• 센서학회지
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• 제8권3호
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• pp.211-218
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• 1999

This paper describes the application of a coupled finite element-boundary element method (FE-BEM) to obtain the steady-state response of a piezoelectric transducer. The particular structure considered is a PZT4 disc-typed projector. The projector is three-dimensionally simulated to transduce applied electric charge on axial surfaces of the piezoelectric disc to acoustic pressure in air or in water. The directivity pattern of the acoustic field formed from the projected sound pressure is also simulated. And the displacement of the disc caused by the externally applied electric charge is shown in temporal motion. The coupled FE-BE method is described in detail.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제37권
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• pp.23.1-23.8
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• 2015

Background: The purpose of this study was to investigate the functional effects of temporalis myofascial flap after condylectomy, with or without disc removal, in elderly patients with anterior disc displacement (ADD) without reduction and an erosive condylar surface of the temporomandibular joint (TMJ). Methods: A total of 15 joints from 11 elderly patients (71-78 years old) were included. The patients had pain, mandibular dysfunction symptoms, and unilateral or bilateral ADD as well as an erosive condylar surface of the TMJ. All patients underwent temporalis myofascial flap reconstruction after condylectomy, with or without disc removal. If the maximal mouth opening (MMO) remained <35 mm after condylectomy, coronoidotomy was also performed. Self-assessed pain and mandibular function, including MMO and protrusive and lateral movements, were evaluated. Results: No patient experienced serious complications. Most measurements improved significantly after surgery compared to preoperatively. Most patients achieved nearly-normal mouth opening at 4 weeks after surgery. Although most patients felt discomfort during active postoperative physiotherapy, no patient reported serious pain during the follow-up period. Conclusion: Although nonsurgical therapy is often the first treatment choice for ADD without reduction of the TMJ, surgical intervention involving condylectomy and temporalis myofascial flap reconstruction may be a reasonable first option for elderly patients with an erosive condylar surface of the TMJ.

• Imaging Science in Dentistry
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• 제38권3호
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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.

• Coupled systems mechanics
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• 제1권2호
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• pp.165-182
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• 2012

Macroscopic hot spots formed due to the large thermal gradients at the surface of the disc brake rotor, make the rotor to fail or wear out early. Thermo-elastic deformation results in contact concentration, leading to the non uniform distribution of temperature making the disc susceptible to hot spot formation. The formation of one hot spot event will predispose the system to future hot spotting at the same location. This leads to the complete thermo-elastic instability in the disc brakes; multitude parameters are responsible for the thermo elastic instability. The predominant factor is the sliding velocity and above a certain sliding velocity the instability of the brake system occurs and hot spots is formed in the surface of the disc brake. Commercial finite element package ABAQUS(R) is used to find the temperature distribution and the result is validated using Rowson's analytical model. A coupled analysis methodology is evolved for the automotive disc brake from the transient thermo-elastic contact analysis. Temperature variation is studied under different sliding speeds within the operation range.

• 정보저장시스템학회논문집
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• 제6권2호
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• pp.57-62
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• 2010

This paper measured and analyzed the source of total power loss of an ODD of a notebook computer. It shows that the biggest power loss is the windage loss due to the friction between rotating disk and surrounding air. It measured the power loss by the tilting motion of a rotating disc which is originated from the unbalanced mass of the rotating disc or the squareness between case-rotor and shaft. The power loss of rotating disc due to tilting motion was also calculated by using FLUENT, and it was correlated with the measured one. This paper shows that the one of the effective methods to reduce the power loss of an ODD is to reduce the tilting motion of a rotating disc.

• Journal of Oral Medicine and Pain
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• 제43권4호
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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.

