Surface EMG analysis during dynamic movement has a variety of applications, including basic reserches, biomechanics, bioengineering, rehabilitation, and sports science. However, we cannot always apply the signal processing methods developed under stationary conditions to EMG signals during dynamic movement. This article, first of all, describes the merits of a multichannel array electrode for measuring surface EMG signals during dynamic movement, to avoid the influences of the innervation zones. Secondly, it shows the analysis of the time-varying autoregressive (AR) parameters of EMG signals and the Karhunen-Loéve expansion of multidimensional EMG parameters, to identify the physiological factors that cannot be revealed by the muscle force.

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The purpose of this study was to answer the question of whether orthodontic treatment influenced chewing function. The chewing movements while chewing gum were recorded with a MKG and an NEC computer and were processed by an automatic masticatory movement analyzing software system before and after orthodontic treatment in 10 patients diagnosed as Angle Class I with crowding. Twenty subjects with functionally and morphologically normal occlusion were selected as a normal group. The following parameters in terms of the chewing path were considered: the opening distance, and the standard deviation (SD) /the opening distance (OD) values in lateral distances of opening and closing movements and in vertical distance. The data after treatment as compared with those before treatment showed: statistically significant (p<0.01) increments in opening distance, statistically significant (p<0.05) decrements of SD/OD values in lateral distance of opening movement and statistically significant (p<0.01) decrements of SD/OD values in vertical distance, resulting in changing toward the normal ranges of the normal group. The results of this study suggest that morphological correction due to orthodontic treatment significantly contributes to functional improvement of chewing movements in terms of chewing path.

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In order to find the effect of the size of the food on the masticatory movement a chewing gum that retained its size and consistency was selected as the test food and 10 normal subjects were asked to chew 1 piece (1G), 2 pieces (2G), 3 pieces (3G), and 4 pieces (4G) of chewing gum. Then the muscular activities of the masticatory muscles along with the velocity, rhythm, and path of the masticatory movement of the 10 cycles beginning in the fifth cycle of each chewing session were calculated and analyzed. The results were as follows.
1) The amount of opening and the masticatory width increased as the size of the food increased, and a statistically significant difference was found between each and every session for the amount of opening and between 1 G and 3G, and between 1G and 4G for the masticatory width.
2) The rhythm of the movement
The occluding time remained the same regardless of the size of the food. No significant difference was found between any session. The opening time, closing time, and cycle time increased slightly as the size of the food increased. Significant differences were found between 1 G and 4G and between 2G and 4G.
3) The velocity of the movement
The maximum velocity of opening and closing increased as the size of the food increased. Significant differences were found between 1G and the other sessions and between 2G and 4G for the maximum opening velocity, and between 1 G and other sessions for the maximum closing velocity.
4) The muscular activities
The cumulative value of masseter and temporal muscles increased as the size of the food increased. Significant differences were found between 1G and the other sessions for masseter muscle and between 1G and 3G, and between 1 G and 4G for temporal muscle.
5) From the above results it was clear that as the size of the food increased the quantitative indicators of masticatory movement, the path, rhythm and velocity, changed along with one or all of the indicators of the muscular activities. This could lead to the thought that the changes in the sensory input from the periphery has affected the masticatory movement.

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The aim of this research was to investigate the acoustic characteristics of clicking sound.
In this article, Peak Sound Pressure Level (PSPL) and Mean Power Frequency (MPF) were studied, and the relation of both parameters was investigated. The subjects were 6 patients with unilateral reciprocal clicking caused by anterior displacement of the disc with reduction. The results were as follows.
1. The mean values of PSPL ranged 78.2dB-103.2dB.
2. The mean values of MPF ranged 428Hz-758Hz.
3. According as PSPL increased, MPF shifted higher range in 4 of the 6 subjects.

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In this study, we measured jaw movement of female volunteers who did not exhibit any symptoms of temporomandibular joint dysfunction using a new jaw tracking device using two magnetic fields in quadrature phase.We compared the diagnostic parameters of females whith those of males which ware reported in a previous study.
Furthermore, we considered the characteristics of a new jaw tracking device.
1. The parameters which related to range of the border movement showed significant difference due to the physical proportions between males and females.
2. The parameters which related to excursive movements did not show significant difference between males and females.
3. The parameters which related to habitual mouth opening show significant difference due to the measurement error between males and females.We must improve the new jaw tracking device.

