Posterior Temporalis Research Articles

犬歯尖頭位の接触要素と最大かみしめ時の筋活動との関連性に関する研究

The purpose of this study was to clarify the normal relationships between anterior components of lateral occlusion and muscle activity of 12 healthy subjects. The location (LO) and area (AO) of occlusal contacts were measured by black silicone methods, frontal (FA) and horizontal (HA) angles were also measured by LED jaw tracking device at canine's edge to edge to lateral position (ED-LP) as an anterior component of lateral occlusion. Muscle activity of masseter muscle (Mm), anterior temporal muscle (Ta), posterior temporal muscle (Tp) were recorded bilaterally by bipolar electrodes during maximal voluntary clenching (MVC) at ED-LP.The muscle activity during MVC was affected by anterior components, and the most effective muscle was the working-side Ta and Tp. In the case that frontal teeth with canine restricted on working-side LO, the reduction of muscle activity was observed as the reduction of AO or increase of FA. However, if the molar teeth were included on working-side LO, AO did not affect the muscle activity which could be decreased only by the increase of FA. If the working-side contacts were established, the balancing-side contacts did not affect the muscle activity of Mm, Ta, and Tp during MVC.

三次元こう合力に基づく下顎位とそしゃく筋活動の関係に関する研究

The purpose of this study was to examine the relationship between jaw position and masticatory muscle activities during static bite situation. The subjects were 4 males and 1female. EMG activities were registered bilaterally from the masseter muscle (MAS), anterior temporal muscle (AT) and posterior temporal muscle (PT) in different jaw positions anteroposteriorly. During EMG registration, bite force was regulated both in magnitude and direction with visual biofeedback by means of a three-dimensional bite force measuring device. The relative activation pattern of the muscles during bites in specific directions was consistent irrespective of jaw position. During bites in a specific direction at a determined force, MAS activity increased as the jaw position was changed anteriorly, while AT and PT activities increased as the position was changed posteriorly. The difference between activities generated in different directions was dependent on jaw position in AT and PT, but not in MAS. The difference between the activities generated at different bite forces was dependent on jaw position in MAS and AT, but not in PT. It was suggested that these characteristics of muscle activity as changes of jaw position might be closely related to the shape and spacial location of muscles.

習慣性ならびに非習慣性そしゃく側におけるガムチューイング時の正規化筋電図包絡線による解析

The purpose of this study was to investigate the differences in coordination patterns of elevator muscles during gum chewing on the preferred and nonpreferred sides (PRC and NPRC) using normalized electromyographic linear envelopes (EMG LEs). Experimental tasks were carried out utilizing two kinds of gum with different hardnesses and ten normal subjects. EMG LEs normalized with respect to EMG amplitude and stroke were generated from surface EMG signals of bilateral anterior temporal, posterior temporal and masseter muscles (WTa, NWTa, WTp, NWTp, WM and NWM) and incisal point movement of the mandible. Differences in coordination patterns of EMG LEs for masticatory muscles between PRC and NPRC on different gum hardnesses were evaluated by the cluster analysis.On the soft gum, there was a high phasic similarity between EMG LEs of WM and NWTa during NPRC. NWM had similar phasic characteristics for another muscle during NPRC. On the hard gum, differences in muscle coordination patterns between PRC and NPRC were basically the same as those for soft gum chewing. From the viewpoint of chewing difficulty, there was no change in coordination patterns among WTp, NWTp and NWM between soft and hard gum on PRC in comparison with that between PRC and NPRC on soft gum.

下顎無歯顎にＢｒａｎｅｍａｒｋ ｉｍｐｌａｎｔを用いた６年経過症例の筋電図的評価

The masticatory function and the adaptation of patient's denture with Brånemark implant in the edentulous mandible was evaluated by using electromyography for 6 years. Electromyograms (EMG) of the bilateral posterior temporal and masseter muscles during gum chewing were recorded at insertion of the old full denture and at 1 month, 3 months, 6 months, 2 years and 6 years after insertion of implant denture. The interval, the duration and their integrated values of EMG bursts were measured.The duration of EMG burst was shorter with the implant denture than with the old full denture and became about 300 msec from 3 months after insertion of the implant denture. The coefficient of variance (CV) of duration became stable from 3 or 6 months after insertion of the implant denture.The EMG power coordination pattern was converted into a normal one representing the prominence of the working side masseter followed by the other three muscles after insertion of the implant denture.The periotest values of the implant fixture were not significantly changed after insertion of the implant denture, and osseointegration has been maintained.These results suggested that adaptation to the implant denture might require a longer period than that to the conventional denture.

