• The Journal of Korean Academy of Prosthodontics
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• v.40 no.6
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• pp.577-589
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• 2002

There are several variations in normal mastication. In them, unilateral mastication is chewing, predominantly on a preferred side of the dentition and hardly on e non-preferred side. Continual unilateral mastication may alter the coordination of masticatory muscles. Although they studied about these EMG of masticatory muscles, there were no information about characteristics of masticatory muscle activity in unilateral mastication. Therefore, In this study, we investigated the activity of the masseter and anterior temporal muscles during rest, clenching in maximum intercuspation and gum chewing in habitually unilateral mastication group compared with normal group and tried to know effects of continual unilateral mastication on activity of masticatory muscles. The results of this study were as follows 1. In electromyographic activity during rest, in bilateral mastication group pattern of muscle activity of right and left side was symmetrical. But, in unilateral mastication group, records of anterior part of temporal muscle was higher than that of bilateral mastication group (p<.01) and patterns of muscle activity of right and left side in both muscle were asymmetrical.(p<.05) 2. In electromyographic activity during clenching in maximum intercuspation, records of superficial part of masseter muscle were higher than anterior part of temporal muscle in both group. Muscle activity of temporal muscle in unilateral mastication group was a little higher han bilateral mastication group and asymmetry of activity pattern in temporal and masseter muscle was shown but these differences were not statistically significant. (p<.05) 3. In electromyographic activity during gum chewing, temporal muscle was activated earlier than masseter muscle and maximum bite force is derived from masseter muscle in both group. In unilateral mastication group, electromyographic activity of masseter and temporal muscle of preferred chewing side, regardless of right or left side chewing, was higher than that of bilateral mastication group and especially, difference in masseter muscle was statistically significant. (p<.01) Based on the above results, our study suggested that recording of masticatory muscle activity will be helpful in the effective diagnosis and treatment of some types of the parafunctional habits.

• The Journal of Korean Academy of Prosthodontics
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• v.25 no.1
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• pp.269-279
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• 1987

The purpose of this study was to obtain basic data needed to clinical diagnosis and treatment by investigating the occlusal wear facets and those related factors. Sixty-six subjects, ranging from 24 to 26 years of age without symptoms of stomatognatic system, were selected from dental students in Chosun University. The area of occlusal wear facets was measured and twenty subjects were selected, and divided into two groups (Group I and Group II). The Group I had small facet areas, and the Group II had large facet areas. These two groups were investigated into right and left side wear facet areas, vertical overlaps, occlusion types of working side, masticatory muscle activities, and asymmetry of right and left side masticatory muscle function. The results were as follows: 1. The average wear facet areas of all subjects was $22.84{\pm}88.95mm^2$, and Group I and Group II were $96.12{\pm}32.00mm^2$ and $372.94{\pm}65.63mm^2$ respectively. 2. The right and left wear facet areas of Group I were $46.72{\pm}14.36mm^2$ and $49.40{\pm}21.46mm^2$ respectively. The right and left wear facet areas of Group II were $175.27{\pm}45.75mm^2$ and $185.69{\pm}45.37mm^2$ repsectively. 3. The vertical overlap of Group I and Group II was $3.88{\pm}0.81mm$ and $2.88{\pm}1.14mm $ respectively. 4. Most of the Group I had Canine protection occlusion (80%), and most of the Group II had Group function occlusion (80%). 5. The masticatory muscle activities at rest position, maximum bite, habitual chewing, right and left unilateral chewing were greater in Group II than in Group I, especially in the masseter muscle of working side at right and left unilateral chewing. (P<0.01). 6. The asymmetry of right and left wear facets and masticatory muscle activities were greater in Group II than in Group I. (P<0.01).

• The Journal of Korean Academy of Prosthodontics
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• v.36 no.4
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• pp.533-548
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• 1998

The purpose of this study was to investigate the influence of balancing interference on the mandibular movement and masticatory muscle activity. 5 subjects(male. average age of 24.3) without dysfuction in masticatory system were selected. The balancing interference was provided by construction of cast metal crown and onlay on the upper and lower first molars. Clinical examination, changes displacement and velocity, and muscle activity were recorded and analyzed by means of BioPak system(Bioresearch Inc., Milwaukee Wisconsin. USA). The results were as follows ; 1. In clinical examination, various symptoms were reported by all subjects after application of interference. Almost symptoms were subsided after elimination of interference. 2. In the border movements in frontal plane, lateral border movement toward non-interference side was changed according to the interference after application of interference. Immediately after removal of interference, border movements' pattern was recovered as same as before experiment. 3. During gum chewing on the non-interference side, horizontal movement was decreased immediately after application of interference(p<0.05). 1 week after application of interference, horizontal movement was more decreased in 3 subjects and showed a chopping type masticatory stroke. But in 2subjects, horizontal movement was increased to avoid interference. 4. In EMG of the mandibular rest position, no significant changes were showed in the experiment period(p>0.05). 5. During gum chewing on the interference side, the activity of opposite temporal muscle was increased immediately after application of interference(p<0.05). 1 week after application of interference. The activity of ipsilateral temporal muscle and left and right masseter muscles was increased (p<0.05). 1 week after elimination of interference, increased muscle activity was recovered about the same level as before experiment. 6. During gum chewing on the non-interference side, 1 week after application of interference, the activity of ipsilateral temporal muscle was increased (p<0.05). 1 week after elimination of interference. increased muscle activity was returned about the same level as before experiment.

