• Journal of Periodontal and Implant Science
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• v.46 no.2
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• pp.96-106
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• 2016

Purpose: Stress distribution and mandible distortion during lateral movements are known to be closely linked to bruxism, dental implant placement, and temporomandibular joint disorder. The present study was performed to determine stress distribution and distortion patterns of the mandible during lateral movements in Class I, II, and III relationships. Methods: Five Korean volunteers (one normal, two Class II, and two Class III occlusion cases) were selected. Finite element (FE) modeling was performed using information from cone-beam computed tomographic (CBCT) scans of the subjects' skulls, scanned images of dental casts, and incisor movement captured by an optical motion-capture system. Results: In the Class I and II cases, maximum stress load occurred at the condyle of the balancing side, but, in the Class III cases, the maximum stress was loaded on the condyle of the working side. Maximum distortion was observed on the menton at the midline in every case, regardless of loading force. The distortion was greatest in Class III cases and smallest in Class II cases. Conclusions: The stress distribution along and accompanying distortion of a mandible seems to be affected by the anteroposterior position of the mandible. Additionally, 3-D modeling of the craniofacial skeleton using CBCT and an optical laser scanner and reproduction of mandibular movement by way of the optical motion-capture technique used in this study are reliable techniques for investigating the masticatory system.

• Journal of Oral Medicine and Pain
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• v.38 no.4
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• pp.325-331
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• 2013

Botulinum neurotoxin(BoNT) is a protease exotoxin produced from Clostridium botulinum. It works by blocking the release of acetylcholine from cholinergic nerve endings causing inactivity of muscles or glands. Recently, the therapeutic use of BoNT have expanded to include a wide range of medical and dental conditions. Botulinum neurotoxin type A(BoNT/A) is used off-label in the orofacial region to treat primary and secondary masticatory and facial muscle spasm, severe bruxism, facial tics, orofacial dyskinesias, dystonias, and hypertrophy of the masticatory muscles. Local hematoma, infection, and persistent pain in the injection site are the site-of-injection side effects. Medication-related side effects are adjacent muscle weakness, slurred speech, an alteration in the character of the saliva, and severe headaches. In most cases, these complications are not persistent and bothersome. We reported a case report of a patient who had transient anterior open bite after BoNT/A injection on masseter muscles to treat the refractory myofascial pain.

• Journal of Korean Dental Science
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• v.7 no.1
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• pp.16-24
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• 2014

Purpose: This study was planned to clarify a negative view of chewing gum due to the concern that continuous gum chewing might cause a change in the gonial angle and make the lower facial appearance look square. Materials and Methods: We had 25 adults (13 males and 12 females, with an average of 27.3 years) chew 6 g of gum (spearmint) evenly with both right and left posterior teeth for one hour per day for three months. We then measured their gonial angle, the inclination of occlusal plane, facial height, bone marrow density, and masticatory force before chewing, 1, 2, and 3 month after chewing to verify its significance statistically. Result: The results showed that the gonial angle increased from $122.7^{\circ}$ to $123.3^{\circ}$ (P>0.05), and thus the jaws became slightly slimmer. There was no change in the occlusal plane inclination and facial height. Meanwhile bone marrow density in the mandibular angle and ascending ramus increased from $0.285g/cm^2$ to $0.290g/cm^2$ (P<0.05), and masticatory force also increased by 0.5 kg on the right side and 0.8 kg on the left side (P<0.05). Conclusion: Continuous chewing of gum gives an appropriate exercise effect to the stomatognathic system. As chewing gum has effect on increase bone marrow density without changing the mandibular angle and facial appearance the claim that jaw bone changes to a square jaw through chewing gum is regarded to be groundless.

• Journal of Oral Medicine and Pain
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• v.18 no.1
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• pp.55-62
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• 1993