Functional characteristics of retrognathic patients before and after mandibular advancement surgery

Purpose: The purpose of this investigation was to compare morphologic parameters and functional performance between controls and a sample of patients with mandibular retrognathia prior to surgical correction, and to examine how oral motor function adapts after treatment. Patients and Methods: Twenty-four retrognathic female patients were compared with 26 female controls before and up to 3 years after mandibular advancement surgery. Measures of skeletal morphology, mandibular range of motion, maximum isometric bite force, and levels of electromyographic activity in the anterior and posterior temporalis and masseter muscles during isometric bites were made on all subjects over time. One-way analysis of variance was used to compare the controls, the patients before surgery, and the patients after surgery. Results: Surgical lengthening of the mandible averaged 7.3 mm, bringing most skeletal measures into the normal range. There were no significant differences in jaw muscle mechanical advantage between patients and controls before surgery, but surgery significantly reduced mechanical advantage of the anterior temporalis and masseter muscles. Jaw hypomobility was apparent at 6 weeks after surgery, but returned to normal values within 12 to 24 months. Before surgery the patients had maximum isometric bite forces less than half those of controls. Bite forces steadily increased after surgery, approaching normal values within 2 years. Before surgery the patients' muscle activity levels per unit of bite force were equivalent to those of controls or somewhat higher. After surgery some of the patients' muscles had significantly lower levels of muscle activity per unit of bite force than did controls. Conclusion: The results of this study suggest that correction of mandibular retrognathia by mandibular advancement surgery produces some significant functional benefits.

The effects of orthodontic treatment on isometric bite forces and mandibular motion in patients before orthognathic surgery

Purpose: Little is known about the effects of orthodontic treatment on oral motor function. The objective of this report is to evaluate changes in mandibular motion and maximum bite force that occur between the initiation of presurgical orthodontics and its completion before surgery. Patients and Methods: Fifteen patients (9 women, 6 men) with a variety of dentofacial deformities were examined before and after presurgical orthodontics. Mechanical advantage of the muscles and bite points, mandibular range of motion, maximum isometric bite force, and levels of electromyographic (EMG) activity in the anterior and posterior temporalis and masseter muscles during isometric bites were recorded on all subjects over time. Data obtained before and after completion of presurgical orthodontics were statistically compared. Results: Presurgical orthodontics reduced mandibular mobility somewhat, but the amount was not significant. Statistically significant reductions in bite force were noted after orthodontics for incisor, canine, premolar, and molar bite positions. No significant difference in the EMG/bite force slopes was obtained, nor was there any difference in the moment arms of the bite points or the muscles of mastication from orthodontics. Conclusions: This study showed significant changes in measures of oral motor function resulting from orthodontic treatment. A larger study is needed to confirm that these results will be similar in all orthodontic patients. There is no indication that these changes are the result of physiologic alterations of the muscles of mastication. The best current explanation is that these changes result from the pain and discomfort of the orthodontic appliances and the induced malocclusion.

側方こう合位の歯牙接触要素と筋活動との関連性に関する研究 第２報 筋活動について

Electromyographic (EMG) activity was measured in the masseter muscle (Mm), anterior temporalis (Ta) and posterior temporalis muscle (Tp) during maximal voluntary clenching (MVC) and recording occlusal contacts by black silicon method (RBS) on 12 normal subjects with sound dentitions. Intercuspal position (IP), lateral position which was horizontally apart 1 mm from IP (LP-1) and canine's edge to edge lateral position (LP-E) were fabricated using LED mandibular tracking device; MVC was performed at IP and LP-E on all subjects; and RBS was at IP, LP-1 and LP-E on 9 subjects.Total muscle activity during RBS was about 10% of that during MVC at both IP and LP, but individual variation of EMG pattern exists. Ta and Tp showed significantly greater activity on the working side than the balancing side, while Mm showed no clear difference between the sides during both MVC and RBS at LP. The working side Ta showed significantly less activity during RBS than MVC at LP and was greatly affected by the clenching level, but while the balancing side Tp remained unchanged, activity was hardly affected.