• Journal of Oral Medicine and Pain
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• v.34 no.3
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• pp.317-324
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• 2009

This study aimed to assess stiffness and elasticity of the masticatory muscle in the patients with the masticatory muscle pain using a tactile sensor and to investigate whether the masticatory muscle pain affects the facial expression muscles. From those who visited Department of Oral Medicine in Dankook University Dental Hospital, 27 patients presenting with unilateral muscle pain and tenderness in the masseter muscle (Ms) were selected (mean age: $36.4{\pm}13.8$ years). Exclusion criterion was those who also had temporomandibular joint (TMJ) disorders or any neurological pain. Muscle stiffness and elasticity for the muscles of mastication and facial expression was investigated with the tactile sensor (Venustron, Axiom Co., JAPAN) and the muscles measured were the Ms, anterior temporal muscle (Ta), frontalis (Fr), inferior orbicularis oculi (Ooci), zygomaticus major (Zm), superior and inferior orbicularis oris (Oors, Oori) and mentalis (Mn). t-tests was used to compare side difference in muscle stiffness and elasticity. Side differences were also compared between diagnostic groups (local muscle soreness (LMS) vs myofascial pain syndrome (MPS) and between acute (< 6M) and chronic ($\geq$ 6M) groups. This study showed that Ms and Zm at affected side exhibited significantly increased stiffness and decreased elasticity as compared to the unaffected side.(p<0.05) There was no significant difference between local muscle soreness and myofascial pain syndrome groups and between acute and chronic groups. The results of this study suggests that masticatory muscle pain in Ms can affect muscle stiffness and elasticity not only for Ms but also for Zm, the facial expression muscle.

• Journal of Oral Medicine and Pain
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• v.47 no.4
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• pp.217-221
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• 2022

Neurogenic muscular atrophy is muscle wasting and weakness caused by trauma or disease of the nerve that innervates the muscle. We describe a case of unilateral trigeminal neuropathy and neurogenic muscular atrophy of the masticatory muscle caused by a tumor in the foramen ovale. A 59-year-old man visited our clinic complaining of difficulty in right-sided mastication. There were no evident clinical signs and symptoms of temporomandibular disorder. However, severe atrophy of the right masseter and temporalis muscles and hypesthesia of the right side mandibular nerve area were confirmed. Through T1 and T2 signals on magnetic resonance imaging (MRI), a mass suspected of a neurogenic tumor was observed in the foramen ovale and cavernous sinus. Severe atrophy of all masticatory muscles on the right side was observed. This rare case shows trigeminal neuropathy caused by a tumor around the foramen ovale and atrophy of the ipsilateral masticatory muscles. For an accurate diagnosis, it is essential to identify the underlying cause of muscle atrophy with neurologic symptoms present. This can be done through a more detailed clinical examination, including sensory testing and brain MRI, and consider a referral to neurology or neurosurgery for the differential diagnosis of the intracranial disorder.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.46 no.5
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• pp.313-320
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• 2020

Objectives: The aim of this study was to evaluate the relationship between masticatory muscle thickness and mandibular morphology in young Korean adults with normal occlusion and mandibular prognathism. Patients and Methods: Multidetector computed tomography (MDCT) was used to measure the masticatory muscle thickness on the right side in 100 Korean young adults (50 normal occlusion group, 50 mandibular prognathism group). Cephalometric analysis was done to measure mandibular morphology. Pearson correlation analysis was done to investigate the relationship between the masticatory muscle thickness and mandibular morphometry. Results: The four masticatory muscles showed positive correlation with intergonial width in all subjects. All muscles, except temporalis, positively correlated with height of the ramus and mandibular length. Positive correlation was also observed in all muscles, except medial pterygoid, with thickness of the ramus. In the normal occlusion group, all four masticatory muscles showed positive correlation with intergonial width and ramus thickness. Positive correlation was also observed in all muscles (except lateral pterygoid) with mandibular length. Masseter and lateral pterygoid positively correlated with height of the ramus. In the mandibular prognathism group, all masticatory muscles, except lateral pterygoid, showed positive correlation with intergonial width. The masseter muscle showed negative correlation with ANB. Conclusion: The results suggest a positive correlation of the thickness of masticatory muscles with both horizontal and vertical dimensions of the mandible. However, thickness of the masseter was found to decrease in patients with increasing severity of mandibular prognathism.

