• 대한치과보철학회지
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• 제37권1호
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• pp.71-92
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• 1999

This study is to analyze the stress and displacement on the jaws during the bilateral and unilateral clenching task on three dimensional finite element model of the dentated skull. 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 1.9mm intervals. The CAD data were extracted from the tomograms through digitizer(Summa Sketch III, USA) and then reconstructed by means of the spline method in the CAD program. In this project, a commercial software I-DEAS(Master Series ver-sion 3.0, SDRC Inc, USA) was used for three-dimensional stress analysis on the finite element model. which consists of articular disc, maxilla, mandible, teeth, periodontal ligament and cranium. The results are as follows. ; 1. During the bilateral clenching, each major muscle forces caused high stresses on various areas of skull: masseter muscle on articular disc and teeth ; temporal muscle on mandible and periodontal ligament ; medial pterygoid muscle on the temporomandibular joint. During the unilateral clenching, masseter muscle induced the maximum stress ; medial pterygoid muscle the minimum stress. 2. During the bilateral clenching, higher compressive stresses on articular disc were generated by the masseter muscle and higher deformation occurred on the most front outer sites. And during the unilateral clenching, temporal muscle and medial pterygoid muscle exerted their forces to twist temporomandibular joint area of the balancing side and induced a higher compressive stresses on the front outer sites of articular disc. 3. During the bilateral clenching, the masseter muscle bended the mandible outwardly, and then caused tensile stresses on the lingual surface of mandibular symphysis. And the medial pterygoid muscle caused tensile stresses on the labial surface of mandibular symphysis. 4. When each muscles were simultaneously applied on jaws, a high stress and displacement took place on mandible rather than on the maxilla. Also, a high stress and displacement took place during the unilateral clenching rather than during the bilateral clenching.

• 대한치과보철학회지
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• 제28권2호
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• pp.175-182
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• 1990

This study was performed to investigate the influence of occlusal change on the masticatory muscle activity. 8 students without any symptom of T.M.J. dysfunction, any history of prosthodontic or orthodontic treatment on dental college of WonKwang Univ. were participated in this study. The activity of masseter and anterior temporal muscles were measured by bioelectric processor(EM2, Myotronics, Inc., U.S.A.) during voluntary maximal clenching on natural teeth, by splint with bilateral posterior surface contact, by splint with unilateral posterior surface contact, and by splint without unilateral posterior teeth contact. The obtained results were as follows ; 1. The loss of posterior contact on noe side resulted in change of the activity of anterior temporal and masseter muscle during clenching on ipsilateral side, but there was no change of muscle activity on contralateral side. 2. The activity of anterior temporal and masseter muscle during clenching were not affected by the pattern of occlusal contact. 3. There were no difference between the activity of anterior temporal and masseter miuscle during clenching by natural teeth and by occlusal splint.

• 대한치과보철학회지
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• 제35권3호
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• pp.517-534
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• 1997

It has been held that excessive mechanical forces to the osseous and soft tissues of the TMJ result in joint dysfunction. Understanding the stress pattern on TMJ is very important in TMJ research. But, it is very difficult to measure directly the biomechanical stress distribution in the TMJ when the mandible is loaded. Therefore, stress distribution in the TMJ during functional movement was studied through animal experiment or mathematical model. It was observed and compared the stress distribution occuring in the working and balancing condyle when lower right canine, lower right first molar and lower right second molar were clenched by the three dimensional finite element analysis. Also, stress distribution in the working and balancing condyles were observed and compared when $20^{\circ}$ forward and buccal bite forces were applied to the first molar. The results were as follows : 1. Stress distribution in the condyles during unilateral clenching of the first molar, second molar, canine showed no difference. In the working condyle, tensile force was concentrated on the lateral aspect of the condylar articular surface and condylar neck. And compressive force was concentrated on the anteromedial and lateral aspect of condyle. In the balancing condyle, tensile and compressive forces were concentrated on the lateral aspect of the condylar articular surface and stress transmission to the temporal bone was not observed. 2. When lateral forces were applied to the first molar, tensile forces were concentrated on the medial aspect of the condylar neck and condylar posterior surface in working and balancing condyle. Compressive force was concentrated on the anteromedial and lateral surface of the condyle and stress transmission to the temporal bone was not observed. 3. During unilateral clenching, stress in the working condyle decreased as the occlusal load moved posteriorly while the stress in the balancing condyle increased. when lateral force was applied to first molar, the incremental amount of stress was greater than vertical load. 4. During unilateral clenching, the average balancing/working condyle stress ratio was 2.52. There was a greater concentration of stress in the balancing condyle. The ratio increased as the occlusal load moved posteriorly and decreased considerably when lateral forces were applied to the first molar.

• 대한치과보철학회지
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• 제40권6호
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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.

• 구강회복응용과학지
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• 제17권4호
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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 Oral Medicine and Pain
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• 제12권1호
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• pp.53-61
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• 1987

In order to evaluate the effect of unilateral tooth clenching, the author observed a feature of producing the symptom complex related to pain and discomfort by the isometric unilateral canine biting under force of 5kg(FS) in Korean 31 adult females within normal masticatory function who were divided into the bilateral, the right and the left group according to their habitual sides of mastication, and analyzed the observed data statistically. The obtained results were as follows: 1. The duration of the isometric unilateral canine biting maintained before the occurrence of symptom complex related to pain and discomfort 66.72 seconds at right side and 39.50 seconds at left side in a group of subjects with bilateral habitual mastication. And the difference of the duration between of unilateral biting side was almost significant (P<0.05). 2. The most frequent region of occurrence of symptom complex related to pain and discomfort by the isometric unilateral canine biting was the contralateral superficial masseter muscle in a group of subjects with bilateral habitual mastication.

