• Imaging Science in Dentistry
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• v.31 no.3
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• pp.145-151
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• 2001

Purpose : To investigate the hypothesis that the morphology of the articular eminence of the temporomandibular joint is a predisposing factor for disc displacement. Materials and Methods: MR images of 126 temporomandibular joints in 94 patients were analyzed to assess for morphology of the articular eminence and disc displacement. The displaced disc was further categorized as disc displacement with reduction (DDWR) and disc displacement without reduction (DDWOR). The morphology of the articular eminence was classified into four types; box, sigmoid, flattened, and deformed. The relationship between the four types of shape of the articular eminence and the two types of disc position was assessed. Results: In the DDWR and DDWOR groups, the morphology of articular eminence were a box type in 40.5%, a sigmoid type in 30.2%, a flattened type in 24.6%, and a deformed type in 4.7%. The box type of the articular eminence were 34.3% in the DDWR group and 42.9% in the DDWOR group. The sigmoid type of the articular eminence were 34.3% in the DDWR group and 28.6% in the DDWOR group. The flattened type of the articular eminence were 28.6% in the DDWR group and 23.1 % in the DDWOR group. The deformed type of articular eminence were 2.9% in the DDWR group and 5.5% in the DDWOR group. Conclusion: Disc displacement is more likely to be found in the temporomandibular joints with a box-shaped articular eminence. It can be considered that shape of the articular eminence is related to the development of disc displacement.

• Advances in biomechanics and applications
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• v.1 no.3
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• pp.159-167
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• 2014

The aim of this study was to evaluate the influence of disc thickness on the normal behavior of the temporomandibular joint. Based on a specific patient case, CT scan images showing accentuated wear in the right disc were reconstructed and the geometrical and finite element model of the temporomandibular joint structures (cranium, mandible, articular cartilages and articular discs) was developed. The loads applied in this study were referent to the five most relevant muscular forces acting on the temporomandibular joint during daily tasks such as talking or eating. We observed that the left side structures of the temporomandibular joint (cranium, mandible and articular disc) were the most affected as a consequence of the wear on the opposite articular disc (right side). From these results, it was possible to evaluate the differences in the two sides of the joint and understand how a damaged articular disc influences the behavior of this joint and the possible consequences that can arise without treatment.

• The korean journal of orthodontics
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• v.24 no.2
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• pp.331-348
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• 1994

The purpose of this study was to investigate changes in the shape and ultrastructure of the articular disc of the rat mandibular joint with aging. Mechanical stress applied to the articular disc changes during neonatal, suckling, juvenile, adult and senile stages. Mandibular joints of 6 groups of rats(1-, 7-, 17-, 27-, 55-day and over-1-year groups) were removed en bloc and processed for light and electro microscopic study. The changes in the shape of articular disc were examined by light microscope in each group. Structural and ultrastructural changes in the articular disc were examined by light and electron microscope in each group. The results were as follows : In the 1-day and 7-day groups, the articular disc was long and slender in shape and the articular disc was not fitted with the shape of the mandibular fossa and condyle. However' after that time, the anterior and posterior portions of the articular disc were more bulged and the middle portion was shorter and biconcave. Thus the articular disc was well fitted with the shape of the mandibular fossa and condyle. The cell density decreased with aging. In the l -day and 7-day groups, the Golgi apparatus, rough endoplasmic reticulum and free ribosome, which are involved in the synthesis of intracellular and extracellular matrix, were developed. In the 17-day, 27-day and 55-day groups, not only the cell organelles involved in the synthesis of the intracellular and extracellular matrix but also the cell organelles involved in the remodeling of the extracellular matrix(i.e., finger-like cell process, lysosome and mitochondria)were well developed. With advancing age, intracytoplasmic microfilaments were more accumulated and condroid cells increased. In the over-1-year group, the majority of cells of the articular disc were chondroid cells. The majority of cytoplasmic compartment were filled with intracytoplasmic microfilaments and cell organelles were not developed. Therefore, metabolic activities of the cell was markedly reduced and cells contained structures enduring mechanical stress, and cells which were in the process of degeneration were observed occasionally.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.25 no.2
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• pp.319-330
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• 1995

This study was designed to evaluate the interrelationship between the condylar head position in transcranial view and the articular disc position in the arthrography. The condylar positions were assessed by subjective method and linear measurement method on the transcranial view. The subjects for this study consisted of 24 symptomatic joints with normal disc position, 37 joints with anterior disc displacement with reduction and 44 joints with anterior disc displacement without reduction that were classified by arthrotomography under the fluoroscopic guidance. The interrelationship between the condylar head position in transcranial view and the articular disc position in the arthrography was evaluated by Chi square test. The obtained results were as follows : 1. There was no significant interrelationship between the position of condylar head in closed mouth state on transcraniaJ view and articular disc position in the arthrography (p>0.05). 2. There was no significant interrelationship between the changes of interarticular distance in 1 inch opening state and articular disc position in the arthrography (p>0.05). 3. There was no significant interrelationship between the position of condylar head related to the apex of articular eminence in 1 inch opening state and articular disc position in the arthrography(p>0.05). 4. There was significant interrelationship between the changes of interarticular distance that is assessed by linear measurement method in maximum opening state and articular disc position in the arthrography(p<0.05), but there was no significant interrelationship when the condylar head position was assessed by subjective method(p>0.05). 5. There was significant interrelationship between the degree of condylar translation in maximum opening state and articular disc position in the arthrography(p<0.05). 6. The correlation coefficient between two methods to assess the position of condylar head were 0.7989: the condylar head position in articular fossa in closed state, 0.6847: interarticular space in 1 inch opening state, 0.8965: the degree of condylar translation in 1 inch opening state, 0.5944: the changes of interarticular space in maximum opening state, 0.9215: the degree of condylar translation in maximum opening state.

