• The Journal of the Korean dental association
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• v.37 no.6 s.361
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• pp.445-455
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• 1999

Arthrocentesis is a simple, less invasive, inexpensive, and highly efficient procedure for closed lock of the temporomandibular joint with regard to the lack of recurrence of symptoms during extended periods of follow-up and significiant improvement in pain and jaw function. It can be performed under local anesthesia. Arthrocentesis closed lock provide sustained normal joint function and marked pain relief. This study is the clinical outcome of arthrocentesis for closed lock of the temporomandibular joint. 160 patients(169 joints) who had experienced sudden-onset, persistent limited mouth opening were the subjects of this study. Arthrocentesis of the upper compartment of the affected TMJ was performed using normal saline. As results, at 3-60 months postarthrocentesis maximum mouth opening(MMO) had increased from mean of 27.7mm to 43.5mm, contralateral movements(CLM) from mean 5.74mm to 9.55mm, midline deviation during mouth opening from mean 3.04mm to 0.69mm. In 130 cases there was a history of joint noises, in 52 cases all noise had ceased after procedures.

• Journal of The Korean Society of Integrative Medicine
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• v.6 no.1
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• pp.25-33
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• 2018

Purpose : The present study aimed to investigate the of the based on their oral health status and the study findings will provide the basic data for establishing future oral health related policies for the elderly. Methods : A total of 50 elderly participants were selected for the study. Oral examinations were performed by a single trained dental hygienist, the oral health status was classified according to the use of dentures, presence of temporo-mandibular joint (TMJ) noise, presence of TMJ pain, presence of trismus, presence of preferred chewing, and number of residual teeth. An oral health-related survey using the in-person interview method was conducted by two dental hygienists and 30 types of foods were selected for the assessment of chewing ability. For data analysis, the Mann-Whitney U test and Spearman's Rho analysis were performed to investigate the association between oral health status and chewing ability. Result : The results of the present study revealed that there was a statistically significant positive (+) correlation between the number of residual teeth and chewing abilities. In other words, as the number of residual teeth increased, chewing ability increased as well, with the differences being statistically significant. Conclusion : Improvement of oral health in the elderly is a fundamental aspect of healthy aging. Therefore, the implementation of more efficient oral health care policies for the elderly is required as We move toward a super-aged society.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.49 no.1
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• pp.29-38
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• 2012

The noise generated in the process of obtaining the medical image acts as the element obstructing the image interpretation and diagnosis. To restore the true image from the image polluted from the noise, the total variation optimization algorithm was proposed by the R.O. F (L.Rudin, S Osher, E. Fatemi). This method removes the noise by fitting the balance of the regularity and fidelity. However, the blurring phenomenon of the border area generated in the process of performing the iterative operation cannot be avoided. In this paper, we propose the adaptive total variation method by mapping the control parameter to the proposed transfer function for minimizing boundary error. The proposed transfer function is determined by the noise variance and the local property of the image. The proposed method was applied to 464 tooth images. To evaluate proposed method performance, PSNR which is a indicator of signal and noise's signal power ratio was used. The experimental results show that the proposed method has better performance than other methods.

• Imaging Science in Dentistry
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• v.50 no.1
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• pp.1-7
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• 2020

Purpose: This study was performed to evaluate the magnitude of artifacts produced by gutta-percha and metal posts on cone-beam computed tomography (CBCT) scans obtained with different tube currents and with or without metal artifact reduction (MAR). Materials and Methods: A tooth was inserted in a dry human mandible socket, and CBCT scans were acquired after root canal instrumentation, root canal filling, and metal post placement with various tube currents with and without MAR activation. The artifact magnitude was assessed by the standard deviation (SD) of gray values and the contrast-to-noise ratio (CNR) at the various distances from the tooth. Data were compared using multi-way analysis of variance. Results: At all distances, a current of 4 mA was associated with a higher SD and a lower CNR than 8 mA or 10 mA (P<0.05). For the metal posts without MAR, the artifact magnitude as assessed by SD was greatest at 1.5 cm or less (P<0.05). When MAR was applied, SD values for distances 1.5 cm or closer to the tooth were reduced (P<0.05). MAR usage did not influence the magnitude of artifacts in the control and gutta-percha groups(P>0.05). Conclusion: Increasing the tube current from 4 mA to 8 mA may reduce the magnitude of artifacts from metal posts. The magnitude of artifacts arising from metal posts was significantly higher at distances of 1.5 cm or less than at greater distances. MAR usage improved image quality near the metal post, but had no significant influence farther than 1.5 cm from the tooth.