The author has synchronously recorded the average electromyographic activities of the sternocleidomastoid muscles, the anterior temporal muacles and the masseter muscles. The marious levels of occlusal force were checked during clenching the resin plates which are made to fit each of the maxillary and the mandibular teeth. These activities were recorded in order to study the EMG activity pattern of the sternocleidomastoid muscle during the masticatory function of the jaw in 11 healthy subjects. The obtined results were as follows : 1. The electromyographic activities of the sternocleidomastoid muscles, the anterior temporal muscles and the masseter muscles were increased as the occlusal force increased, and the sternocleidomastoid muscles have a lineal correlationship with the occlusal force. 2. The sternocleidomastoid muscles and the masseter muscles showed higher EMG activity during clenching at the ventroflexed head position rather than at the extended head position. (p<0.05) However the EMG activities of the anterior temporal muscles showed no difference between the ventroflexed position and the extended position of the head. 3. The electromyographic activities of the sternocleidomastoid muscles, the anterior temporal muscles and the masseter muscles during clenching are similar at the habitual position and at the retruded condylar position. 4. The electromyographic activities of the sternocleidomastoid muscles, the anterior temporal muscles and the masseter muscles on the working side during mastication of gum and almonds are significantly higher than on the balancing side except the masseter muscles during mastication of almonds. (p<0.05, P<0.01) 5. The asymmetry of gum are lower than that during mastication of almonds. (p<0.05) The asymmetry indices of the sternocleidomastoid muscles are higher than those of the anterior temporal muscles and masseter muscles.

• Journal of Oral Medicine and Pain
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• v.23 no.2
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• pp.143-155
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• 1998

This study was performed to investigate the factor that might affect mandibualr body rotation. For the study, 115 patients with temporomandibular disorders and 35 dental students without angy signs and symptoms of temporomandibular disorders were randomly selected as the patient group and the contreol group, respectively. Preferred chewing side, Angle' classification, lateral guidance pattern, and affected side were clinically recorded, and the amount of Mandibular body rotational torque movement was measured in wide opening and closure, in right and left excursion with vertical and lateral distance in frontal plane, right and left rotational angel in horizontal and in frontal plane. Masticatory muscle activity of anteriorocclusal contact pattern on maximal hard biting were also observed synchronously with BioEMG and T-Scan , respectively. The observed items were muscle activity of anterior temporalis and superficial masseter, and tooth contact status related to contact number, force, duration, and occlusal unbalance between right and left arch. The data collected were analyzed by SAS statistical program. The results of this study were as follows : 1. Mean value of vertical distance in frontal plane in wide opening and closure was more in control subjects than in patients, but there was no difference for rotational angle. In right excursion, rotational angles were greater in patient group than in control group. 2. Comparison among the subjects by preferred chewing side did not reveal any significant difference, but comparison among patients by affected side showed more rotational amount in bilaterally affected patients than in unilaterally affected patients. 3. Comparison among the subjects by Angle's classification or lateral guidance pattern revealed no difference. There was also no difference between preferred chewing side and contralateral side, and between affected side and contralateral side. 4. Positive correlation in madibular rotational torque movements were observed among vertical distance, total horizontal rotation angle, electromyographic activity of anterior temporalis, tooth contact number, and tooth contact force but total frontal rotation angle almost did not show any correlation with other variables except vertical distance.

• Journal of Oral Medicine and Pain
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• v.17 no.2
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• pp.27-35
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• 1992

The purpose of this study was to evaluate the size of the temporomandibular joint space by the increase of the occlusal force on the working side and the non-working side during unilateral biting. For the study, 22 normal adults, age from 23 to 25, who had normal or class I molar relationship and had no symptoms on TMJ area and masticatory muscles were selected. Transcranial TMJ radiograph was taken during unilateral biting with the sensor of occlusal load measuring device (MPM-3000 ; Nihon Kohden Kogyo Co. Ltd., Japan) on 1st molar teeth of right and left side given to force of 0kg, 10kg, 20kg and 30kg respectively with Accurad-200(Denar Corperation's product). The radiographs were traced on the screen, with enlaged as 5 times. The size of temporomandibular joint space at anterior, superior and posterior compartment were measured with Dumas's method (reference line between squamotympanic fissure and the lowest point of articular eminence). The following results were obtained by this study. 1. The size of anterior TMJ space showed a tendency to decrease on the working side and increase on the non-working side by the increase of the occlusal force, but had no statistical significancy (P>0.05). 2. The size of superior TMJ space showed a tendency to increase on the working side and decrease on the non-working side by the increase of the occlusal force (P<0.05). 3. The size of posterior TMJ space showed a tendency to decrease on both working and nonworking side, but had no statistical significancy (P>0.05)

• Journal of Oral Medicine and Pain
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• v.35 no.1
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• pp.83-91
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• 2010

