The purpose of this paper is to clarify the influence of splinting with bridge work on the movement of abutment teeth during function. Upper sencond premolar and second molar were splinted without any changes of occlusal tooth contacts and interdental proximal contact relations. The movement of these teeth were recorded on a horizontal plane at the same point before and after splinting.
Conclusions were as follow:
1. The movement of abutment teeth were changed by splinting. The direction of tooth movement did not always change into the median direction of both teeth movement, and sometimes only one tooth movement was changed under the influence of the other tooth movement.
2. The range of physiological tooth movement was limited in some degree to mesiodistal direction; therefore, splinting had the similar effect to interdental proximal contact relation.
3. Splinting with about three-unit-bridge did not give an influece on the periodontium of the abutment teeth.

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In this study, the author investigated changes in upright posture in 4 TMD patients while the mandibular position was altered for 1 and 5 minutes in a horizontal direction at the distances of 2.5 and 5.0mm.
Namely, loci of gravity fluctuation were examined under analysis system in order to reveal what effect was given upon the upright posture. At the same time, electromyograms were obtained from muscles of masticatory system, neck and lower extremity for the observation of effects on gravity muscles. The results obtained were as follows:
1. Loci of gravity fluctuation
1) Loci of gravity fluctuation tended to increase beyond the normal range when the mandibular position was hor-izontally changed for 1 and Sminutes at the distances of 2.5 and 5mm. Many patients had differences between right and left directions.
2) Changing amounts were less in the anterior direction than in the right and left directions.
2. Activities of antigravity muscles
Although muscular activities showed similar tendencies to those of loci of gravity fluctuation they showed indi-vidual differences.
3. Since these results revealed that horizontal changes in mandibular position influenced both loci of gravity fluc-tuation and muscular activities, it was suggested that changes in the stomatgnatic system are involved in the sys-temic condition, and that the the recovery of adequate function of the stomatognatic system is essential to the maintenance of systemic harmony.

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For complete denture wearers, the tongue plays an important role in the masticatory function. Furthermore good muscular coordination and control of the tongue are essential to complete denture retention and stability. But the relationship between tongue motor skill and masticatory performance is still not clear, because tongue motion is complicated and the evaluation of motor skill is difficult.
In this study an ultrasound system was used for the analysis of tongue motor skill. To elucidate relationship between tongue motor behaviour and masticatory function in complete denture wearers, 20 edentulous patients were tested, both their motor tongue skills and masticatory performance . Tongue motor skill was evaluated by the ultra-sound diagnostic system with motion-modulation images which was developed by our group.
For the evaluation of masticatory performance in complete denture wearers, masticatory performance was analyzed by two methods, masticatory efficiency by the sieving method using peanuts and“the chewing score”indicating the chewing ability by a food intake questionnaire method developed by our group.
Furthermore the age-related change of tongue motor skill and masticatory performance were discussed.
The results were as follows.
(1) The correlation coefficiency was 0.52 between age and the tongue motor skill in complete denture wearers which was statistically significant at a 0.01 level.
(2) The correlation coefficiency was -0.60 between age and masticatory efficiencies in complete denture wearers which was statistically significant at a 0.01 level.
(3) The correlation coefficiency was -0.46 between age and chewing score in complete denture wearers which was statistically significant at a 0.05 level.
(4) The correlation coefficiency was 0.83 between the masticatory efficiencies and chewing score in complete den-ture wearers which was statistically significant at a 0.01 level.
From these results, it is suggested that the masticatory function in complete denture wearers is influenced by tongue motor skill. It is also suggested that the masticatory function in complete denture wearers decrease in relation to aging. It is also confirmed that the food intake questionnaire method is useful for evaluating masticatory function in complete denture wearers.

