• Journal of Oral Medicine and Pain
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• v.12 no.1
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• pp.95-103
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• 1987

The purpose of this study was to evaluate the effect of occlusal splint on the electromyographic silent period duration of masseter muscle in patients with TM disorders. The author measured the Helkimo dysfunction index and masseteric silent period duration before and after 4 weeks splint therapy in 15 patients with TM disorders. The results were as follow: Before splint therapy, the mean durations of masseteric silent period in 15 patients with TM disorders were 50.7msec in left and 50.5msec in right. After 4 weeks splint therapy, the mean durations of masseteric silent period were 25.4msec in left and 26.5msec in right. In the correlation between Helkimo dysfunction index and masseteric silent period duration in before treatment, correlation coefficient is 0.675, p.<0.01. There is statistically significant correlation between Helkimo dysfunction index and masseteric silent period duration. Helkimo dysfunction index was significantly decreased after 4 weeks splint therapy (P<0.01) The masseteric silent period duration was significantly decreased after 4 weeks splint therapy (p<0.01).

• The Journal of the Korean dental association
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• v.55 no.5
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• pp.365-369
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• 2017

In clinical dentistry, botulinum toxin is generally used to treat the square jaw, bruxism, and temporomandibular joint diseases. Recently, this procedure has been expanded and applied for cosmetic purposes, and it is becoming a key task to be aware of the precise anatomical structure of the target muscles to be cautious during treatment and how to prevent side effects. Therefore, the purpose of this study is to observe the anatomical structure of the superficial layer of masseter muscle and to provide a most effective botulinum toxin injection method through clinical anatomical consideration. It was observed that the muscle belly of superficial part of the superficial layer was originated from the deep to the aponeurosis of masseter muscle and descend, then changed gradually into the tendon structure attaching to the inferior border of the mandible. In this study, we named this structure deep inferior tendon. This structure was observed in all specimens. We conclude that the use of superficial layer and deep layer injection should be considered to prevent paradoxical masseteric bulging in consideration of the deep inferior tendon of superficial part of superficial layer of masseter muscle.

• The Journal of Korean Academy of Prosthodontics
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• v.25 no.1
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• pp.195-204
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• 1987

The purpose of this study was to investigate the effect of occlusal splints on the masseteric silent period and the changes of the masseteric silent period after experimental bruxism with occlusal splints. In nine subjects, anterior occlusal splints were fabricated. The jaw-jerk reflex was induced by tapping over mandibular symphysis area with solenoid driven hammer and electromyogram of left masseter muscle was recorded. In the recorded electromyogram of left masseter muscle the silent period duration was measured. This procedure was done before insertion of anterior occlusal splints, after insertion of anterior occlusal splints, after 30 min experimental bruxism with anterior occlusal splints, and 3hr after removal of anterior occlusal splints. The result were as follows; 1. The mean silent period duration was increased after insertion of occlusal splints compared with the mean silent period duration before insertion of occlusal splints. 2. There was no change of the mean silent period duration after 30 min experimental bruxism with occlusal splints compared with the mean silent period duration after insertion of occlusal splints. 3. 3hr after the removal of occlusal splints, the mean silent period duration showed no difference from the mean silent period duration before insertion of occlusal splints.

• The Journal of Korean Academy of Prosthodontics
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• v.25 no.1
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• pp.205-212
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• 1987

The purpose of this study was to investigate the duration of the silent period of the masseter muscle in normal subjects after experimental bruxism. The material for this study consisted of 9 male subjects with an age range of 22-24 years who showed normal occlusion clinically and were free from any history or symptoms of temporomandibular joint dysfunction. A jaw-jerk was stimulated by tapping the mandibular symphysis during maximal voluntary clenching with a solenoid-driven hammer. And three separate silent period records were made from the left masseter muscle at the following times: at normal state, after experimental bruxism, 1 week after bruxism. The following conclusions were obtained: 1. The average value of the duration of masseteric silent period during maximal voluntary clenching was $33.62{\pm}1.86msec$ when tap force of approximate 650g was applied at normal state. 2. After experimental tooth grinding for 30 minutes, the duration of masseteric silent period increased to $46.29{\pm}4.40msec$. 3. Comparing the duration of silent period measured at normal state with that measured after 1 week, the duration of silent period showed reproducibility.

• Archives of Plastic Surgery
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• v.38 no.2
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• pp.173-181
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• 2011

Purpose: Masseter muscle is an important muscle of mastication. Because it has a great influence on the shape of low facial contour, patients who have masseteric hypertrophy show square-shaped jaw appearance. As aesthetic procedures for the reduction of the masseter muscle volume, radiofrequency ablation or botulinum toxin injection is at the center of attention. Authors studied the anatomical measurement of the thickness and width of masseter muscle and the surface mapping of the maximal thickness point using computed tomography (CT) scan to identify the useful guide for the injection of botulinum toxin in masseteric hypertrophy patients. Methods: We analyzed 2 mm-thickness OMU (ostiomeatal unit) CT of 112 normal people (224 masseter muscles) taken from June 2009 to May 2010. First, we measured the thickness, width and depth of the masseter muscle from the skin surface and analysed each by side, sex and age, respectively. The distribution of the thickness of the muscle and the correlation of thickness and width of the muscle were studied also. Second, we underwent surface mapping of the maximal thickness point using CT analysis by means of checking the vertical and horizontal distance from the angle of the mandible. Results: The average thickness and width of the masseter muscle was 17.73 mm and 40.78 mm in the male patients and were 14.33 mm and 37.42 mm in the female patients. Statistically, both figures of the male patients were larger than those of the female patients. However, the depth of the muscle from the skin surface in female patients (7.37 mm) was larger than that of the male patients (6.15 mm). There were no statistical difference in side or age. The width and thickness of the masseter muscle were in the positive correlation. The location of maximal thickness point of the masseter muscle was 27.77 mm vertically and 27.68 mm horizontally in the male patients, and 25.19 mm vertically and 25.42 mm horizontally in the female patients from the angle of mandible. Conclusion: We were able to present statistical evidence of the diagnosis and treatment of the masseteric hypertrophy regarding the anatomical measurements such as the thickness and width. And the maximal thickness point of the masseter muscle may be a useful guide for the clinical procedures of botulinum toxin injection.