• Journal of Oral Medicine and Pain
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• v.44 no.4
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• pp.189-194
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• 2019

Perforation of articular disc of temporomandibular joint is a unusual condition and diagnosed through magnetic resonance imaging (MRI), arthrography or arthroscopic surgery. We attempted to investigate the suspicious findings of articular disc perforation through examination commonly used in temporomandibular disorder (TMD) patients. We retrospectively analyzed the clinical and imaging findings of five TMD patients whose articular discs were perforated based on MRI. The most meaningful finding was the abnormal width of the joint space in cone-beam computed tomography. Thus, the clinician should perform a thorough assessment of the joint space in TMD patients and conduct additional investigation to determine what caused the abnormal joint space.

• The Journal of the Korean dental association
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• v.58 no.6
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• pp.364-376
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• 2020

Internal derangement of the temporomandibular joint (TMJ) is condition in which articular disc has become displaced from its normal functional relationship with the mandibular condyle and the articular portion of the temporal bone. Common types of internal derangement include disc displacement with reduction (with or without intermittent locking), and disc displacement without reduction (with or without limited opening) classified according to the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD). Treatment varies depending on diagnosis. Therefore, differential diagnosis should be made for appropriate treatment.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.26 no.2
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• pp.191-196
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• 2000

Purpose This study is to report presurgical magnetic resonance imaging(MRI) findings of the temporomandibular joint which had perforation in the disc or its surrounding tissues and to improve its diagnostic rate using MRI. Patients and Methods The sample consisted of patients who visited the TMJ clinic at Yongdong Severance Hospital, Yonsei University, during the years, 1992 and 1997. They were diagnosed as TMJ internal derangement and received surgical treatment. We divided them into two groups. The first group comprised of 85 joints with perforated disc or its surrounding tissues and which were confirmed surgically. The second group of 62 joints which only had disc displacement without perforation, hyperemia or adhesion served as control. Results The preoperative diagnostic sensitivity of TMJ perforation using MRI was 74.1%. The MRI findings for diagnosis of the TMJ perforation were degenerative change of the condyle head or the articular fossa, bone to bone contact between the condyle head and the articular eminence or the articular fossa, bony spurring or osteophytosis of the condyle head, flattening of articular surface of the condyle head or the articular eminence, discontinuity of the disc and the arthrographic effect due to joint effusion. Conclusion The preoperative diagnostic sensitivity of TMJ perforation using MRI in this study was 74.1% which was lower than the diagnostic rate using the arthrogram. Further investigations are needed to improve the diagnostic accuracy of TMJ perforation using MRI.

• Imaging Science in Dentistry
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• v.38 no.3
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• pp.153-161
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• 2008

Purpose : To compare and evaluate the diagnostic ability of cone beam computed tomography (CBCT) and magnetic resonance imaging (MRI) of the temporomandibular joint (TMJ). Materials and Methods : CBCT and MRI of 46 TMJs of 23 patients with TMJ disorders were evaluated. They were divided into 3 groups according to the position of the articular disc of the TMJ at closed mouth position and the reduction of the disc during open mouth position on MRI: no disc displacement group (NDD), disc displacement with reduction group (DDR), and disc displacement without reduction group (DDWR). With PACS viewing soft-wares, position of mandibular condyle in the articular fossa, osseous change of mandibular condyle, shape of articular fossa, and mediolateral and anteroposterior dimensions of mandibular condyle were evaluated on CBCT and MRI. Each value was tested statistically. Results : The position of mandibular condyle in the articular fossa were concentric in the NDD, DDR, and DDWR of CBCT and NDD of MRI. However, condyle was positioned posteriorly in DDR and DDWR of MRI. Flattening, sclerosis and osteophyte of the mandibular condyle were much more apparent on DDR of CBCT than MRI. And the erosion of the condyle was much more apparent on DDWR of MRI than CBCT. Box and Sigmoid types of articular fossa were found most frequently in DDR of MRI. Flattened type was found most frequently in DDR of CBCT and deformed type was found most frequently in DDWR of CBCT. No significant difference in mediolateral and anteroposterior dimensions were shown on CBCT and MRI. Conclusion : Since MRI and CBCT has unique diagnostic imaging ability, both modalities should be used together to supplement each other to evaluate TMJ.

• The Journal of Korean Academy of Prosthodontics
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• v.37 no.1
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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.

• Journal of Oral Medicine and Pain
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• v.43 no.4
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• pp.142-146
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• 2018

Patients with temporomandibular disorder often present with acute occlusal change and properly managed with conservative treatment. If such change is caused by unusual etiology, differential diagnosis may be challenged. This article describes the diagnosis of a patient exhibiting pain and acute posterior open bite on the ipsilateral side after chewing hard food. After initial conservative treatment failed to resolve the complaint, magnetic resonance imaging was ordered and confirmed partial perforation of articular disc. Disc perforation itself is usually chronic in nature, but sudden macrotrauma may also cause the disorder. However, occlusal discrepancy caused by disc perforation is rare and seldom reported. We present a case of acute malocclusion caused by disc perforation with a review of related literature.