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The purpose of this study was to investigate the relationship between masticatory muscles function and exercise of the whole body in sports.
Ten players in the volleyball team“JT”and ten players in the handball team“Wakunaga Pharmacy”volunteered as subjects for this project. Two kinds of spike (the most powerful spike with jump, slight spike without jump) in vol-leyball and two kinds of shoot (the most powerful shoot with jump, pass without jump) in handball were selected as the test exercise of the whole body. Electromyographic signals during spiking volleyballs or shooting handballs were recorded in subjects from both sides of M.Temporalis Anterior and M.Masseter, from the test side of M.Biceps Brachii, M. Triceps Brachii, and M. Flexor Carpi Ulnaris by means of surface electrodes and telemetry EMG device units. Furthermore, spiking or shooting forms were recorded by use of the video camera.
Following results were obtained;
1. Clear activity of four masticatory muscles during spiking volleyballs or shooting handballs was shown in all subjects.
2. There was a positive correlation between masticatory muscles activity during spiking volleyballs or shooting handballs (the duration and the ratio to maximum-clenching muscles activity) and the strength and form of spik-ing or shooting.
Those results suggest that the masticatory muscles may play a significant role in the exercise of the whole body in sports.

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In order to verify the functional differences in the masticatory movement between chewing hard chewing gum and chewing softened chewing gum the path and the rhythm of the 10 strokes of the movement beginning with the fifth stroke of the mastication of 10 healthy subjects chewing chewing gum were analyzed using our own system and the following results were obtained.
1) The amount of opening and the width of mastication were larger before the chewing gum softened and a statis-tically significant difference was found between chewing hard chewing gum and chewing softened chewing gum.
2) Each SD/OD of the lateral and vertical components of the opening time and the closing time was larger before the chewing gum softened, and a significant difference was found between chewing hard chewing gum and chewing softened chewing gum.
3) When the threshold value was set at lmm below centric occlusion, the average occluding time was shorter before the chewing gum softened. However, the average of opening time, closing time and cycle time were all longer before the chewing gum softened.
4) When the threshold value was set at 2mm below centric occlusion, the average occluding time was about the same for both hard and softened chewing gum, but the average opening time, closing time and cycle time were all longer before the chewing gum softened.
5) When the threshold value was set at 3mm below centric occlusion, the average occluding time, opening time, closing time, and cycle time were all longer before the chewing gum softened.
6) Each coefficient of variation of the cycle time when the threshold value was set at 1mm, 2mm, and 3 mm were all larger before the chewing gum softened, and a significant difference was observed between chewing hard chewing gum and chewing softened chewing gum.
7) From the above results, it was clear that before the chewing gum softened both the vertical and lateral move-ments were larger and the rhythm was unstable, and that a functional difference existed between chewing hard chewing gumand chewing softened chewing gum.

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In order to obtain a clear picture of bruxism during sleep at night in patients wearing complete upper and lower dentures using cuspless teeth, the biological phenomena during nocturnal sleep of 5 stable complete denture wearers were recorded by a wireless telemeter, and the frequency of masseter muscular activity was compared with the results of 7 normal subjects which has been published previously.
1. No significant difference was found between the normal subject group and the complete denture wearer group in the total amount of sleep.
2. The frequency of EMG burst of masseter muscle was lower for the complete denture wearer group than for the normal subject group, and a statistically significant difference was found between the two groups. And no significant difference was found between the habitual chewing side and the non-habitual chewing side of the complete denture wearer group.
3. The frequency of EMG burst group of masseter muscle was also lower for complete denture wearer group than for the normal subject group, and a statistically significant difference was found between the two groups. And again no significant difference was found between the habitual chewing side and the non-habitual chewing side of the complete denture wearer group.
4. The duration of the muscular activity was shorter for the complete denture wearer group than for the normal subject group, and a statistically significant difference was found between the two groups. And no significant difference was found between the habitual chewing side and the non-habitual chewing side of the complete denture wearer group.
5. From the above results it was suggested that for stable complete denture wearers the level of masseter muscular activity during sleep at night was much lower than that of normal subjects, and that the muscular activities were even for both the habitual and non-habitual chewing sides.