The effects of food consistency on jaw movement and posterior temporalis and inferior orbicularis oris muscle activities during chewing in children

The possible effects of food consistency on the number of chews and the lapse of time in a chewing sequence, the jaw-movement pattern and velocity, and jaw and lip muscle activity during chewing were investigated. Fifteen healthy children with good occlusion were selected. First, each subject freely chewed hard (HJ) and soft (SJ) types of jelly without specifying the chewing side. The number of chews and elapsed time in a masticatory sequence (from the start of chewing to the completion of the final swallow) were measured. Second, the subjects performed right- and left-sided chewing of the same food. The electromyograms (EMG) of posterior temporalis (PT) and inferior orbicularis oris (OI) muscles on the right and left sides and associated jaw movement records were sampled. The HJ was chewed more times and with a longer time until finally swallowed ( p ⩽ 0.0007) than the SJ. The HJ chewing also showed broader masticatory loops ( p ⩽ 0.0199) in the frontal view and higher peak activities ( p ⩽ 0.0007) for the PT muscle. The closing phase was longer when chewing the HJ than SJ, but the opening and intercuspal phases remained stable. More lateral excursion of the jaw was seen when chewing the HJ, but the jaw-movement trajectories in the sagittal and vertical directions were not affected by the change in consistency of the food. The jaw-closing velocities for the HJ chews were significantly slower ( p ⩽ 0.0351) than those for the SJ chews in three directions. The HJ chews also revealed a longer duration between the onset of EMG burst for the PT muscle and the beginning of the centric occlusion ( p ⩽ 0.0146). The OI muscle showed increased activity in accord with jaw opening, and consistent reciprocal cyclic activity with the PT muscle in terms of temporal associations ( r ⩾ 0.5250; p ⩽ 0.0495). The OI muscle started to burst at a later part of the intercuspal phase, and frequently showed secondary activity in the jaw-closing and intercuspal phases. The peak activity for the ipsilateral OI muscle was significantly higher ( p ⩽ 0.0106) than that for the contralateral OI muscle for both the HJ and SJ. The OI muscle activity, however, did not differ between the hard and soft jellies. Thus the number of chews and the time elapsed from the start of chewing until the completion of the final swallowing of food in a chewing sequence increased when chewing a harder food. Also, the PT and OI muscle activity and associated jaw-movement patterns appear to be centrally regulated but peripheral information on food consistency might also modify the motor output to the PT muscle. The consistency of food, however, might not be influential in modulating the basic form of perioral motility during chewing.

The relationship between jaw-muscle mechanical advantage and activity levels during isometric bites in humans

Mathematical analyses of mandibular biomechanics often assume a close relation between the relative activity levels of the jaw-adductor muscles and their mechanical advantage. However, this relation has not been clearly demonstrated. This study examined the relation between muscle activity levels, force generation, and mechanical advantage in 48 (23 male, 25 female) normal subjects. Mechanical advantage in the sagittal plane was calculated from standard lateral cephalograms. Activity for the anterior and posterior temporalis and masseter muscles was recorded from surface electrodes during incisor and molar bites. Muscle activity was standardized by calculating a least-squares regression for electromyographic versus occlusal force. At each bite position the more efficient muscles were recruited at higher rates but muscle size was more important in determining efficiency than was mechanical advantage. Differences in jaw-muscle recruitment rates between males and females were also best explained by differences in muscle size. Decreased muscle recruitment rates at molar bite positions matched increased mechanical advantage for the anterior temporalis and masseter. However, posterior temporalis recruitment patterns seemed to reflect jaw position more closely than mechanical advantage.

Masticatory performance, muscle activity, and occlusal force in preorthognathic surgery patients

Previous studies have indicated that patients scheduled for orthognathic surgery tend to have lower maximum bite forces and exert lower forces during mastication. The effect of these deficits on masticatory performance have not been previously assessed. Masticatory performance was analyzed in four groups: male and female orthognathic surgery patients prior to presurgical orthodontics (n = 12 and 23), and male and female controls (n = 27 and 31). Mastication performance was analyzed by having the subjects chew 5-g pieces of carrot for 20 cycles and measuring the resulting median particle size with a standard sieve method. Masticatory performance showed the same trends as maximum bite force and masticatory forces: male controls had the best and patients the poorest masticatory performance. There was a weak correlation between masticatory performance and maximum bite force at the molar positions. Masticatory performance also weakly correlated to electromyographic signals during mastication of a constant bolus (gummy bears) for all muscles except the left posterior temporalis. Correlations were generally not present or were very weak between masticatory performance, estimated masticatory forces, and muscle efficiency, suggesting that muscle efficiency and forces generated during mastication are not the primary factors that determine masticatory performance. Other factors contributing to a person's ability to chew food might include occlusal relationships and mechanical advantage.

