EMGs of mental muscle and respirogram were recorded simultaneously throughout the night. By using the sleep brain wave analyzing equipment (DEE-1100, Nihon Koden, Japan), sleep stages were determined every 30 seconds from the brain wave and classified. Bruxism was measured as the masseter muscular activities that were taken from the middle portion of the bilateral masseter muscles, had a burst that was larger than that of swallowing action taken before sleep, and either had the interval between the bursts less than 5 seconds or had a burst that lasted longer than 5 seconds.
A program in which the data of the brain wave sleep stages of every 30 seconds and the appearance of bruxism from the time one goes to sleep to the time one gets up were inputted was prepared. By using such programs it was possible to overlap display the course of the transition of brain wave sleep stages and the appearance of bruxism during sleep at night, and to visually observe the manner in which brain wave sleep stages shift due to the appearance of Bruxism. At the same time it was possible to perform quantitative evaluations such as the change of sleep stages due to bruxism, the number and frequency of appearance of bruxism at each sleep cycle, the number of bruxism at each sleep cycle and sleep stages. Thus we were able to develop a system that would quantitatively and visually evaluate the relation between bruxism and brain wave sleep stages.

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The purpose of this research was to evaluate tooth movement in six degrees of freedom under occlusal force loading. The right side upper first premolar movement of an adult volunteer without any signs or symptoms of periodontal disease was studied. A small occlusal table mounted on a force transducer was clipped between the upper and lower dentition. Occlusal force was applied to the buccal cusp, palatal cusp or central fossa of the first premolar and also to the right side canine aspect by clenching this occlusal table.
The right side first premolar movement relative to the left side first premolar was measured by means of a high-resolution six degrees of freedom motion detector. The three-dimensional shape of the first premolar was measured with following methods. A 3-D digitizer with a touch sensor probe was used to measure the coronal part of a cast stone model of the tooth. Computerized tomography data were used to obtain the root shape of the tooth. These movement and configuration data were combined to perform computer graphics analysis of the three-dimensional tooth movements. The range and direction of tooth movement were varied by altering the position and amplitude of occlusal force loading. Since the magnitude of the tooth movements was relatively small, we adapted the screw axis (helical axis) concept to emphasize tooth movement on the computer graphics representations.

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Evaluation of temporomandibular joint function in healthy children is important. The purpose of this study was to investigate characteristics of condylar movement during lateral excursion in children.
Twenty-two subjects with normal occlusion were divided into three age groups: primary dentition group (3 girls), early mixed dentition group (2 boys, 7 girls), and permanent dentition group (2 males, 8 females) . Jaw movement was measured with a 6 degrees of freedom jaw tracking device.
Jaw movement of the whole mandible was simulated on the graphic terminal. Characteristics of condylar movement in children were investigated by three-dimensional condylar path distance during lateral excursion.
The results obtained were as follows:
1. The distance of working condylar path during lateral excursion did not show significant difference between kinematic condylar point and another condylar point in children.
2. The distance of working condylar path during lateral excursion was significantly larger in children than in adults and decreased with growth.
3. The distance of working condylar path along the anterior-posterior and superior-inferior axes during lateral excursion was decreased with growth. Along the left-right axis, the distance of condylar path during lateral excursion was larger in early mixed dentition group than in other groups.
The results suggested that condylar movement in children is stabilized with growth, however, in the early mixed dentition group, lateral mobility in the condyle is apparent.

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The tooth supporting system was analyzed by a three dimensional Finite Element model of the lower premolar region in accordance with the anatomical structures and their material properties. Tooth mobility and the Fourier spectrum of its acceleration responses were calculated from the behavior of the model under static and dynamic loading. The responses of the model were consistent with that of behavior in vivo, which suggests that the model is plausible and reflects the structure and mechanism of the tooth supporting system. The results were, 1) The elastic response depends on the direction of the periodontal fiber bundles and their mechanical properties. 2) The viscosic response depends on the damping coefficient of the periodontium. 3) The frequency spectrum of a normal tooth showed two peaks at about 600 and 1600Hz. 4) The model response of an abnormal tooth presented an increasing frequency spectrum level due to a diminishing elastic coefficient, tricuspidisation of the 600Hz peak at 380, 600 and 800Hz due to a reduction of the viscosic coefficient, and tricuspidisation of the response (1600Hz peak) of the tooth, when the upper one thirds of alveolar bone was lost at 1300, 1600, and 1900Hz. These results clarified anatomical structure and material property on which the viscoelastic behavior of the periodontium depends.

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Clarifying the effects of changes in the number of occlusal contact points on occlusal function is important. In the present study, we measured occlusal forces using dental prescale films to ascertain the effects of changes in premolar occlusal contact. Subjects were seven adult males with normal occlusion. Subjects were instructed to bite a dental prescale film as hard as possible while using a maxillary bite plate (every mandibular tooth made contact with the plate), to measure occlusal forces. Next, the surface of each bite plate that came into contact with the mandibular premolars was ground so that mandibular premolars did not come into contact with the plate. Subjects were then asked to use the ground bite plate and repeat the test. The results were as follows: (1) when premolar occlusal contact was absent, the total occlusal force was significantly lower than that when premolar occlusal contact was present; (2) when premolar occlusal contact was absent, the level of occlusal forces applied to the molar region was significantly greater than that when premolar occlusal contact was present; and (3) in particular, when premolar occlusal contact was absent, the level of occlusal forces applied to the first molar region was significantly greater than that when premolar occlusal contact was present. Conversely, occlusal forces applied to the second molar demonstrated minimal change, irrespective of premolar occlusal contact. These findings suggest that premolar occlusal contact affects the distribution of occlusal forces applied to the other teeth. In particular, changes in premolar occlusal contact affect the level of occlusal forces applied to the neighboring first molar, and are involved in the expression of maximum occlusal forces.

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