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In order to obtain a clear picture of the onset of sleep apnea in complete denture wearers, the biological phenomena during nocturnal sleep of 5 stable complete denture wearers, ages from 49 to 65, were recorded by a wireless telemeter, and the results were compared with that of 7 normal subjects, 7 bruxists, and 10 CMD patients which has been published previously.
The frequency of sleep apnea was high only for the bruxist group and a statistically significant difference was found only between the bruxist group and the normal subject group. For the average duration of sleep apnea no significant differences were found between each group. Also no significant differences were found between each group for the frequency of sleep apnea connected with masseter EMG burst group. On the other hand there was an increase in stage 2 and a decrease in stage 4 of the EEG sleep stages associated with sleep apnea, and this trend became more conspicuous in the order of nomal subject group, bruxist group, CMD patients group and the complete denture wearer group.
From these results it was suggested that the frequency of sleep apnea for the stable complete denture wearers was generally at a normal level. And for the report that the frequency of sleep apnea increased along with the age, the necessity of analyzing the possible effect of functional problems of the masticatory system along with the biological changes associated with aging was suggested.

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Authors have been engaged in developing a measuring device which measures the lower jaw movement with 6 free axes by magnetism. In order to examine the clinical performance of the device, the accuracy was evaluated through reproducing measuring conditions and various types of the lower jaw movement on an articulator and the following conclusions were obtained.
1. The maximum error in the distance with this device was 3.3mm in the incisal point when the maximum aperture movement from the centric occlusion was performed by a subject.
2. The maximum error in the angle with this device was 2.13°in sagittal plane when the maximum aperture movement from the centric occlusion was performed by a subject.
3. The prospect that this device can be used for measuring the lower jaw movement with 6 free axes at an actual clinical situation was obtained by this research.

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Roles of afferents from muscle spindles in jaw-closing muscles and infrahyoid muscles on the jaw position during opening and closing movements were studied in healthy human subjects. Vibration was applied to the tendon of those muscles to activate muscle spindles. Two series of experiments were performed. In the first series, the subjects performed slow jaw-opening and -closing movements (<l0mm/s) to an instructed end position without visual feedback. When vibration was applied to the tendon of the masseter muscle during opening-movements, all the subjects significantly overestimated the end position compared with the control (p<0.001) .When vibration was applied during closing movements, two of five subjects significantly overestimated the final end position (p<0.01), but the remaining three showed no difference from the control. Furthermore when vibration was applied to the tendon of masseter muscle during moderately fast jaw movements, eight of ten subjects significantly overestimated the final end position (p<0.05) . In the second series, vibration was applied to the tendon of the infrahyoid muscle during slow jaw movements to an instructed end position without visual feedback. When vibration was applied during closing movements, all the subjects significantly overestimated the final end positon (p<0.05) . It is suggested that the afferent information from the masseter muscle and infrahyoid muscle are mainly available to the jaw-opening and -closing movements, respectively.

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The purpose of this paper was to investigate the fundamental function of muscular sound in the masseter muscle. Muscular sounds produced during sustained voluntary contractions of the masseter muscle were recorded by accelerometer in five healthy adults. Simultaneously surface EMG, needle EMG and bite force were recorded during isometric contractions.
At the onset of the exercise, the amplitude of the sound signal increased and with time of exercise the amplitude rapidly diminished.
Integrated surface EMG amplitude increased linearly with bite force, but integrated muscular sound amplitude did not changed.
Mean power frequency of surface EMG and muscular sound did not changed with increasing bite force.
The range of frequency for muscular sound was estimated to be between 10 and 40Hz.
Muscular sound, surface EMG and bite force were studied by averaging technique, and it was revealed that mus-cular sound was the mechanical counterpart of the muscle action potentials.