Estimated masticatory forces in patients before orthognathic surgery

There has been relatively little study of masticatory forces in dentofacial deformity patients before orthognathic surgery. This study used a mathematical equation based on electromyographic activity (EMG) during mastication and forces obtained during isometric bites to estimate masticatory forces in 55 control subjects and 48 patients. Subjects chewed on a constant bolus while EMG recordings were made bilaterally from the superficial masseter, anterior temporalis, and posterior temporalis muscles. Unilateral isometric bite forces in the first molar position and simultaneous EMGs were recorded in these same subjects. Superficial masseter muscle activity and isometric bite forces were strongly correlated. The slope of masseter EMG versus isometric force was used to estimate the masticatory forces. Males were found to have significantly higher estimated masticatory forces than females.

骨格性下顎前突症患者のそしゃく筋に関する筋電図学的ならびに組織化学的検討

This study was designed to identify differences in the masticatory muscles between patients with mandibular prognathism and normal subjects. Electromyograms during maximum centric occlusion and in the occlusion adjusted to 5 kg by the use of a jaw force meter (NIHON KOHDEN Co.) were recorded at the masticatory muscles (masseter, anterior and posterior temporal muscles) by means of surface electrodes. The occlusal force and total contact area during maximum occlusion were recorded and calculated using an Occlusal Prescale System (Fuji Film Co.). Thirteen patients with mandibular prognathism and 20 subjects without craniomandibular dysfunction were studied in terms of their electromyographic signals and occlusal force before and after orthognatic surgery. Histochemical analysis of the masseter muscles was carried out in 9 patients and 4 normal subjects.The results were as follows:1) The masseter muscles are the main muscles during masticatory movement in subjects without biting malfunction. The anterior temporal and posterior temporal muscles change their activity according to the working side and the balancing side.2) It was found that patients had higher electromyographic activity than subjects without malfunction in a closed-jaw position before surgery.The total-contact-area and occlusal force were significantly lower in patients compared with the normal group. There was no difference in average biting pressure.3) After orthognathic surgery, total-contact-area of centric occlusion and occlusal force were increased. There were no significant differences between patients and subjects without malfunction. There were also no significant differences in average biting pressure between the two groups both before and after surgery.4) There was a period of electric-overdischarge among the patients for 2 or 3 months after operation. Concurrently, a change in load ratio among the muscles was noted.5) A so-called “type 1 fiber predominance” masseter in which type 1 fibers accounted for over 55% of muscle fibers was found frequently in the patients. In some cases, electric-myographic volume was still high even after operation. This was found particularly among patients with a high-Type 1 fiber-ratio.

Effects of occlusal position on masticatory muscle activity

The effects of different occlusal position on the masticatory muscle function were investigated on 5 subjects. Two types of maxillary stabilization splints were fabricated in order to change the occlusal position. One type of the splints was to increase the occlusal height and the other was to shift the occlusal position laterally. The EMG activities of the masseter (M) and the anterior and posterior temporal muscles (AT, PT) were measured in various occlusal positions at 50% of maximal voluntary activity of the M and AT. The results were as follows: 1. When the occlusal height was increased. 1) The activity of the PT decreased in most subjects. 2) Asymmetry index (AI) of each tested muscle did not always indicate a similar value. 2. When the occlusal position was shifted laterally, 1) The activities of the ipsilateral AT and PT were higher than those of the contralateral side. 2) The AI of the AT and the PT changed gradually when the occlusal height was large while they changed greatly near the intercuspal position (IP) when the occlusal height was smaller. Therefore, the symmetry of the temporal muscle activity was thought to be influenced sensitively by the lateral shift of jaw position near the IP.

