• The korean journal of orthodontics
• /
• v.11 no.1
• /
• pp.25-30
• /
• 1981

Fifteen young pigs were used in this study. The animals were divided into three groups 1. Group for removal of the temporal muscle, 2. Group for removal of the masseter muscle, 3, Group for removal of masseter and internal pterygoid muscles. The animals were anesthetized with $3.5\%$ chloral hydrate intraperitoneally. In the right side the head was shaved. The masticatory muscle was removed. The animals were sacrificed four months later. The head was separated from trunk and cleaned by boiling in a solution of potassium hydroxide. The results were as follows; 1. In the group for removal of the temporal muscle, the Coronoid process of the mandible was resorbed. 2. In the group for removal of the masseter muscle, there was produced asymmetrical growth of the mandible, attrition of the molar teeth in the control side, and resorption of the mandibular angle. 3. In the group for removal of the Masseter and Internal muscles, the changes were more severe than that of the group for removal of the masseter muscle. The mandibular angle was completely absent. 4. The growth of the bone seems definitely related to the presence of the muscular tissue actively pulling upon it.

• Journal of Oral Medicine and Pain
• /
• v.22 no.2
• /
• pp.327-339
• /
• 1997

This study aimed at evaluating tile relationship between pressure pain threshold(PPT) and electromyographic(EMG) activity in 30 healthy volunteers and 30 patients with temporomandibular disorders. PPTs were determined with electric pressure algometry over masseter, temporalis anterior, sternocleidomastoid, and trapezius muscle during resting and clenching. To obtain more reliable result, two examiners measured PPTs two times on each muscles, randomly. Resting and clenching EMG activity and tenderness of all muscles were measured to evaluate the relationship with PPTs. The collected data were processed by SAS/STAT program. The obtained results were as follows : 1. Pressure pain thresholds in tendered muscles were lower than those in non-tendered muscles. This tendency was more prominant in masticatory muscles than in cervical muscles and in clenching than in resting. 2. There ware a tendency of higher PPTs in unaffected side than in affected side, but there were no significant difference statistically. 3. There wert no difference of PPTs between in preferred side and in ipsilateral side, significantly. 4. There was a significantly positive correlation between resting and clenching PPTs, but there were no correlation between PPTs and EMG activities. 5. Comparison of EMG activity between in higher group and in lower group by resting PPTs didn't show any significant difference. But resting EMG activity in the higher group of clenching PPTs were lower, on the contrary, clenching activity were higher than those in lower groups of clenching PPTs. From this results, the author concluded that the clenching PPTs was more important than resting PPTs in diagnosis of muscle dysfunction. And the author recommanded that all of three following test were performed for the proper diagnosis and treatment of orofacial Pain : muscle tenderness, EMG activity, and PPT.

• Journal of Oral Medicine and Pain
• /
• v.15 no.1
• /
• pp.117-124
• /
• 1991

The purpose of his study was to investigate the variations of occlusal contact pattern according to chewing side preference. The author selected 59 dental students (mean age 23.6 years) who had no signs and symptoms of masticatory disorders and divided into two groups, that is, bilateral chewing side group and unilateral chewing side group, respectively. For recording, T-Scan System(Teksan Inc., USA) was used and the recorded occlusal contacts were examined as to the number of occlusal contacts, points distribution in dental arch, time sequence and force snapshot. The obtained results were as follow s: 1. Total number of occlusal contacts were more in unilateral chewing side group and there were significant difference in number between right and left side or between chewing and less-chewing side in all two groups. 2. All items related to time sequence showed no statistical significant difference between two groups in any case. 3. Unilateral chewing side group had more occlusal contact force than bilateral group, especially in chewing side. From the above finding, the author considered that there was occlusal unbalance in unilateral chewing side group. 4. Chewing side preference would possibly have more effects on the occurrence rate of anterior tooth contact that the rate of prolonged their contact but proved.

• The Journal of Korean Academy of Prosthodontics
• /
• v.33 no.4
• /
• pp.718-730
• /
• 1995

This study was performed to measure the mandibular movement and the changes of masicatory and sternocleidomastoid muscle activity reflected by occlusal disturbance during habitual chewing. For this study, 18 subjects(14 males and 4 females with an average age of 24.0) were selected. The impression of each subject were taken for measuring intermolar distance on lower dentition. The activities of masticatory and sternocleidomastoid muscle and the mandibular movement were recorded and analyzed during habitual chewing by means of E.M.G.(electromyograph), E.G.N.(electrognathograph), rotate program in BioPak analyzing system(BioResearch Inc.). The results were as follows : 1. In EMG of the mandibular rest position, the mean value of muscle activites were increased by nocleidomastoid muscle and anterior belly of digastric muscle(0.05