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We examined the changes of masticatory function by chewing training using hard chewing gum (gum) .
Ten adult males were requested to chew hard gum for 10 minutes after each mealfor four weeks. EMG and mandibular movement during gum chewing and masticatory performance were recorded.
The burst duration and interval of EMG were significantly shotened by training. The burst duration of EMG did not recover pre-training level after the end of training for two weeks. Nuscle activity and masticatory performance were not influenced by training.
The maximal vertical, antero-posterior and lateral displacement of mandible
during gum chewing were not affected by training. The maximal opening and closing velocities tended to be increased bytraining. Closing, occlusal and openingphase and cycle time were significantly shortened by training.
These results suggested that the masti-catory muscle power was promptly produced and not increased by chewing training.

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An electrical stimulation of the superior alveolar nerve arising from the intraoral region elicited a large reflex discharge (trigemino-neck reflex: TNR) in the second cervical nerve to the dorsal neck muscles in the anesthetized cat. The TNR by the oral sensory inputs had a low threshold as well as the short- and long-latency TNRs by the facial sensory inputs. This finding indicates that the mechanoreceptors in the oral region could be involved in initiation of the TNR as well as those in the facial skin. With increasing stimulus intensity, the latency of the TNRs decreased, while both their amplitude and duration increased. Comparing the latencies under identical response magnitude, the TNR by the oral sensory inputs had a similar latency to the long-latency TNR by the sensory inputs from the upper lip. The result suggests that the sensory inputs from the oral and the lip could play a similar role in regulating the head and neck movement of cats. On the contrary, in the anesthetized rabbit, a very small TNR was found by the sensory inputs from the oral region as well as by those from the lip, although a large TNR was induced by the sensory inputs from the nose. There was no significant difference in the threshold value and the latency among these responses. The finding suggests that there exists only one response elicited by the sensory inputs from nose in the TNR of rabbits.

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The connection between osteointegrated implants and surrounding bone is direct. But the tissue surrounding natural teeth is composed of periodontal ligament. To determine the difference of viscoelastic properties between teeth and the implants, we measured the mechanical mobility of teeth and the implants using the automatic diagnostic system for tooth mobility we developed. We investigated a correlation between three mechanical parameters obtained and root/crown ratio of natural teeth and the implants.
The obtained results were as follows:
1. It is possible to evaluate the viscoelastic properties of the bone surrounding osteointegrated implants with the use of three parameters calculated from mechanical mobility measurement.
2. A correlation was found between a quantity of the surrounding tissue and the mechanical parameters for both of teeth and the implants.
3. The mechanical mobility of the implants was smaller than those of teeth, and the difference of the viscous parameter value was even more marked.

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The purpose of this study is to investigate the role of periodontal sensation in the regulation of human masticatory movement, particularly during lateral jaw movement from the working side to the intercuspal position. For this purpose, the responses of motor units of temporal muscle from 4 subjects to mechanical stimulation of the maxillary canine on the working side were analysed. To stimulate the periodontal ligament, the linguo-labially directed pressure was provided to the maxillary canine.The activities of the motor units which spontaneously discharged were delivered by needle electrode from anterior part of temporal muscle. While the canine was being stimulated, mandibular position was kept to the lateral side approximately 2mm by using incisal point as reference point. This mandibular position measured by MKG was visually feedbacked by the subjects.
The results were as follows:
The excitatory response of the contralateral temporal muscle to tonic mechanical stimulation of the maxillary canine on the working side was observed.The contralateral temporal muscle responded much more clearly than the ipsilateral temporal muscle did.
After the sensation of periodontal ligament was blocked by 2% Xylocaine apical infiltration and intraligamental injection, the contralateral temporal muscle gradually showed less response. Therefore, it was proven that the periodontal sensation induced this contralateral temporal muscle response.
During gum-chewing, the activity of these motor units was observed, particularly during lateral jaw movement from the working side to the intercuspal position. Therefore, it was proven that these motor units participated in masticatory movement.
From these obtained results, it suggested that periodontal sensation of the maxillary canine on the working side controlled the activity of the contralateral temporal muscle and took part in the regulation of the human masticatory movement pathway, particularly during lateral jaw movement from the working side to the intercuspal position.