• Journal of Oral Medicine and Pain
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• v.17 no.1
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• pp.41-50
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• 1992

The authors performed a experimental study to evaluate the effects of masticatory muscle fatigue on tooth contact and masticatory muscle activity in 26 normal healthy women. The experimental masticatory muscle fatigue was induced by unilateral biting of 5kg force on mandibular first molar. The results were as follows : 1. The initial symptom related to muscle fatigue pain appeared in 85.19 seconds of isometric contraction and the endurance time of isometric contraction was 203.15 seconds. 2. The pain occurred more frequently in masseter region than in temporal region. In masseter pain the incidence was almost equal between both sides, whereas the temporal pain was more in contralateral side. 3. The spontaneity and the symmetry of tooth contact during maximum clenching were reduced after isometric unilateral biting. 4. After induction of experimental muscle fatigue, the EMG activities of masseter muscles of both sides and ipsilateral temporal muscle showed the tendency of decreasing activities. 5. The asymmetry indicies of masseter and temporal muscles were reduced after isometric bilateral biting.

• Journal of Oral Medicine and Pain
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• v.26 no.1
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• pp.75-85
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• 2001

This study was performed to investigate the effect of mandibular midline shift and difference of mandibular height between both sides on the electromyo- graphic(EMG) activity of the masticatory muscles on clenching or gum chewing movement. For this study, 105 patients with temporomandibular disorders(TMD) were selected and panoramic radiograph were taken. Amount and side of the midline shift and height of the mandible from antegonial notch to the top of the condylar head were measured on panoramic view. $BioEMG^{(R)}$ (Bioresearch Inc., Milwaukee, USA) was used for recording of EMG activity(${\mu}V$) of the anterior temporalis and the superficial masseter on clenching or gum chewing movement. EMG activity on clenching during 533msec period were measured for activity of the starting point and the one second-after activity as the early EMG and the maximum EMG, respectively. EMG activity on gum chewing movement were measured for activity of the first and the second chewing stroke. The data collected were analysed by SPSS windows program, and the results of this study were as follows : 1. Height of the mandible was 8.06cm on right side and 8.03cm on left side, and showed no difference by age, but significantly differed by sex with higher in male subjects. 2. Mean value of the midline shift was 0.1mm with range of 0~5mm on both sides. The amount and side of the midline shift did not related with height difference of the mandible and/or the EMG activity of the masticatory muscles on clenching. 3. Prevalence of higher right side and higher left side of the mandible were almost same, and the EMG activity of higher side was not higher than that of the other side. 4. In the subjects with height difference of more than 5mm between both sides of the mandible, the early EMG activity on clenching were differed for the anterior temporalis, but the maximum activity were differed for the superficial masseter. 5. In the subjects with height difference of more than 5mm between both sides of the mandible, EMG activity of the anterior temporalis of the gum chewing side was not higher than that of the other side when chewing on the side of lower height, but in the subjects with height difference of less than 5mm, the EMG activity was higher than that of the other side.

• Journal of Oral Medicine and Pain
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• v.43 no.4
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• pp.147-151
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• 2018

Disuse atrophy involves gradual muscle weakening due to inadequate usage and can cause temporomandibular disorder (TMD). A 45-year old man with TMD symptoms on the left side, who had disuse atrophy of the masticatory muscles on the right side following surgical removal of a trigeminal schwannoma on the right side, first visited the Department of Orofacial Pain and Oral Medicine at Kyung Hee University Dental Hospital with left jaw pain and difficulty in opening mouth and chewing. He had been experiencing difficulties in cognitive function, decrease in visual acuity, impaired speech, and writing deficits after brain surgery. Furthermore, he complained of abnormal occlusion on the right side, which interfered with his ability to chew comfortably and open his mouth effectively. Herein, we describe a contralateral TMD case due to ipsilateral disuse atrophy after brain surgery for a trigeminal schwannoma and our successful treatment with medication, physical therapy, and stabilization splint.

• The Journal of Korean Academy of Prosthodontics
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• v.36 no.3
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• pp.427-452
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• 1998

To elucidate the effects of food texture such as hardness, cohesiveness, adhesiveness on mastication procedure, the electromyographic activity (EMG) of the masticatory muscles and the chewing movements were analyzed in eighteen young subjects during ordinary chewing. Seven different foods were selected by sensory texture profiling and mechanical test with texturometer; egg white, sausage, pizza cheese, yang-geng, biscuit, peanut and almond. The indexes of jaw movements used were the chewing number, chewing time, maximum opening, average opening, closing velocity and opening velocity. The EMG indexes analyzed were maximum and average integrated amplitude of the anterior temporal and masseter muscles. The results obtained were as follows. 1. The chewing time and chewing number, mandibular displacement and mandibular movement velocity were not changed by the hardness, cohesiveness and adhesiveness of the food (p>0.05). 2. The harder food materials showed a higher amplitude of the anterior temporal muscle integrated EMGs than the softer ones (p<0.05). 3. The maximum and average integrated EMGs of the masseter muscle increased with the increase of hardness of the food (p<0.05). 4. The integrated EMGs of preferred side and non-preferred side masticatory muscles increased with the increase of hardness of the food (p<0.05). 5. The adhesiveness and cohesiveness of the food were not the determining factor to the integrated EMGs of masticatory muscles (p<0.05).