• Journal of Oral Medicine and Pain
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• 제16권1호
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• pp.33-72
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• 1991

The purpose of this study was to investigate the stress distribution and the displacement in the temporomandibular joints following the teeth loss patterns. The three dimensional finite element method was used for a mathematical model. The finite element model was composed of 1,632 elements and 2,411 nodes in the mandible with articular disc and mandibular fossa of the temporal bone. The masseter, the temporal and the internal pterygoid muscle forces were applied at each insertion site, bisecting point of gonion and antegonion, tip of the coronoid process, and gonion at the ration of 2:2:1 respectively. The directions of muscles force were obtained from frontal and lateral cephalometric tracings using bony landmarks of the skull. The results were as follows : 1. In control model, the minimum principal stresses were concentrated on the region of anterosuperior part of the condyle head and articular disc, and maximum principal stresses on the anterior part of the condyle head and posterolateral part of the articular disc. 2. In case of unilateral teeth loss, the greater principal stress appeared at the teeth loss side and the principal stresses increased at the teeth loss side as the number of the posterior teeth loss went up. 3. In case of bilateral teeth loss, the principal stresses were greater than those of the control model and as the number of the posterior teeth loss increased, the grater principal stresses on the temporomandibular joints appeared at the both side. 4. When the posterior teeth existed bilateral, the principal stress patterns were similar to those of the control model. 5. The displacement ws directed mainly upward and backward in the upper part of the temporomandibular joints and upward and forward in the largest part of the condyle head. The displacement increased as the number of the posterior teeth loss went up.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.1266-1271
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• 2007

General coil spring has linearity. However, disc spring has non-linearity so that using this non-linearity disc spring can be designed to do shock-absorbing in cases we need because shock response also has non-linearity. By changing the shape and stacking number, it is satisfactory with response of displacement, velocity and acceleration. Conventionally, disc spring was used to control the vibration against huge load and limited space. However, it is limitedly used because of difficulty of the designing guidance. Therefore, disc spring is needed to study further in order to apply it widely. Response of disc spring is compared to response of coil spring by changing ho/t radio with computer simulation and the usage of disc spring is increased through analysis of effect of design factors. The purpose of this paper is that the shock response of disc spring is calculated through numerical simulation and effect of ho/t and stiffness is analyzed to broad usage so that design factor of disc spring is presented.

• 한국소음진동공학회논문집
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• 제18권2호
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• pp.153-159
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• 2008

General coil spring has linearity. However, disc spring has non-linearity so that using this non-linearity disc spring can be designed to do shock-absorbing in cases we need because shock response also has non-linearity. By changing the shape and stacking number, it is satisfactory with response of displacement, velocity and acceleration. Conventionally, disc spring was used to control the vibration against huge load and limited space. However, it is limitedly used because of difficulty of the designing guidance. Therefore, disc spring is needed to study further in order to apply it widely. Response of disc spring is compared to response of coil spring by changing $h_o/t$ ratio with computer simulation and the usage of disc spring is increased through analysis of effect of design factors. The purpose of this paper is that the shock response of disc spring is calculated through numerical simulation and effect of $h_o/t$ and stiffness is analyzed to broad usage so that design factor of disc spring is presented.

• Journal of Oral Medicine and Pain
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• 제43권4호
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• pp.125-130
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• 2018

Purpose: The etiology of temporomandibular disorders (TMDs) is complex and multifactorial including trauma, anatomical, pathophysiological, social and psychological factors. Psychological factors can induce or sustain TMDs in various ways. And psychological problems, such as anxiety and depression can be occurred due to TMDs. Therefore, evaluation of psychological factors in patients with TMDs is important. Although disc displacement (DD) is crucial in clinical situation, most of studies have focused on the relationship of psychosocial factors and myofascial pain. And also, Subtypes of DD can cause different degrees of discomfort, it is necessary to evaluate the psychological states of the patients according to the subtype. The Hospital Anxiety Depression Scale (HADS) is one of the self-report questionnaire to evaluate the psychological factors. HADS-Anxiety (HADS-A) and HADS-Depression (HADS-D) are assessed through 14 questions. The purpose of this study was to evaluate anxiety and depression assessed by HADS in patients diagnosed with subtypes of DD according to diagnostic criteria for TMDs. Methods: Four hundred thirty nine patients were diagnosed as one of the subtypes of DD. One hundred fourty nine subjects with no symptoms were set as control groups. All of them answered the HADS for Koreans. The cut-off score for anxiety and depression was set a score of 8. The chi-square test was performed to evaluate association between DD and anxiety/depression. Results: There was a significant difference in HADS-D between five groups (p<0.01). However, there was no significant difference in HADS-A. All the DD groups showed a significant difference in HADS-D compared with the control group except the DD without reduction without limited opening group. The DD without reduction with limited opening group showed the highest rates in HADS-D (40.4%). Conclusions: Based on the above results, it is necessary to consider the depression in treatment of the patients with DDs.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.454-457
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• 1995

In optical disc system, tracking actuator is consisted of coarse actuator and fine tracking actuator. This, two-stage actuator, requires many devices and two servos for large stroke and precisional displacement. These complicate configuration increases moving mass. So dynamic characteristics become bad, that is, sensitivity of high frequency gain decrease. In this paper, frequency performance is willing to be better as so one dimensional tracking actuator is designed. In order to investigate the performance of the proposed tracking actuator, the Bode diagram is plotted with Dynamic analyzer and friction characteristic is explained. Finally, tracking error performance is ins investigated into 0.1 .mu.m resolution with MATLAB simulation.