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It is known that occlusal interference is related to some systemic symptoms. However, there are few reports on the mechanisms of these systemic symptoms. In particular, the mechanisms for abnormality of the autonomic nervous system induced by occlusal interference still remain unclear. This study was designed to examine the influence of occlusal interference on the autonomic function and to clarify its mechanisms in 52 unanaesthetized rats. The blood pressure was measured as one of the autonomic functions, from the caudal artery by the tail-cuff method before, during and after insertion of bite-raising splints. The unilateral bite-raising splints (1, 2 or 3mm in vertical dimension) were set on the upper teeth to produce an occlusal interference to be sustained for 20 days. The blood pressure of the 1mm unilateral bite-raising group did not change significantly between before and during insertion of the splints. Unilateral bite-raising of 2mm and 3mm resulted in a significant increase of blood pressure. After removal of the splints, the blood pressure returned to the pre-insertion level. Unilateral bite-raising also produced a statistically significant reduction of the body weight during insertion period of the splints. However, when the effect of fasting on the blood pressure was examined, the blood pressure did not change significantly, whereas the body weight decreased remarkably during fasting. This result indicates that the increase of blood pressure depended primarily on unilateral bite-raising. Furthermore, α- and β-adrenergic antagonists, prazosin and propranolol, respectively, were used to determine the mechanisms of increase of blood pressure induced by occlusal interference. The increased blood pressure decreased significantly after the administration of prazosin. There was no statistically significant difference of heart rate between before and after administration of prazosin. Propranolol also significantly reduced the blood pressure, however, no statistically significant difference was observed in the heart rate. The result suggests that activation of the autonomic nervous system is involved in the increase of blood pressure induced by insertion of unilateral bite-raising splints, and that the increase of blood pressure induced by occlusal interference is mediated by activation of the sympathetic nervous system.

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The purpose of this study is to investigate the effect of occlusal condition upon the excitatory reflex response of the motor unit of the temporal muscle on the balancing side induced by the mechanical stimulation provided to the maxillary canine on the working side, in reference to the lateral movement from the working side to the intercuspal position in the final stage of jaw-closing phase during human masticatory movement.
6 subjects with canine in normal overjet and 2 subjects with cross-bite canine were chosen. Then, the responses of the temporal muscle induced by the mechanical stimulation provided to the maxillary canines on the working side in such different conditions were compared.
The mechanical stimulation, linguo-labially and labio-lingually directed pressure, was provided to the canines to stimulate the periodontal ligament and the range of the pressure applied was 100-800gf. The activity of the motor unit which spontaneously discharged were selectively delivered by needle electrode from the anterior part of the temporal muscle on the balancing side. While the canine was being stimulated, the mandibular position was kept to the lateral side approximately 2mm by using incisal point as reference point without occluding. This mandibular position measured by MKG was visually feedbacked by the subjects.
The results were as follows:
In the normal overjet, the excitatory response of the contralateral temporal muscle to linguo-labially directed pressure on the maxillary canine on the working side was observed. Although the similar tendency of the response to the labio-lingually directed pressure was observed, the response was less than that of to the linguo-labially directed pressure.
On the contrary, the cross-bite canine had different response pattern from the canines in normal overjet. The excitatory response to the labio-lingually directed pressure was observed, while there were no responses to the linguo-labially directed pressure. According to these obtained results, the temporal muscle showed the different responses, when the pressure of the same direction was provided to the tooth in the different occlusal condition. Hence, it suggested that the reflex response from the maxillary canine on the working side to the contralateral temporal muscle depended upon the occlusal condition of the canine, and the various response patterns of the temporal muscle possibly reflected the occlusal conditions.

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On the basis on a definition of mandibular supporting composite as an assembly of elastic, viscous and muscular contractile elements that concern mandibular positioning, in this study we tried to explore a possibility to evaluate muscular symptoms objectively by means of a kinetic evaluation of mandibular supporting composite in passive movement.
Two male subjects volunteered to be applied a sudden load on their mandible while they kept their rest position. Mandibular movement and electromyogram were simultaneously recorded during loading. Afterwards, subjects were requested to clench by their maximum voluntary force as long as possible for experimental task to induce fatigue-like feeling. The effect of task and fatigue-like feeling was also observed at immediately, 24 hours and 48 hours after the task.
It was noted that passive opening movement was observed quite similar at repeated registration in each subject. Opening speed at initial 20 (ms) decreased immediately after the task in every subject. From 24 hours after the task, the opening speed was restored in various ways. These results suggest that kinetic analysis of mandibular supporting composite in passive movement could be used to evaluate the muscular symptoms of patients with temporomandibular disorder objectively.

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