• The korean journal of orthodontics
• /
• v.49 no.4
• /
• pp.254-264
• /
• 2019

Objective: To evaluate the short-term changes in masticatory muscle activity and mandibular movement patterns after orthognathic surgery in skeletal Class III patients with facial asymmetry. Methods: Twenty-seven skeletal Class III adult patients were divided into two groups based on the degree of facial asymmetry: the experimental group (n = 17 [11 male and 6 female]; menton deviation ${\geq}4mm$) and control group (n = 10 [4 male and 6 female]; menton deviation < 1.6 mm). Cephalography, electromyography (EMG) for the anterior temporalis (TA) and masseter muscles (MM), and mandibular movement (range of motion [ROM] and average chewing pattern [ACP]) were evaluated before (T0) and 7 to 8 months (T1) after the surgery. Results: There were no significant postoperative changes in the EMG potentials of the TA and MM in both groups, except in the anterior cotton roll biting test, in which the masticatory muscle activity had changed into an MM-dominant pattern postoperatively in both groups. In the experimental group, the amount of maximum opening, protrusion, and lateral excursion to the non-deviated side were significantly decreased. The turning point tended to be shorter and significantly moved medially during chewing in the non-deviated side in the experimental group. Conclusions: In skeletal Class III patients with facial asymmetry, the EMG activity characteristics recovered to presurgical levels within 7 to 8 months after the surgery. Correction of the asymmetry caused limitation in jaw movement in terms of both ROM and ACP on the non-deviated side.

• Journal of Oral Medicine and Pain
• /
• v.18 no.1
• /
• pp.21-29
• /
• 1993

The purpose of this study was to evaluation of temporomandibulr joint space according to increasing the occlusal force on working and non-working side during unilateral bite. For the study, 22 normal adults, age ranged from 23 to 25, who had no symptoms on TMJ area and masticatory muscles and had normal or class I molar relationship were selected. Transcranial TMJ radiograph was taken during unilateral biting with sensor of Bite force checker (Nihon Kohden Kygyo Co.Ltd., Japan) on each 1st molar teeth of right and left side which were forced each 0Kg, 10Kg, 20Kg and 30Kg by use of Accurad-200 (Denar Corperation's product). The radiographs were traced on the screen, which was magnified by 5. The size of temporomandibular joint space at anterior, superior and posterior compartment were measured with Dumas's method (reference line of between squamotympanic fissure and the most inferior point of articular eminence). On the basis of this study, the following results were obtained. 1. Size of anterior TMJ space was tend to decrease on the working side and increase on the non-working side according to increasing the occlusal force, but not significant statistically (p>0.05). 2. Size of superior TMJ space was tend to increase on the working side and decrease on the non-working side according to increasing the occlusal force (p<0.05). 3. Size of posterior TMJ space was tend to decrease on both working ad nonworking side, but non significant statistically.

• The Journal of Korean Academy of Prosthodontics
• /
• v.36 no.2
• /
• pp.245-257
• /
• 1998

This study was performed to measure the changes of the mandibular movement and the masticatory muscular activities - anterior temporal and masseter muscle of both side - reflected by intentional increase of anterior guidance angie. For this study, 5 volunteers (3 males and 2 females with average age of 24.0) were selected. Each volunteer had Angle's classification I and did not have any missing tooth except third molar and any extensive restorations. Metallic guide plate was made at volunteer's working model fabricated by improved dental stone and cemented to the palatal surface of maxillary central incisor using resin cement(Panavia $21^{(R)}$) and then adjusted not to give any occlusal interferences at intercuspal position. The activity of masticatory muscles and the changes of mandibular movement were recorded by EMG and Sirognathograph in Biopak analysing system(Bioresearch Inc., Milwaukee, Wisconsin, USA). Measurement was done at before experiment, immediatley after placement, 1 week after placement, immediately after removal, and 1 week after removal. The results were as follows: 1. Moderate phonetic disturbance and mild headache were occured to 3 volunteers for 2 days after setting and 1 volunteer had positive reaction to percussion and slight midline diastema. But all of these clinical signs were diappeared 1 week after removal and the other volunteer did not have any special clinical sign. 2. In the EMG of the mandibular rest position, the mean value of anterior tempotal muscle was increased immediately after placement(p<0.01) and then decreased 1 week after placement(p<0.05) and increased 1 week after removal(p<0.05) but not recovered as before experiment. The mean value of masseter muscle was decreased during the experiment period. 3. In the EMG during mandibular protrusive movement, all muscular activity was decreased during the experiment period. Reduced activity was not recovered 1 week after removal(p<0.03). 4. During the habitual opening, anteroposterior movement of mandible was decreased immediately after placement(p<0.05) and then increased 1 week after placement but not statistically significant(p>0.1). Vertical movement was not shown significant difference during the experiment period(p>0.1). Lateral movement was decreased immediately after placement(p<0.05) and then increased 1 week after placement but not recovered as before experiment. The opening and closing velocity of mandible was shown minor changes but not statistically significant. 5. During the habitual opening, anteroposterior movement of mandible was decreased 1 week after placement(p<0.05) and then increased immediately after removal and recovered 1 week after removal as before experiment. Vertical movement was not shown significant changes. Lateral displacement of mandible was increased continuously and recovered 1 week after removal. Opening velocity was temporarily increased immediately after removal but recovered and closing velocity was not shown significant changes. 6. During the right side chewing, anteroposterior movement of mandible was increased immediately after removal but recovered and vertical movement was not shown statistically significant results. Lateral displacement and velocity of mandible were not shown significant results. 7. During the left side chewing, the changes of mandibular movement pattern were not shown statistically significant results.