Ｌｅａｆ ｇａｕｇｅ法応用の効果発現のメカニズムに関する筋電図学的研究

A leaf gauge is a device that can be used to correct the mandibular position. However, a rationale for the treatment of abnormal muscle activities by the use of the leaf gauge is unclear.The aim of this study was to investigate a rationale for the physiological effect of deprogramming of abnormal jaw masticatory muscle activity after creation of this abnormal activity by the use of experimental occlusal interference during brief maximum clenching in the intercuspal position.Six normally dentate dental students were selected as the subjects. Surface electromyograms from the bilateral masseter, bilateral anterior and posterior temporalis muscles were used.In addition, two other aspects, occlusal surface contact and mandibular position deviation during brief maximum clenching, were studied.Four eleven-session experiments were carried out for a period of 14 days each. The sessions included before and after application of an occlusal interference, the interference period and removal of the interference, and subsequent observation of interference effects was carried out.The leaf gauge was used during each session with four distinct conditions, which were two leaf gauge thicknesses of 4 mm and 16 mm for each experiment and application of eachleaf gauge for 15 and 10-minute periods.It was found that separation of posterior teeth occurred one or two days after interference, the application of a leaf gauge in an attempt to correct the imposed abnormality of muscle balance. In addition, it was found that the mandibular position was repositioned the horizontally. The occlusal contact point surface has become larger in order to become normal.Two factors contributing to the reprogramming of muscle activities were found to be the thickness of the leaf gauge and the length of time of application.

バイオフィードバックを用いたこう合治療による顎関節症の治癒経過

The aim of this study was to elucidate the curing pattern of the clinical signs/symptoms in craniomandibular disorders (CMD) throughout the treatment period. 291 patients, who used CMD in this study, were completely relieved of their signs/symptoms at the end of the treatment process. The treatment process included occlusal adjustments, occlusal splint therapy and treatment dentures diagnosed with the use of biofeedback occlusal analysis.The patients were treated at 2-week intervals and the symptoms were examined and recorded. The average treatment times needed for complete cure of CMD was 7.00±5.02. The treatment period for each sign/symptom was calculated based on the total number of treatments for each patient. These were then compared and ranked statistically. First, the sequence of the signs/symptoms relieved were as follows. Tenderness on trapezius, posterior temporal, and occipital muscle disappeared significantly (p<0.01, t-test), and second spontaneous pain, chewing pain, and tenderness on anterior temporal muscle. Tenderness on lateral pterygoid, deep masseter, sternocleidmastoid muscle, TMJ, medial pterygoid, and superficial masseter muscle disappeared in this order. Then opening pain, TMJ noise and tenderness of posterior digastric were relieved (p<0.05). Lastly limited opening was relieved later (p<0.05) than all other symptoms. These findings clearly indicate that the cure of clinical signs/symptoms of CMD in the process of occlusal treatment would definitely have a pattern.

Effect of jaw opening on masticatory muscle EMG-force characteristics.

This study was designed to evaluate the way in which changes in vertical jaw opening affected the relative contributions of various masticatory muscles to bite force production. EMG activity was recorded simultaneously from the masseter, and anterior, middle, and posterior temporalis muscles, during controlled isometric biting at different force levels and vertical jaw openings. EMG-force characteristics were compared between muscles and bite openings. All but the posterior temporalis muscle displayed significant increases in muscle activity with increased bite force production; the masseter muscle demonstrated the largest activity increments. Statistically significant changes in muscle function due to jaw opening were demonstrated only for the masseter muscle, though similar trends were observed for the anterior and middle temporalis muscles. Minimum increases in muscle activity associated with increases in bite force occurred between 9 and 11 mm of opening, measured at the first molar, for all three muscle groups. The results of this study suggest that changes in masticatory muscle length resulting from vertical jaw opening cause alterations in muscle contractile properties, but the relative contributions of various masticatory muscles toward bite force production may also be affected by biomechanical factors and neural control adaptations.

A preliminary study of maximum voluntary bite force and jaw muscle efficiency in pre-orthognathic surgery patients

The functional state of dentofacial deformity patients before orthognathic surgery has received relatively little study. In this study, the ability to generate occlusal force was compared between 84 patients before treatment for various dentofacial deformities and 57 controls. Maximal and submaximal bite forces were measured at the incisor and right and left first molar bite positions. Electromyographic activity (EMG) was recorded bilaterally from the anterior temporalis, posterior temporalis, and masseter muscles during each bite. An efficiency ratio was calculated for the jaw muscles by dividing the level of EMG by the occlusal force. There was a reduced ability to generate occlusal forces in the patients before surgery, especially among female patients. The reductions in maximal occlusal force were correlated with reduced efficiency of the jaw muscles.