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Occlusal curve is a morphologically important factor in the occlusion and is believed to influence the stomatognathic function, especially chewing movements. Excessive occlusal curves are found in some craniomandibular disorders (CMD) patients clinically. However, there have been a few studies about relationship between occlusal curve and stomatognathic function. The purpose of this study is to investigate occlusal curve of CMD patients and relationship between occlusal curve and chewing movements.
Forty healthy subjects and 95 patients with CMD (50 patients with anterior disk displacement with reduction (Click), 25 patients with anterior disk displacement without reduction (Lock) and 20 patients with myofascial pain dysfunction syndrome (MPDS) ) were examined. Their position of cusps was measured by three-dimensional measuring system and occlusal curve was estimated sagittally and laterally. The degree of mandibular sagittal occlusal curve (curve of Spee) was expressed by a second order coefficient of an approximate quadratic curve. Lateral occlusal curve was estimated by comparing the central points of Monson's sphere respectively calculated by the approximation in 4 kinds of cusps, mandibular buccal and lingual cusps and maxillary buccal and lingual cusps. Movements of the incisor point during chewing were recorded with Sirognathograph Analysing System. The parameters of chewing movements consisting of 68 items are divided into 10 categories according to the principal component analysis. The relationship between the degrees of occlusal curve and the principal component scores of 10 categories was analyzed by the multiple regression analysis.
The results were as follows;
1. Patients in Click group and Lock group had more excessive curve of Spee (p<0.05) and more excessive mandibular lateral occlusal curve (p<0.05) than healthy subjects. Additionaly, patients in the Lock group had flatter lateral occlusal curve in maxillary molars (p<0.05) than healthy subjects. Patients in the MPDS group had flatter lateral occlusal curve constituted by maxillary lingual cusps and mandibular buccal cusps (p<0.05) than healthy subjects.
2. Curve of Spee had relation to rhythm, regularity of path, stability of maximum speed of chewing movements and lateral form near and at the occluding point in opening phase of chewing movements. Lateral occlusal curve had relation to lateral and sagittal form of chewing movements near and at the occluding point in closing phase.
The results suggest that a close relationship exists between occlusal curve and stomatognathic function. Occlusal curve should be better estimated when the patients with CMD are examined.

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While reflexive mechanisms have been long known to be involved in the regulation of posture, there has been a tendency to regard all postural control as being implemented by feedback mechanisms. Whereas, when freestanding individuals raise one arm as rapidly as possible, anticipatory muscle activities are evoked in the leg segment prior to the initiation of electromyographic (EMG) activity of agonist. This finding indicates anticipatory activities of postural muscle are preprogramed in the brain, and reflect the function of positive postural adjustment rather than reorganization by postural reflexes.
The purpose of the present study was to investigate whether anticipatory postural muscle activitees could appear during jaw functional movements. Subjects were asked to respond with a ballistic jaw opening as rapid as possible to an acoustic stimulus signal. The EMG onset of sternocleidomastoid muscle (SCM) were compared with that of anterior digastric muscles (Da) . The SCM's onset tended to precede tha Da's. Relation between firing latencies of the SCM and reaction time (RT) were highly significant. These results suggested that the activity of SCM might be a component of voluntary ballistic jaw opening.

