The purpose of this research is to clarify the feature of a chewing movement, especially during occlusal phase, in children with primary dentition. Two groups of subjects were used; children with primary dentition (20 children) and adults with permanent dentition (32 females) . Gum chewing motion of the mandible of each subject was measured using a TRIMET^®, which can three-dimensionally analyze the simultaneous movements of multiple points on the mandible of a subject. A series of chewing motions were divided into its component cycles, and then chewing patterns were analyzed and compared between two groups. As results, the chopping type was dominant in children, however, it was the grinding type in adults. Also more than 30% of cycles in children were reverse type. The pathway of the movement had relatively larger anterior-posterior and smaller lateral ranges in children compared with adults. Longer occlusal contacts were suggested on the opening stroke than the closing in children. The underlying reason for these findings may be due to physiological growth, maturation, and adaptation of the occlusal function.

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Adjustable articulators are divided into two classes based on the guiding systems of them, the Arcon type and the Condylar type. However, it seems particularly inappropriate to use these classifications when it comes to the reproduction of the lateral movement on the articulator. The object of this study is to classify the adjustable articulators according to the Arcon and the Condylar type guiding systems. We theoretically classified the adjustable articulators into eight groups according to their guiding systems. It has become clear that the articulators under discussion can be divided into three groups by using this method: Type II: articulator with Box type joint guiding mechanism, Type IV and VI: articulators with Slot type joint guiding mechanism.

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‹Objective› The objective of this study was to examine how denture wearings after tooth loss would have an influence on oral transit in oropharyngeal swallowing.
‹Methods› Data were analyzed in nine young dentates (24.9± 1.7ys) and nine denture wearers (66.4±6.5ys) . Subjects were instructed to masticate ten grams of steamed rice, then swallow in one time when food was cut into smaller pieces and softened by saliva. Tongue movement, up and down tongue dorsal movement at the region of first molar, was examined by ultrasonography (TOSHIBA, SSA-250A) . Recordings of mandibular movement using Mandibular Kinesiograph (Myotronics, K6- I ) and muscular activity of infrahyoid muscles on both sides using surface electromyography were performed simultaneously. Measurement points were decided as the onset of oropharyngeal swallowing, the onset of bracing activity by the teeth and the onset of muscle activity. Timing of events was calculated. A statistical analysis was performed with use of Mann-Whitney test in comparison between two groups. ‹ Results and discussion › The typical records were as follows: one or two times peaks of tongue movement record were observed (down and up movement of tongue), then tongue movement stopped (press tongue against the palate) . The last peak is considered the onset of propelling bolus posteriorly, or the initiation of oropharyngeal swallowing. Mandibular movement tracks became a state near to intercuspal position (bracing activity by the teeth) . Two or more continuous muscle activities were observed. Finally, tongue and mandibular movement stopped at the rest position. Muscle action potential on both sides returned to the base line.
When time 0 was defined as the onset of muscle activity. The onset of tongue movement propelling posteriorly in denture wearers was earlier than in young dentates (p<0.05) .
‹Conclusions›
1. Noninvasive examination of oral transit during oropharyngeal swallowing was performed.
2. The onset of oral transit followed the onset of bracing activity by the teeth in all subjects.
3 . It was suggested that denture wearings after tooth loss would have an influence on the initiation of oropharyngeal swallowing.

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In order to clarify the control mechanisms of temporomandibular joint (TMJ) loading during a static bilateral bite, we have been numerically analyzing the controllability of TMJ loading through coordinative activities of the masticatory muscles, employing a static two-dimensional (2-D) jaw model, which consists of a rigid-body model of the jaws with a rigid-body spring model of the TMJ and masticatory muscles, such as the masseter, the anterior portion of the temporalis and the lateral pterygoid. These muscles were all simulated as force vectors applied to the mandible. Bite force was applied to a single point on the lower first molar, and its direction was set so as to be perpendicular to the occlusal plane. Numerical simulations verified that TMJ loading can be minimized by simply adjusting the activities of the masseter and temporalis muscles. The direction of the minimum TMJ-loading vector nearly agrees with the direction from the intermediate zone of the ariticular disk to the condylar center. Our previous model, however, neglected the digastric muscle, even though it functions during a bilateral bite. This paper then attempts to analyze the effects of the digastric force on the afore-mentioned controllability of TMJ loading, employing an updated jaw-model that includes the digastric muscle. Through numerical experiments, the activation of this muscle was verified to slightly increase the minimum TMJ-loading and to be completely independent of the direction of the minimum TMJ-loading vector. Thus, the digastric muscle is believed to play no significant role in the control of TMJ loading, and its activation had no discernible effect on our previous findings, with respect to the minimization of TMJ loading.

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Some patients complains tongue discomfort or inadaptation to newly inserted prosthesis. When treating the patient who takes in a delicate change of a occlusal relationship or an outline form of dental prosthesis, it would be of great importance to prepare an quality oral rehabilitation in harmony with stomatognathic function after the complaint is fully cared.
We have been successful in providing treatment for those patient with highly keen oral sensory complains by using a double-casting method that could provide not only functionally generated path during both function and parafunction but also precise outline form which adapt to surrounding soft tissues. This procedure could eliminate several major source of the technical errors in cast restoration, which would affect the occlusion of the crown and bridge prosthesis. This method can eliminate the error caused by the distortion of the cast of opposing teeth, the error of the occlusal registration, the error in mounting casts on the articulator, the error caused by the fitness to the abutment tooth and the error caused by the proximal contact with adjacent tooth. All these errors could be eliminated with this double-casting method, because these errors could be compensated by the fitting procedure of the base crown prior to the molding of occlusal structure. The prosthesis produced by this method usually needs no adjustment on the final setting.
Reporting one clinical case treated using this method, detailed procedure for this method was introduced.

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