• Journal of dental hygiene science
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• v.9 no.1
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• pp.9-15
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• 2009

Aimed at office workers at their height of Temporomandibular joint disorder(TMD), organized self-filling questionnaires were distributed from January 7 to 26, 2008 to 216 workers in the fields of service, office work, and production in D metropolitan city, to get a proper recognition about prevention and treatment of TMD by observing how strongly occupational stress influence on them. The findings of the study were as follows: 1. For subjective symptoms of joint noise as TMD, occasional was 45.8% and often 12.0%, while for joint dislocation often was 12.0%. 41.2% said they feel pains while chewing, while 24.1% said they occasionally feel pains while not chewing. 2.8% said they often experience mouth-opening disorder. 2. For joint noise, answers were significantly different according to their ages, while 30's are at their height (P < 0.05). For joint dislocation, the shorter they worked the more they have it, so less than a year worker was 37.9%, while less than 3 years 31.0%, and less than 5 years 20.7%. For work type, daytime workers have more dislocation, 58.6%, than shift-workers 34.5% (P < 0.05, P < 0.01). For pains while chewing, the shorter they worked, the more they experienced, which is the same as mouth-opening disorder (P < 0.01). 3. Workers with mouth-opening disorder have much stress on occupational autonomy (P < 0.05) and workers with dislocation and pains while chewing have much stress on relation trouble (P < 0.05, P < 0.01). Workers with highly occupational insecurity has much trouble on dislocation and pains while chewing, while workers with dislocation have significantly much stress on unproper compensation (P < 0.05). 4. For who have joint dislocation, they have much stress on relation-trouble, occupational disorder, and un-proper compensation (P < 0.01, P < 0.05). Workers with pains while not chewing showed significant difference about occupational insecurity and relation troubles (P < 0.05, P < 0.01). Who have mouth-opening disorder showed significant difference about occupational autonomy (P < 0.05).

• Maxillofacial Plastic and Reconstructive Surgery
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• v.23 no.1
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• pp.48-58
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• 2001

After performing mandibular setback surgery, we found some changes in patterns and organs of speech. This investigation was undertaken to investigate the aspect and degree of speech patterns according to the amount of surgical setback in mandibular prognathic patients. Thirteen patients with skeletal Class III malocclusion were studied preoperative and postoperative over 6 months. They had undergone the mandible setback operation via bilateral sagittal split ramus osteotomy(BSSRO). We split the patients into two groups. Group 1 included patients whose degree of mandibular setback was 6mm or less, and Group 2 above 6mm. Control group was two adults wish normal speech patterns. A phonetician performed narrow phonetic transcriptions of tape-recorded words and sentences produced by each of the patients and the acoustic characteristics of the plosives, fricatives, and flaps were analyzed with a phonetic computer program (Computerized Speech Lab(CSL) Model 4300B(USA)). The results are as follows: 1. Generally, Patients showed longer closure duration of plosives, shorter VOT(voice onset time) and higher ratio of closure duration against VOT. 2. Patients showed more frequent diffuse distribution than the control group in frication noise energy of fricatives. 3. In fricatives, frequency of compact from were higher in group 1 than in group 2. 4. Generally, a short duration of closure for /ㄹ/ was not realized in the patient's flaps. Instead, it was realized as fricatives, sonorant with a vowel-like formant structure, or trill type consonant. 5. Abnormality of the patient's articulation was reduced, but adaptation of their articulation after surgery was not perfect and the degree of adaptation was different according to the degree of surgical setback.

