In order to evaluate masticatory function of patients wearing removable denture, the patterns and stability of masticatory path were analyzed.
 The movement of mandibular incisal point of 12 patients wearing removable denture chewing gummy-jelly for 20 seconds on their habitual chewing side was recorded by a MKG K6I. First, for all subjects the average path and the overlap of the path movement were displayed for the ten cycles between the fifth cycle and the fourteenth cycle. The movement path was classified into one of 7 patterns and the frequency of each pattern were calculated and compared between before treatment and after treatment. Next, 3 indicators representing the stability of the movement path, that is, the SD/OD (standard deviation/opening distance) of lateral component of opening, lateral component of closing and vertical component, were compared the two.
 Before treatment most patients showed various patterns of masticatory path, but after treatment the majority showed path patterns that were typical of healthy normal person with natural dentition. A statistically significant difference was found between the two. The SD/OD of lateral component of opening, lateral component of closing and vertical component were much smaller after wearing new removable denture, and statistically significant differences were found between the two.
 From these results it was concluded that the masticatory function of patients needing new removable denture improved greatly after wearing new removable denture, and that analysis of patterns and stability of path movement can be applied to evaluating masticatory function.

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The purpose of this experiment was to evaluate masticatory function of patients wearing removable dentures. The masticatory performance and masseter muscular activities before and after treatment were analyzed.
 The masticatory performance and masseter muscular activities of 12 patients wearing removable denture chewing gummy-jelly for 20 seconds on their habitual chewing side were recorded. The amount of glucose extraction from chewing gummy-jelly was measured by blood glucose testing device as the indicator for masticatory performance. The cycle time and the integral value of the ten cycles from the fifth to the fourteenth cycle of chewing were calculated for masseter muscular activities. Then the average value and the coefficient of variation of cycle time and the integral value per cycle were calculated. The results were compared between before and after treatment.
 The amount of glucose extraction and the integral value per cycle were greater after wearing new removable denture, and statistically significant differences were found between the two. The average value and the coefficient of variation of the cycle time were smaller after wearing new removable denture, and statistically significant differences were found between the two.
 From these results it was concluded that the masticatory performance of patients needing new removable denture improved greatly after wearing new removable denture, and that method of measuring the amount of glucose extraction from gummy-jelly chewing can be applied to evaluating masticatory performance.

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The objective of this study was to clarify the characteristics of lip-closing force (LCF) measured by the novel developed multidirectional LCF measurement system and evaluate the relationship between LCF and physiques or physical strengths in the early stage of permanent anterior teeth occlusion. In 242 primary school children (136 boys, 106 girls, mean age = 10.3 ± 0.3 years), LCFs in eight directions during maximum voluntary pursing-like lip closure tasks, height, body weight, handgrip strength and bite force were recorded in two primary schools in Nagano as field research. The gender difference of summed values of LCFs for all eight directions (total lip-closing force [TLCF]), the correlation between TLCF and each directional LCF (DLCF), between opposing DLCFs and between TLCF and height, body weight, handgrip strength and bite force were statistically analyzed. TLCF in boys was significantly greater than that in girls. The DLCFs was large by vertical, oblique and horizontal directions order. There were significant correlations between TLCF and DLCFs except horizontal directions and between most pairs of opposing DLCFs. Symmetrical outputs in most pairs of opposing DLCFs were also observed. In girls, there were significant correlations between TLCF and height, body weight, handgrip strength or bite force, however in boys, there were significant only between TLCF and body weight or handgrip strength. In the early stage of permanent anterior teeth occlusion, LCF showed unique directional specificity in vertical, horizontal, oblique and opposing directions. And the present results suggested that LCF was related to the ability for volitional movement.

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In order to clarify the effect of the taste of food on the masticatory movements, 16 healthy subjects, aged 22 to 28 years (average age 25.8 years) were asked to chew gummy-jelly of different flavors and their masseter muscular activities were investigated. Three types of gummy-jelly with varying degrees of bitterness ranging from, not bitter, slightly bitter, to bitter were chewed on the habitual chewing side for 20 seconds and the masseter muscular activities on the habitual side were measured by EMG. After the masseter muscular activities were observed, the duration, interval and cycle time of the masseter muscular activities, the integral value of all cycles and the integral value per cycle were calculated and compared among the three foods. The duration, interval, and cycle time of the masseter muscular activities was the shortest during chewing non-bitter gummy-jelly and increased with the degree of bitterness of the gummy-jelly. Statistically significant differences were found between chewing of non-bitter and bitter gummy-jelly. However, no significant difference was found in the total integral value and the integral value per cycle of the masseter muscular activities. From these results it was concluded that the difference in the degree of bitterness of the gummy-jelly affects the chewing rhythm, but does not affect the amount of the masseter muscular activities.

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Purpose: Rhythmic Masticatory Muscle Activity (RMMA) is rhythmic jaw movements similar to mastication approximately at 1 Hz during sleep, and it accounts for a large part of sleep bruxism. The purpose of this study was to clarify characteristic of EMG bursts of RMMA in bruxers.
Methods: Thirty bruxers who fitted the clinical diagnostic criteria of ICSD-2 of AASM participated in this study. EMG activities of the right masseter muscle were recorded during sleep at home by means of an ultraminiature electromyogram measurement system. After selecting RMMA with the threshold of amplitude of 20% MVC, we analyzed only phasic bursts whose maximum amplitude was more than 20% MVC.
Results: The mean value of the number of phasic bursts in RMMA per hour of sleep for each subject was 19.4. The mean value of the number of phasic bursts in RMMA per episode was 6.1. The total subjects' mean value of the mean values of duration of phasic bursts for each subject was 0.72 sec. Bursts with durations of 0.4-0.5sec were the most frequent of all phasic bursts that composed RMMA and the peak of distribution of burst durations shifted to the left with broad right foot. EMG bursts with maximum amplitudes of 20-30% of MVC were the most frequent of all phasic bursts in RMMA and distribution of maximum amplitudes of the bursts showed broad foot toward the right. In 80% of the subjects, the mean values of maximum amplitude of phasic bursts for each subject were less than 50% MVC.
Conclusion: This study clarified that the distributions of duration and amplitude of phasic bursts that composed RMMA with the threshold of amplitude of 20% MVC have each mode. On the other hand, it was also demonstrated that the distributions have wide ranges and variety of RMMA phasic bursts was suggested.

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