• Journal of Oral Medicine and Pain
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• 제33권1호
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• pp.85-95
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• 2008

구강안면통증의 주원인의 하나인 측두하악장애는 다양한 기여요인에 의해 발생하거나 악화되는데, 특히 이갈이, 이악물기 등의 비기능적 구강악습관은 중요한 기여요인으로 고려된다. 구강악습관과 저작근의 관련성에 대해서는 근전도 등을 이용한 연구가 이루어져왔으나, 안면표정근에 미치는 영향에 대해서는 연구된 바가 거의 없다. 그러므로 본 연구는 근육의 탄성도과 경직도를 정량적으로 평가할 수 있는 촉각센서(tactile sensor)를 이용하여 구강악습관이 저작근과 안면표정근에 미치는 영향을 평가하고자 하였다. 건강하고 건전한 치열을 가지고 있으며 Class I 교합관계의 정상골격인 지원자10명(20대 남성)을 연구대상으로 선택하여 촉각센서(Venustron II, Axiom Co, 일본)를 이용하여 이완 상태와 편측 이악물기(피검자가 선호하는 측의 제1대구치 부위에서 교합측정기를 50Kg force의 힘으로 깨문 상태), 턱내밀기(전치 상하절단연이 만나는 위치까지 턱을 내민 상태), 입술힘주기(치아는 닿지 않는 상태에서 입술만 꼭 다문 상태) 상태에서 저작근과 안면표정근의 경직도와 탄성도를 측정하였다. 측정근육은 측두근 전부, 교근(이상 저작근), 전두근, 하안륜근, 대관골근, 상 하 구륜근, 이근(이상 안면표정근)이었다. 통계처리를 위해 paired t-test, correlation coefficients, ANOVA 및 multiple comparison t-tests을 사용하였다. 편측 이악물기를 할 때 측정한 모든 근육에서 경직도와 탄성도는 좌우 차이를 보이지 않고 높은 상관관계를 보였다. 교근은 편측 이악물기 뿐만 아니라 턱내밀기, 입술힘주기의 시행된 모든 구강악습관에 의해 경직도가 증가하고 탄성도는 감소하였다(p<0.05). 측두근과 대관골근은 편측 이악물기의 영향을 받았으며, 상 하구륜근 및 이근의 경직도와 탄성도는 입술힘주기에 의해 크게 변화하였다(p<0.05). 본 연구의 결과는 편측 이악물기, 턱내밀기, 입술힘주기 같은 구강악습관은 저작근뿐만 아니라 안면표정근, 특히 구강주위근육에도 영향을 준다는 것을 보여준다.

• 대한치과의사협회지
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• 제15권3호
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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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• 제38권2호
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• pp.175-185
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• 2013

측두하악장애를 주소로 하는 환자 276명에 대해 임상검사와 방사선검사를 시행하였다. 하악과두 저형성으로 진단된 189명의 실험군과 골관절염으로 진단된 87명의 대조군을 임상적으로 비교하여 다음과 같은 결과를 얻었다. 1. 하악 과두저형성은 골관절염과 임상적으로 많은 부분이 유사하였다. 2. 하악 과두저형성은 골관절염에 비하여 방사선적 진단부위와 통증부위의 일치율이 현저하게 낮았다. 3. 하악 과두저형성 양측이환군이 편측이환군에 비해 교합불편감 및 이악물기습관이 많았다. 4. 편측이환군 비교시 하악 과두저형성은 편측저작습관이 높았으며, 개구제한감을 더 많이 느꼈다. 골관절염은 아침의 불편감 및 두통을 많이 호소하였으며 진단부위와 단순관절음 일치율이 높았다. 5. 양측이환군 비교시 하악 과두저형성이 골관절염보다 평상시 두통을 더 많이 호소하였으며, 수평피개량도 컸다.

• 구강회복응용과학지
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• 제17권2호
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• pp.75-84
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• 2001

The purpose of this study is to to analyze the mechanical stress on articular disk of the dentated skull with the condition of unilateral posterior molar missing. For this study, the three dimensional finite element model of human skull scanned by means of computed tomography. (G.E. 8800 Quick, USA) was constructed. The finite element model of jaws is composed of 98,394 elements and 38,321 nodes, and it consists of articular disc, maxilla, mandible, teeth, periodontal ligament and cranium. Boundary condition included rigid restraints at the first molar and endosteal cortical surfaces of the insertion points of temporal bone. The data derived from Nelson's study were used for the loading conditions of mandible during clenchings and for maxilla, new loading and constraint conditions were applied. A clenching task during intercuspal position was modeled to the three dimensional finite element model. The stress level and displacement of articualr disc on the model with unilateral posterior molar missing under bilateral clenching task can be analyzed. During bilateral clenchings, the compressive stress level and diplacement of the articular disk on the side of unilateral posterior molar missing is greater than that on the case with full dentition, whereas a higher stress was found on the disk on the balancing side of the full dentition. Although this kind of study is not enough to explain the role of occlusion as an etiologic factor of TMD, there may be a possibiliy that the condition of posterior molar missings may contribute in part to the TMJ biomechanics.