Objectives: This study aimed to assess the characteristics of temporomandibular disorder (TMD) symptoms and to determine the correspondence between TMD symptoms and clinical examination findings. Material and methods: A total of 218 patients (143 females and 75 males; age=$31.3{\pm}14.0$) were enrolled in this study who completed a questionnaire and underwent a clinical examination and radiographic assessment. Patients were asked about all the symptoms and complaints, including onset or duration, and locations of the symptoms. Clinical examination included amounts of mouth opening, palpable temporomandibular joint (TMJ) sounds, and tenderness to palpation of the TMJ and all masticatory muscles. Tenderness scores obtained from palpation of the masticatory system were summated to define the variables for further analysis. Results: Pain was the most frequently reported symptom (78.9%), followed by joint sounds (45.4%), and limitation in mouth opening (17.0%). Jaw pain comprised 91.9% of pain complaints. The subjective intensity of jaw pain was low to medium in most patients (93.7%), but it was poorly correlated with the sum of tenderness scores of the TMJ and masticatory muscles (Kendall tau = 0.084). In contrast, the side in which pain was reported by patients was well associated with the clinical examination results (pain of the right side, p < 0.001, and left side, p < 0.001). There was moderate agreement in TMJ sounds between the side identified by patients as symptomatic and clinical examination findings (kappa = 0.482). Finally, patients who complained of restricted mouth opening showed about a 10 mm less opening in all three measurements, compared to other patients (p < 0.001). Conclusion: The most frequent symptoms reported by TMD patients were jaw pain, TMJ sounds, and mouth opening limitation. The side of jaw pain, the side of TMJ sounds, and the presence of opening limitation were highly concordant between symptom reports and examination findings.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.34 no.3
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• pp.293-299
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• 2008

Bite force is created by the force of adjacent teeth accompanied with tension of masticatory muscle. The bite force value is greater in male than in female and ha maximum value at first molar. Masseter muscle is associated with bite force and during muscle contraction the electric signal is expressed in EMG form. The aim of the study is to assess recovery time for masseter muscle activity and according to each part of bite force after open reduction with internal fixation when mandibular angle fracture and subcondyle fracture occurred. And to determine the appropriate period for mandibular fracture patients to have normal masticatory activity. 30 patients with normal bite condition was selected for control group and from April, 2007 to September, 2007, 20 patients who visited our department of oral and maxillofacial surgery of Dankook University, were selected for the study and were diagnosed as mandibular angle fracture and subcondyle fracture. For control group, the bite force for incisors, canine, premolars and molars and activity of the masseter muscle was measured and compared for 1, 2, 3, 4, 6 and 8 weeks. That was divided as fracture side and normal side. Mann-Whitney U test was performed for significant difference and the following result was obtained. 1. The maximum voluntary bite force for incisors, canine, premolars and molars portion were 0.113 kN, 0.182kN, 0.295kN and 0.486kN and the masseter muscle activity was 0.192 volts in the control group. 2. The maximum bite force at fracture side was recovered by 4th weeks for incisors, 6th weeks for canine and premolars and 8th weeks for molars and the masseter muscle activity was recovered by 6th weeks in the experimental group. 2. The maximum bite force at normal side was recovered by 4th weeks for incisors, 6th weeks for canine, premolars and molars and the masseter muscle activity was recovered by 3rd weeks in the experimental group. 3. The method for internal fixation by 2.0mm miniplates at both superior and inferior border had no complications according for twenty patients and had a satisfactory recovery. According to the result, patient with mandibular angle fracture and subcondyle fracture, 8 weeks was required for bite force recovery. Therefore, patients with open reduction and internal fixation under general anesthesis, it can be assumed that 8 weeks was needed after operation in order to have normal bite force and masseter muscle recovery.

• Journal of Dental Rehabilitation and Applied Science
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• v.17 no.4
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• pp.245-256
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• 2001

The purpose of this study is to analyze the mechanical stress and displacement on the jaws during the simulated bilateral clenching task on the three-dimensional finite element model of the dentated skull with unilateral molar loss. For this study, the computed tomography(G.E.8800 Quick, USA) was used to scan the total length of human skull in the frontal plane at 2.0mm intervals. The fully assembled finite element model consists of the articular disc, maxilla, mandible, teeth, periodontal ligament and cranium. The FE model was used to simulate the bilateral clenching in intercuspal position. The loading condition was the force of the masseter muscle exerted on the mandible as reported by Korioth et al. degrees of freedom of the zygomatic region where the masseter muscle is attached were fixed as restraints. In order to reflect the actual action of the muscles force, the displacement of the region was attached where the muscle is connected to the temporal bone and restraint conditions were given values identical to values at the attachment region of the masticatory muscle but with the opposite direction of the reaction from when the muscle force is acted on the mandible. Although the mandible generally has higher displacement and von Mises stress than the maxilla, its mandibular corpus on the molar-loss side has a higher stress and displacement than the molar-presence side. Because the displacement and von Mises Stress was the highest on the lateral surface of mandibular corpus with molar loss, the stress level of the condyle on the molar-loss side is greater than that of the molar-presence side, which in turn caused the symphysis of the mandible to bend. In conclusion, the unilateral posterior bite collapse with molar loss under para-functional activities such as bruxism and clenching can affect the stress concentration on the condyle and mandibular corpus. It is therefore necessary to consider the biomechanical function of dento-skeleton under masticatory force while designing the occlusal scheme of restoration on alveolar bone with the posterior collapse.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.15 no.1
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• pp.13-20
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• 1985