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As the dental arch form is the curve connecting the cusp tip of each tooth, it is one of the important factors of occlusal reconstruction. Many studies about dental arch form have been reported but it is unclear to infer the position of the teeth in dental arch form, and to evaluate the effect of the horizontal dental arch form on chewing movement. The purpose of this study is to elucidate the effect of dental arch form on chewing movement.
100 subjects with individual normal occlusion were evaluated. By multiple regression analysis on the basis of the relation of position of the canine and the first molar, the positions of teeth in dental arch were inferred. According to buccolingual relationship of maxillary to mandibular posterior teeth, the dental arch forms were classified into five groups.
Using Sirognathograph Analyzing System i, the patterns of chewing movement were analyzed by Maruyama's classification. According to the classification of dental arch form and the analysis of patterns of chewing movement, the patterns of chewing movement in each group were evaluated and compared with those of the normal group.
Results were summarized as follows;
1.Objective criteria to infer the positions of the first premolar, the second premolar, and the second molar in dental arch were established.
2. Opening path in chewing movement
The group in which the maxillary second molar's position is on the buccal side, the chewing patterns which have the vertical guide openings in frontal plane, the posterior guide openings in horizontal plane were observed.
The group in which the maxillary premolar's position is on the lingual side, the chewing patterns which have the protrusive shift openings in horizontal plane and sagittal plane were observed.
3. Closing path in chewing movement
In each group except for the normal group, the chewing patterns which have the concave closings in frontal plane and in horizontal plane were observed.
The group in which the maxillary premolar's position is on the buccal side, the chewing patterns which have the lateral guide closings in frontal plane and in horizontal plane, the vertical guide closing in sagittal plane were observed.
From the results, the close relationships were found between dental arch form and chewing movement. It is suggested that the evaluation of dental arch form is effective in the diagnosis of function of stomatognathic system.

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By analyzing the degree of jaw opening from the magnetic resonance imaging (MRI) and measuring the deflection point of the condylar path, confirmation involving the relationship between the two in connection to the condition of the temporomandibular joint (TMJ) was possible. This noninvasive technique was particularly helpful in evaluating the condition of the disc to the condyle.
Methods included analyses from the MRI and mandibular movements obtained from two male and one female patients having unilateral reciprocal clicking. The MRI was obtained by using a 1.5 T superconducting MR scanner equipped with bilateral surface coils. For MRI scanning the patients were asked to open and close their jaw divided into 11-15 phases depending upon their jaw opening ranges. To find the opening ranges at which the disc captured and slipped over, increments or decrements between the phases were set at 5 or 6 mm with the help of a nonmagnetic jaw positioning holder. Bilateral MRIs were obtained simultaneously, recorded at a time span of as short as 16 s in MPGR gradient echo pulse sequence for each slice to be edited at cine-MRI. The mandibular movement was measured by a six degree of freedom jaw tracking device, and the incisal point and both sides of the condylar point were used to analyze the mandibular movement during jaw open-close movement.
Combining MRI findings together with the condylar movement analysis, confirmation of the relationship between the disc positional change and clicking was obtainable. It was also found that the degree of the disc displacement could affect the condylar movement, and that this method could aid in clarifying the mechanism involved in jaw clicking.

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The purpose of this study was to investigate the relationship between masticatory muscles function and exercise of the whole body in sports.
Six players in the soccer team“Sanfrecce Hiroshima”volunteered as subjects for this project. Three kinds of kicking (the most powerful shoot, the longest pass, slight shoot) were selected as the test exercise of the whole body. Electromyographic signals during kicking were recorded in subjects from both sides of M. Temporalis Anterior and M. Masseter, from M. Gastrocnemius and both sides of M. Quadriceps Femoris by means of surface electrodes and telemetry EMG device units. Furthermore, kicking forms were recorded by use of the video camera.
Following results were obtained;
1. Clear activity of four masticatory muscles during kicking was shown in two subjects.
2. There was a positive correlation between masticatory muscles activity during kicking (the duration and the ratio to maximum-clenching muscles activity) and the strength and form of kickings.
Those results suggest that the masticatory muscles might play a role in kicking and the exercise of the whole body in sports.