• 한국공간구조학회논문집
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• 제23권4호
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• pp.89-96
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• 2023

The seismic retrofits of existing structures have been focused on the control of structural responses which can be achieved by providing displacement capacity through inelastic ductile action at supplemental devices. Due to their hysteretic characteristics, it is expected to sustain damage through repeated inelastic behaviors including residual deformation which might increase repair costs. To solve such drawbacks of existing yielding devices, this study proposes a self-centering disc spring brace that sustains large axial deformation without structural damage while providing stable energy dissipation capacity. The hysteretic behaviors of suggested brace are first investigated based on the quasi-static cyclic test procedure. Experimental results present the effective self-centering behavior and an analytical model is then suggested in order to reasonably capture the flag-shaped hysteretic behavior of the disc spring brace.

• Journal of Korean Neurosurgical Society
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• 제46권2호
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• pp.144-151
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• 2009

Objective: To compare two testing protocols for evaluating range of motion (ROM) changes in the preloaded cadaveric spines implanted with a mobile core type Charite$^{TM}$ lumbar artificial disc. Methods: Using five human cadaveric lumbosacral spines (L2-S2), baseline ROMs were measured with a bending moment of 8 Nm for all motion modes (flexion/extension, lateral bending, and axial rotation) in intact spine. The ROM was tracked using a video-based motion-capturing system. After the Charite$^{TM}$ disc was implanted at the L4-L5 level, the measurement was repeated using two different methods: 1) loading up to 8 Nm with the compressive follower preload as in testing the intact spine (Load control protocol), 2) loading in displacement control until the total ROM of L2-S2 matches that when the intact spine was loaded under load control (Hybrid protocol). The comparison between the data of each protocol was performed. Results: The ROMs of the L4-L5 arthroplasty level were increased in all test modalities (p < 0.05 in bending and rotation) under both load and hybrid protocols. At the adjacent segments, the ROMs were increased in all modes except flexion under load control protocol. Under hybrid protocol, the adjacent segments demonstrated decreased ROMs in all modalities except extension at the inferior segment. Statistical significance between load and hybrid protocols was observed during bending and rotation at the operative and adjacent levels (p< 0.05). Conclusion: In hybrid protocol, the Charite$^{TM}$ disc provided a relatively better restoration of ROM, than in the load control protocol, reproducing clinical observations in terms of motion following surgery.

• Journal of Acupuncture Research
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• 제37권3호
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• pp.177-180
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• 2020

Background: The aim of this study was to examine whether the effects of acupotomy therapy were beneficial for the treatment of protrusion of lumbar intervertebral disc. Methods: The number of patients (n = 80) were equally assigned into treatment group and control group. Treatment group was given acupotomy therapy twice a week, and control group was given acupuncture 3 times a week, for 4 weeks. The beneficial effect and changes in score of the Japan Orthopedic Association (JOA) for low back pain were observed. Results: Among 40 cases in the treatment group, there were 25 (62.5%) with an excellent effect, 13 (32.5%) with good effect, 1 (2.5%) with a medium effect and 1 (2.5%) with poor effect, with the total experiencing an excellent/good effect of 95.0%. Among 40 cases in the control group, there were 11 (27.5%) with an excellent effect, 17 (42.5%) with good effect, 10 (25.0%) with a medium effect, and 2 (5.0%) with poor effect, with an excellent/good rate of 70.0%. The result of the rank sum test showed Z = -4.923, p < 0.05 in the comparison, indicating a significantly better outcome following acupotomy compared with acupuncture. JOA scores increased in both groups after treatment (p < 0.05), which was more significant in the acupotomy treatment group (p < 0.05). Conclusion: Acupotomy therapy has a beneficial effect on protrusion of lumbar intervertebral disc.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제26권2호
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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.

• Physical Therapy Rehabilitation Science
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• 제12권2호
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• pp.92-104
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• 2023

Objective: The purpose of this study was to investigate the effect of spinal mobilization with leg movement (SMWLM) and neural mobilization (NM) in patients with lumbar disc herniation (LDH) accompanied by radiating pain. Design: Three-group pre-test-post-test control group design. Methods: We enrolled 48 participants, whom we randomly assigned to three groups. The SMWLM group (n=16) underwent 20 min of conventional physical therapy (CT) and 20 min of SMWLM. The NM group (n=16) underwent 20 min of CT and 20 min of NM. The control group (n=16) underwent 20 min of CT. These interventions in all the groups were performed three times a week for 4 weeks. Numeric pain rating score (NPRS), body grid chart score (BGCS), passive straight leg raise (PSLR), active lumbar flexion range of motion (ALFROM), korean version oswestry disability index (KODI), and korean version fear avoidance beliefs questionnaire (KFABQ) were measured pre- and post-intervention. Results: In all three groups, the NPRS, PSLR, KODI, and KFABQ scores were significantly different pre- and post-intervention (p<0.05). Significant differences were observed in BGCS and ALFROM in the SMWLM and NM groups pre- and post-intervention (p<0.05). The SMWLM group showed more improvement in the NPRS of leg pain, ALFROM, and KFABQ score than that exhibited by the NM and control groups (p<0.05). Conclusions: Both SMWLM and NM were effective for improving back and leg pain, centralization of symptoms, mechanical sensitivity, lumbar mobility, lumbar functional disability, and psychosocial functioning in patients with LDH with radiating pain.