• Imaging Science in Dentistry
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• 제52권4호
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• pp.409-413
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• 2022

This report presents a rare case where a displaced temporomandibular joint (TMJ) disc was reduced to its normal position after orthognathic surgery, and long-term magnetic resonance imaging (MRI) follow-up visualized these postoperative changes. A 22-year-old male patient presented for facial asymmetry. He also complained of pain in the right TMJ area, and MRI showed disc displacements in both TMJs. After orthognathic surgery for facial asymmetry correction, the TMJ was re-evaluated. The symptom had resolved and the disc was positioned within the normal range during mouth opening. However, 6 and a half years after surgery, he complained of recurrent pain in the right joint, and MRI revealed medial disc displacement in the right TMJ. In conclusion, the influence of orthognathic surgery on the disc position might continue for a long time until the TMJ adapts to the new position. Careful and long-term follow-up is suggested to assess the TMJ complex.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제29권6호
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• pp.392-396
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• 2003

Purpose : The purpose of this study was to find the predictors for successful arthrocentesis for anterior disc displacement without reduction(ADD without Reduction) of the temporomandibular joint (TMJ). Patients and Methods : Arthrocentesis and lavage was carried out in 25TMJs of 22patients whose MRI findings were all anterior disc displacement without reduction. The effectiveness of the treatment was evaluated in terms of the postoperative range of maximal mouth opening (MMO) and the degree of postoperative pain score. Predectors which was analyzed were age, duration of painful locking, MMO, the degree of pain, perioperative clicking and the amounts of irrigation fluid. Results: 18cases (72%) was included to criteria for success. There were no significant differences in age, duration of locking, MMO and the degree of pain statistically. But In 15cases(83%) of successful cases, amouts of irrigated solution recovered to normal MMO were less than 150ml. And In 8cases (44%) of successful cases, perioperative clicking was appeared. Conclusion : Amounts of irrigated solution recovered to normal MMO and the appeareance of perioperative clkicking may be predictors of the successful results of arthrocenetesis of ADD without reduction of TMJ.

• Journal of Oral Medicine and Pain
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• 제41권2호
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• pp.41-47
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• 2016

Purpose: The purpose of this study was to analyze the size and morphology of mandibular condyle and mandibular fossa between temporomandibular joint (TMJ) disc displacement (DD) patients and healthy subjects using cone-beam computed tomography (CBCT). Methods: Twenty healthy subjects and twenty TMJ DD patients participated in this study respectively. We made five measurements in mandibular condyle (medio-lateral dimension, antero-posterior dimension, condyle height, intercondylar distance and intercondylar angle) and two measurements in mandibular fossa (mandibular fossa depth and articular eminence angle) using CBCT image. Results: There was no difference between two groups in medio-lateral dimension. In case of antero-posterior dimension, average of healthy controls was larger than that of TMJ DD patients, but that was not significant statistically. There were no significant differences between two groups in condyle height. Comparing intercondylar distance and intercondylar angle between two groups, there was no significant difference between two groups. In comparison of mandibular fossa depth and articular eminence angle, there was no significant difference between two groups. Conclusions: We couldn't find any definite relationship between TMJ morphology and TMJ DD.

• Journal of Oral Medicine and Pain
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• 제43권4호
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• pp.112-117
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• 2018

Purpose: The aim of this study is to compare the short-term effectiveness of hard and soft stabilizing appliances (H-A and S-A) in treating patients with acute temporomandibular joint (TMJ) disc displacement without reduction (DDwoR). Methods: Eighty one patients diagnosed as acute TMJ DDwoR at oral medicine of Chosun University Dental Hospital from November 2016 to September 2017 were included in this study. The subjects were divided into three groups: The control group (34 patients treated without occlusal appliance), the H-A group (31 patients treated with H-A) and the S-A group (16 patients treated with S-A). The pain intensity using Visual Analog Scale and maximum mouth opening (MMO) were evaluated every week for 8 weeks. Results: The improvement of the pain intensity and MMO in the H-A group and the S-A group compared with the control group were noted (p<0.05). Conclusions: This study suggests that hard and S-As may be equally useful in treating patients with TMJ DDwoR. S-A could be recommended to reduce the symptoms of TMJ DDwoR in short period.