• Journal of Oral Medicine and Pain
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• v.39 no.2
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• pp.55-62
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• 2014

Purpose: This study aims to evaluate the changes in soft tissue thickness of the masseteric region after injection of botulinum toxin type A (BTX-A). Methods: Twenty-four data acquired from medical records were classified into 4 groups: bruxer group that received masseter muscle injection only (M-B), bruxer group that received both masseter and temporalis muscle injections (MT-B), non-bruxer group that received masseter muscle injection only (M-NB) and non-bruxer group that received both masseter and temporalis muscle injections (MT-NB). Injection dose of BTX-A was 30 units for each masseter muscle and 20 units for each temporalis muscle. We measured the reduced thickness of the masseteric region before and after 12 weeks after injection using cone-beam computed tomography. Results: Among the patients that received both masseter and temporalis muscle injections, bruxer group showed a tendency to have more reduction in masseter muscle thickness than non-bruxer group. The difference in reduced thickness between M-B and MT-B tended to show greater than the difference between M-NB and MT-NB. Conclusions: In case of masseter hypertrothy patients with bruxism there was a tendency to show a difference in reduced thickness of soft tissue between the group that received both masseter and temporalis muscles injection and the group that received masseter muscle injection only hence a thorough inspection before the injection of BTX-A is condisered to be needed.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.50 no.11
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• pp.541-549
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• 2001

The term 'silent period(SP)' refers to a transitory, relative or absolute decrease electromyography(EMG) activity, evoked in the midst of an otherwise sustained contraction. Masseteric SP is elicited by a tap on the chin during isometric contraction of masseter muscle. In this paper, a new EMG signal generation model including SP in masseter muscle is proposed. This work is based on the anatomical structure of trigeminal nerve system that related on temporomandibular joint(TMJ) dysfunction. And it was verified by comparing the real EMG signals including SP in masseter muscle to the simulated signals by the proposed model. Through this studies, it was shown that SP has relation to variable neurophysiological phenomena. A proposed model is based on the control system theory and DSP(Digital Signal Processing) theory, and was simulated using MATLAB simulink. As a result, the proposed SP model generated EMG signals which are similar to real EMG signal including normal SP and an abnormal extended SP. This model can be applied to the diagnosis of TMJ dysfunction and can effectively explain the origin of extended SP.

• The korean journal of orthodontics
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• v.22 no.3 s.38
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• pp.617-626
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• 1992

This study was conducted for the assessment of the usefulness of masseteric silent period on electromyogram as a diagnostic method for temporomandibular disorder. Of students and dentists in Dental College of Yonsei University and patients, 36 experimental subjects with symptoms such as clicking bound, pain in the temporomandibular joint area and limitation of jaw movement, and 33 control subjects without such symptoms were selected for this study. On each subject electromyographic masseter muscle silent period followed by mention tap was recorded with surface electrodes and analysed with computerized system. The following results were obtained: 1. The mean silent period was $36.97{\pm}9.23$ msec in experimental group, and $25.62{\pm}5.24$ msec in control group respectively. 2. There were no statistically significant differences in silent period between male and female in either experimental and control group. 3. Silent periods in experimental group were more prolonged than those of control group. (P < 0.01) Taken all together, electromyographic masseter muscle silent period may be useful for diagnosis and evaluation of temporomandibular disorder.

• The Journal of the Korean dental association
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• v.15 no.3
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• pp.205-208
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• 1977

The etiology of masseteric hypertrophy is obscure. When the hypertrophy occurs unilaterally it's appearance is more striking because of the resultant facial asymmetry. Two soldiers were admitted with the complaint of a lump on their jaws. The authors obtained good results on the esthetic & functional aspect in two cases of unilateral masseteric hypertrophy with the Adam's method. The etiology was thought to be the combination of unilateral masticatory and jaw clenching habits when emotionally disturbed or under nervous tension in army services.

• Journal of Oral Medicine and Pain
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• v.45 no.4
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• pp.110-114
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• 2020

Myofascial pain (MFP) is one of the most common causes of persistent orofacial pain. Patients with chronic myofascial orofacial pain may present with diffuse heterotopic pain, complicating the correct diagnosis. Treatment of chronic MFP should focus on the elimination of aetiologic factors. This article describes two cases of chronic MFP of the masticatory muscles, whose symptoms were exacerbated after masseteric nerve neurectomy. The patients had suffered from irrelevant treatment which did not resolve the symptom. Their symptom was managed by conventional treatment protocol. These cases emphasize the importance of correct diagnosis and evidence-based approach.