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When surface electromyography of masticatory and neck muscles of Cranio-Mandibular-Disorders (C.M.D.) patients is carried out, a continuous spontaneous discharge with a wave pattern showing a rather small and constant amplitude may often be observed just after clenching or just before/after chewing.
In the past there have been reports that stated that this spontaneous discharge was closely related to the hyperactivity of the muscles and disappeared after occlusal therapy.
We believe that this spontaneous discharge is closely related to the symptoms of C.M.D.. Therefore we hypothesize that its incidence is related to the degree of the symptoms of C.M.D.. If this hypothesis is true, when we perform on patients a prescribed examination, the incidence of such discharge in a prescribed time is suitable for the parameters of evaluation of the degree of the symptoms of C.M.D..
For calculating the incidence of the spontaneous discharge, it is a priority to obtain the occurrence time of it. Up to now, by the conventional method, the examiner has to distinguish subjectively between the spontaneous discharge and the discharge by voluntary contraction. A new analysis has been developed that will distinguish objectively and calculate effectively the incidence of the discharge of the muscles. This analysis, called the Amplitude Distribution Analysis, is a computer program that analyses the distribution density of voltage for all the digitalized data of some signals.
In this article we explain this analysis and how we analyzed three kinds of standard signals (a square wave, a chopping wave and a sine wave) by using an oscillator.
We analyzed two kinds of muscle discharges, the normal discharge during M.V.C. in subjects without signs of C.M.D., spontaneous discharge in C.M.D. patients.
The results yielded by our experiment are inspiring since the amplitude distribution analysis enabled us to:
1) Identify the differences of such wave forms.
2) Analyze between the normal discharge during Maximum Voluntary Clenching (M.V.C.) in normal subjects with good occlusal relations and are free of C.M.D, symptoms, and the spontaneous discharge that occurs immediately after M.V.C. in C.M.D. patients.
3) Evaluate the results of analyzing by half band width of this chart, half band width/peak to peak amplitude. We think that the Amplitude Distribution Analysis enables us to recognize the difference in wave forms. We anticipate it is useful for the diagnosis of C.M.D. patients.

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Mastication is rhythmical movements that co-activate with masticatory muscles, cephalic-cervical muscles, lingual muscles and soft tissues of the mouth. Some authors reported simultaneous EMG activities of masticatory muscles, sternocleidomastoid muscles and lingual muscles during mandibular movements. It is estimated from these neuromuscular co-activations with mandibular movements that the head will also move rhythmically. But there are no reports available about it.
The purpose of this study was to elucidate the co-operative head movement during mastication according to the method of measuring maxillary and mandibular incisal points at the same time. Results:
1) The maxillary incisal point moved cyclically in progress of mastication.
2) The movements of the maxillary incisal point during one chewing cycle projected on the frontal plane showed closed circuits like those of the mandibular incisal point movements.
3) The maxillary incisal point moved in direction of the non-chewing side 0.2 seconds before the end of the chewing cycles.
4) The maxillary incisal point moved in upper direction at jaw opening period, and moved in lower direction at jaw closing period but hardly moved in horizontal direction during tapping.
Therefore these observed maxillary incisal point movements can be considered as co-operative head movements during mastication.

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Clinical application of a leaf gauge which can be used to locate the deviated mandible in centric relation are reported. However, a rationale for the treatment of abnormal muscles activities by the use of the leaf gauge is still unclear.
The aim of this study was to investigate a rationale for the physiological effects based on the biomechanical factors of deprogramming of abnormal masticatory muscle activity after created abnormalities due to experimental occlusal interference.
The detail method is following our former reports (Mushimoto et al, Yaegashi, 1994) . Six volunteer student were selected as subjects with normal occlusion without any symptomatic CMD. Subsequent recorded EMGs from bilateral masseter, anterior and posterior temporal muscles during brief maximal clench before and after insertion of a leaf gauge were analyzed. At the same time, Condylar Position Index applying X-ray Shuller and propotional ratio elongation of the masticatory muscles during insertion of the leaf gauge either 4mm or 16mm thick were also analyzed.
It was found that the reduced muscles activities were recovered by application of a leaf gauge, condylar position translated to anteriously and the masticatory muscles were elongated during the insertion of a leaf gauge.
In conclusion, it might be assumed that the positive feedback via the higher central from the elongated masticatory muscles activate the inhibited masticatory muscles.