Occlusal control of mandibular elevator muscles.

Occlusal stability and mandibular elevator muscle function was studied in 25 women (20-30 yr of age). They had 27-32 fully erupted teeth with few treated occlusal surfaces, and craniomandibular function including mandibular mobility was normal. The aim was to analyze the influence of natural patterns of occlusal contact on electromyographic activity, unaffected by pain and functional disorders. Occlusal stability was assessed in the intercuspal and in lateral contact positions as the number of teeth with physical contact and the number of opposing pairs of teeth in contact. Electromyographic activity was recorded by surface electrodes over anterior and posterior temporalis and masseter muscles. In general, positive correlations were found between occlusal stability in intercuspal position and moderate to strong static and dynamic contractions, most significant in masseter muscles, indicating that forceful contraction of these muscles implies stable occlusion. Systematically, the duration of activity during chewing was negatively correlated with occlusal stability in the intercuspal position, most pronounced in working-side muscles. This pointed to shorter contractions with stable occlusion and is interpreted as the result of less need for stabilizing activity. It is concluded, that the correlations between occlusal stability and elevator muscle function are probably based on feedback mechanisms from periodontal pressoreceptors.

顎関節症における顎頭蓋筋の圧痛の発現様式

Palpation pains of head and neck muscles are important signs of craniomandibulardisorders (CMD). The purpose of this study was to clarify prevalences of palpation pains (PPs) of the muscles in 391 CMD patients. Relationship among PPs examined in different muscles were analyzed with the chi-square test and o-coefficient. The results obtained were as follows.1. Frequencies of PPs ranged from 8.2% for occipital muscle (OC) to 54.7% for medial pterygoid (MP). PPs of the other muscles in this study -superficial masseter (SM), lateral pterygoid (LP), deep masseter (DM), posterior digastric (PD), sternocleidmastoideus (SC), anterior temporalis (AT), posterior temporalis (PT), and trapezius (TR)- were ranked in decreasing order of prevalence.2. Mean rates accompanying the other muscle PPs of the individual muscles were ranged from 43.2% for MP to 81.1% for TR. The other muscles -OC, PT, AT, SC, DM, LP, and SM- were ranked in decreasing order of accompanying rate. That was almost in reverse order of prevalence. The prevalence and accompanying rate of PPs suggest that there was an order in onsets of the muscle disorders of CMD.3. There were strong relationship statistically between PPs of OC-TR, SM-DM, PD-SC, AT -PT, MP-LP, and PD-LP. Those would indicate each, pair of muscles had kinds of functional relations in mastication.These findings could contribute to understanding the muscle functions and the onset mechanisms of CMD.

上，下顎Ｓｉｎｇｌｅ Ｄｅｎｔｕｒｅ装着者のそしゃく運動の調節機序に関する筋電図学的研究

The wearers of either a maxillary or a mandibular single denture, which thereby opposes natural dentition, may have even greater problems clinically and neurophysiologically than do those who wear complete dentures or those with natural dentition. This study proposed to investigate how the complex interplay between exteroceptors and proprioceptors is affected by the control of feedback mechanism during mastication in the wearers of either a maxillary or a mandibular single denture. The subjects selected included six well-functioning wearers of a maxillary (G1) and a mandibular single denture (G2). Surface EMGs of bilateral masseter and posterior temporal muscles were recorded simultaneously with the use of the Sirognathograph (SGG) during the mastication of three different types of test foods, chewed on the habitual side. Data were statistically computed by means of analysis of variance.The results were as follows:1. The basal seat area in G1 was approximately 1.6 to 1.7 times as large as G2. However, there were no significant differences between G1 and G2 in muscle activity of maximal clench.2. In the SGG, significant differences between the chewing of hard and soft foods were shown in G2. The occluding phase time and the maximum lateral component of the chewing orbit decreased during the mastication of hard foods.3. Significant differences between G1 and G2 were seen in the EMG. GI showed a longer the burst duration outlasting tooth contact and greater values in the integrated EMG than G2, especially during the mastication of hard foods.4. All of the CV values in the EMG parameters were significantly greater in G2 than in Gl. The above results show that different types of feedback might influence the masticatory movement in the wearers of either a maxillary or mandibular single denture. It appears that thereis characteristic feedback behavior in the mandibular single denture, in that, the sensory input from both the denture supporting mucosa and the mechanoreceptors act to control the inhibition of muscle activities.