• Journal of Oral Medicine and Pain
• /
• v.13 no.1
• /
• pp.23-33
• /
• 1988

The purpose of this study was to standardized and classify the coordination pattern among the chewing side and non-chewing side masseter and anterior muscles, in terms of EMG values on lateral excursion, clenching, and mastication in presence of the non-chewing side. In this study, 25 subjects were selected for experiment of lateral excursion, clenching and mastication and EMG value of the masseter and anterior temporal muscle on both sides were recored 2 times respectively. The bioelectric processor model EM2(Myo-tonic research, INC. U.S.A.) with the surface electrodes were used to record the EMG activity during all experimental procedures. The results were as follows : 1. During lateral excursion on intereference of non-chewing side, the EMG values of the temporal muscle were significantly more prominent than those of the temporal muscle on the non-chewing side. The EMG values of non-chewing side were significantly more prominent than those of chewing side on the both side masseter muscle and those of chewing side were significantly more prominent than those of non-chewing side on the both side temporal muscle. 2. During clenching on the occlusal interferance, the EMG values of non-chewing side masseter muscle were most prominent. 3. During mastication on the occlusal interferance, the EMG values of the chewing side temporal muscle were most prominent and those of non-chewing side temporal muscle were the lowest. 4. The EMG values of temporal muscle of non-chewing side on interferance were significantly more prominent than those of canine guidance during lateral excursion. 5. During clenching on the occlusal interferance, the EMG values of the masseter and the temporal muscles of the non-chewing side were significantly more prominent than canine guidance, but those of chewing side temporal muscle on canine guidance were significantly more prominent than those of interferance. 6. During mastication on canine guidance, the EMG Values of the temporal muscle on the chewing side, the masseter muscle on the chewing side and the temporal muscle on the non-chewing side were more prominent than those of interferance, but temporal muscle of non-chewing side was not different between canine guidance and occlusal interferance on non-chewing side.

• Journal of Oral Medicine and Pain
• /
• v.30 no.1
• /
• pp.45-55
• /
• 2005

As people prefer to use right or left hand, some have preferred chewing side while others do not. Totally, 82 volunteers composed of students and staffs from Dental Hospital College of Dentistry Yonsei University participated in this study for the investigation of influence of preferred chewing habit, that has lasted for more than a year, on electromyographic(EMG) activity of masticatory muscles and bite force. Among the 82 volunteers, 46 had preferred chewing habit while the other 36 did not. Prior to the investigation, those with factors that could affect the study, such as, general disease, irregular dentition and malocclusion, were screened and excluded by questionnaire and clinical examination. The results were as follows: 1. There was no significant difference in EMG activities between chewing side and non-chewing side of preferred chewing subjects at rest as well as maximal voluntary contraction(MCV)(p>0.05). 2. Asymmetrical coefficient of temporal and masseter muscle EMG activities between preferred chewing subjects and non-preferred chewing subjects at rest was not significantly different(p>0.05). 3. Asymmetrical coefficient of masseter EMG activity was significantly higher(p<0.05) than that of non-preferred chewing subjects at MCV, whereas that of anterior temporal muscle showed no difference(p<0.05). 4. In preferred chewing subjects, there was no significant difference in average bite force and occlusal contact area between chewing side and non-chewing side(p>0.05). 5. There was no significant difference in Asymmetrical coefficients of average bite force and occlusal contact area between preferred chewing subjects and non-preferred chewing subjects (p>0.05). Consequently, preferred chewing habit can be considered as physiological asymmetry with normal function rather than to have influence on EMG muscle activity of masticatory muscles, average bite force and occlusal contact area. Objective standardization to differentiate preferred chewing subjects and non-preferred chewing subjects should be established in the further study.

• The Journal of Korean Physical Therapy
• /
• v.35 no.6
• /
• pp.185-189
• /
• 2023

Purpose: This study investigated the immediate biomechanical effects of unilateral mastication for 10 minutes on the temporomandibular joint (TMJ) with 21 healthy adult participants. Methods: The gum group chewed gum on the right side for 10 minutes, and the control group rested for 10 minutes. Biomechanical data were obtained using a three-dimensional infrared camera before and after intervention. An independent t-test assessed the variation of kinematic data to identify differences between before and after intervention. Results: Among biomechanical variables, the gum group's length of the left forehead middle region and the temporomandibular joint angle decreased compared to the control group (p<0.05). Conclusion: Caution with unilateral masticatory activity is recommended, as unilateral mastication causes biomechanical changes due to excessive load on the soft tissues of the contralateral TMJ.