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The purpose of this study was to establish the functional diagnostic parameters of the temporomandibular joint in both dentulous and edentulous patients, by comparing the threedimensional mandibular movement of the lower incisal point to the condylar movement and articular disc movement using simultaneous pseudodynamic MR imaging of the temporomandibular joint. In addition, the quantitative evaluation method of the mandibular movement was employed.
As a result, these methods were useful in understanding the three characteristic movements of the TMJ. These include the coordination of the bilateral condylar movement, the coordination of the condylar and articular disc movement, and finally, in the case of reduction of the anteriorly-displaced articular disc.
Of particular note, according to analysis from the view point of the coronal plane, was a tendency toward lateral deviation of the lower incisal mandibular movement. This deviation was related to the lack of coordination of movement between the bilateral articular disc and the condylar, which is so characteristic of CMD patients.
Prior to this research, functional diagnosis of the temporomandibular joint movement in edentulous patients had been difficult. This method may thus prove to be a first step in effective analysis of such conditions.

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To elucidate the interrelationship between the occlusal function and the bodily motor function, the clenching force, the masticatory muscle activity, the elbow flexion strength and the biceps muscle of arm activity during the maximum voluntary elbow flexion exercise were recorded and analyzed at horizontally different mandibular positions. Twelve normal dentate males (23-24 years) who realized the teeth clenching during a maximum voluntary efforts in physical exercise were selected as the subjects. The clenching force was measured by the sensor made with the pressure sensitive conductive silicone rubber sheet. This sensor was 20 mm square rubber sheet sandwiched by the copper foil contact plate for electrode and covered by polyimide resin for electrical insulation. In this total sensor, coefficient of variation was 1.67 % in 5 repeated measurements of output voltage. The correlation coefficient between the load and output voltage was 0.99. Measuring system of the clenching force was constructed by this sensor on the mandibular metal plate with a thickness of 2.0 mm and the central bearing point on the palatal metal plate.
The results obtained are as follows.
1) All the subjects were divided into two groups by the clenching force manifested during elbow flexion exer cise, namely, the hard clenching group (58.9-85.3 kgf) and the soft clenching group (4.9-13.2 kgf) .
2) In the hard clenching group, the maximum clenching force and the minimum standard deviation were demonstrated at the tapping point of mandible.
3) The maximum elbow flexion strength was demonstrated at the tapping point in both groups.
4) In the hard clenching group, the positive correlation coefficient between the clenching force and the elbow flexion strength was statistically significant (r=0.69, p<0.01) . On the other hand, there was no statistically significant result in the soft clenching group (r=0.04, p>0.05) .
In this study, the occlusal function is suggested to be closely interrelated with the bodily motor function.

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Among three major symptoms of TMD, clinicians have been considering joint sound as a possible indicator for the joint status. However, except subjective expressions such as clicking and crepitation, no objective method for evaluating joint sound have been established. The aim of this study is to evaluate joint sounds from both normal joints and joints with internal derangements and/or degenerative joint diseases.
Using arthrography and MR imaging, 83 normal joints and 214 abnormal joints were selected from the patients. Surface joint vibrations were recorded with a pair of piezoelectric transducers and the power spectrum density functions were calculated between 0 and 600 Hz.
Joints with meniscal displacement with reduction showed higher energy than the normal joints throughout the evaluated frequency range. The timing of reduction did not affect the frequency spectrum. Joints with meniscal displacement without reduction showed higher energy than the normal joints at the low frequency ranges between 0 and 150 Hz. Joints with perforations or degenerative changes showed higher energy than the normal joints throughout the evaluated frequency range. Joint with degenerative changes showed higher energy than joints with perforation at the high frequency ranges above 400 Hz.

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