The author obtained the oblique lateral trans cranial radiograms from 376 patients (114 of male, and 262 of female) with temporomandibular joint arthrosis. After tracing each film, the author analyzed the dimensional changes of the condylar heads with pain, clicking, mouth opening limitation, and masticatory difficulty respectively, which were the chief complaints of the TMJ arthrosis and compared these data with control group. The results were as follows; 1. There was a great predilection for occurrence of the TMJ arthrosis in female (262 cases) over male (114 cases). But there was no significant difference in ratio between the sexes on each symptom. In male, 60 patients (52.6%) had pain, 28 patients (24.6%) had clicking, 21 patients (18.4%) had mouth opening limitation, and 5 patients (4.4%) had masticatory difficulty. In female, 148 parients (56.5%) had pain, 57 patients (21.8%) had clicking, 47 patients (17.9%) had mouth opening limitation, and 10 patients (3.8%) had masticatory difficulty. 2. Examined controlled group, the author analyzed the dimension of W-W', 0-H, 0-A, 0-B on the right side first, and left side second. In male, the dimension of W-W' was 14.52㎜, 14.13㎜; 0-H was 13.92㎜, 13. 71㎜' 0-A was 8.91㎜, 9.0㎜ and 0-B was 8.67㎜, 8.78㎜. In female, W-W' was 13.77㎜, 13.51㎜; 0-H was 13.42㎜, 13.35㎜; 0-A was 8.92㎜, 9.01㎜; and 0-B was 8.59㎜, 8.80㎜. 3. W-W' and 0-H of the experimental group were distinctly lesser than the controlled group. Male with mouth opening limitation show the least (12.70㎜, 13.00㎜) on W-W', but both sexes with pain show the least on 0-H. There was no significant difference between experimental group with Clicking and controlled group on 0-H, 0-A, and 0-B. And also there was no difference on 0-B in patients with every symptom except masticatory difficulty. The dimensional changes of the condylar heads with those symptoms were as follows; a) In male patients, complaing of pain, W-W' of the right and left was 13.80㎜, 12.80㎜; 0-H was 13.10㎜, 12.90㎜; 0-A was 8.69㎜, 8.18㎜; 0-B was 8.33㎜, 8.42㎜. In female, W-W' was 13.01㎜, 12.90㎜; 0-H was 12.48㎜, 12.80㎜; 0-A was 8.60㎜, 8.49㎜; 0-B was 8.48㎜, 8.50㎜. b) In male patients with clicking, W-W' was 13.70㎜, 13.10㎜; 0-H was 13.90㎜, 13.10㎜; 0-A was 8.81㎜, 8.16㎜ 0-B was 8.34㎜, 8.25㎜. In female, W-W' was 13.10㎜, 13.50㎜; 0-H was 13.30㎜, 12.91㎜; 0-A was 8.95㎜, 8.49㎜; 0-B was 8.23㎜, 8.70㎜. c) In male patients with mouth opening limitation, W-W' was 12.70㎜, 13.00㎜; 0-H was 13.40㎜, 13.40㎜; 0-A was 8.37㎜, 8.48㎜; 0-B was 8.33㎜, 8.62㎜. In female, W-W' was 13.00㎜, 12.50㎜ 0-H was 12.90㎜, 13.10㎜; 0-A was 8.49㎜, 8.09㎜; 0-B was 8.77㎜, 8.01㎜. d) In male patients with masticatory difficulty, W-W' was 13.30㎜, 13.20㎜; 0-H was 13.40㎜, 12.60㎜; 0-A was 8.26㎜, 8.32㎜; 0-B was 7.80㎜, 8.20㎜. In female, W-W' was 12.30㎜, 12.00㎜; 0-H was 13.10㎜, 13.20㎜; 0-A was 8.68㎜, 7.95㎜; 0-B was 7.46㎜, 7.87㎜.