• Journal of the Korean Society of Radiology
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• v.13 no.7
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• pp.1025-1033
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• 2019

Although magnetic resonance imaging without linear hardening of CT is recognized as a method of obtaining high contrast of tissue and excellent resolution image in brain disease and head and neck examination, magnetic susceptibility artifact is generated in case of metal implants in the oral cavity, which is an obstacle to image diagnosis. Therefore, an effort was made in this thesis to find a method to reduce artifacts caused by dental implants and prosthesis in MRI. Implant-induced artifacts in magnetic resonance imaging showed that the signal size increased with shorter TE in GE technique and was inconsistent with water temperature change. In SE technique as well, the signal size of water was generally higher than that of air, but the signal to noise ratio (SNR) was not different by air and temperature. In EPI technique, images with fewer artifacts were obtained quantitatively and qualitatively when there was more water than air, and the signal to noise ratio was measured the highest, especially at water temperatures of 20° and 30°. In conclusion, when examining using the EPI technique rather than the SE or the GE technique, obtaining brain diffusion using a 20° and 30° water bag reduces the magnetic susceptibility artifacts caused by implants and prosthesis, suggesting that it may provide images with high diagnostic value.

• Journal of Sensor Science and Technology
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• v.29 no.4
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• pp.249-254
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• 2020

It is difficult to control children who exhibit negative behavior in dental clinics. Various methods are used for preventing pediatric dental patients from being afraid and for eliminating the factors that cause psychological anxiety. However, when it is difficult to apply this routine behavioral control technique, sedation therapy is used to provide quality treatment. When the sleep anesthesia treatment is performed at the dentist's clinic, it is challenging to identify emergencies using the current breath detection method. When a dentist treats a patient that is under the influence of an anesthetic, the patient is unconscious and cannot immediately respond, even if the airway is blocked, which can cause unstable breathing or even death in severe cases. During emergencies, respiratory instability is not easily detected with first aid using conventional methods owing to time lag or noise from medical devices. Therefore, abnormal breathing needs to be evaluated in real-time using an intuitive method. In this paper, we propose a method for identifying abnormal breathing in real-time using an intuitive method. Respiration signals were measured using a 3M Littman electronic stethoscope when the patient's posture was supine. The characteristics of the signals were analyzed by applying the signal processing theory to distinguish abnormal breathing from normal breathing. By applying a short-time Fourier transform to the respiratory signals, the frequency range for each patient was found to be different, and the frequency of abnormal breathing was distributed across a broader range than that of normal breathing. From the wavelet transform, time-frequency information could be identified simultaneously, and the change in the amplitude with the time could also be determined. When the difference between the amplitude of normal breathing and abnormal breathing in the time domain was very large, abnormal breathing could be identified.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.4
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• pp.16-21
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• 2013

This paper presents a DC link voltage control method to reduce the ripple current and the switching loss in the sinusoidal current drive system for the wide-speed range PMSM. The DC link voltage of the three phase inverter in the sinusoidal current drive system is designed by the back-EMF voltage at maximum speed of the PMSM. In general, the drive systems have used the constant DC link voltage without reference to the motor speed. The current ripple causes hysteresis loss and makes noise. In addition, the switching loss on the inverter increases in proportion to the rise in the DC link voltage. In this paper, we propose the variable DC link voltage control method to reduce the current ripple in the PMSM drive system. We show reduction effect of the current repple and the switching loss through simulation results.

• Journal of Magnetics
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• v.22 no.2
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• pp.220-226
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• 2017

SNR (signal to ratio) is a criterion for providing objective information for evaluating the performance of a magnetic resonance imaging device, and is an important measurement standard for evaluating the quality of MR (Magnetic Resonance) image. The purpose of our study is to evaluate the correct SNR measurement for multi-channel coil and parallel imaging. As a result of research, we found that both T1 and T2 weighted images show the narrowest confidence interval of the method recommended by NEMA (The National Electrical manufacturers Association) 1 having a single measurement method, whereas the ACR (American College of Radiology) measurement method using a multi-channel coil and a parallel imaging technique shows the widest confidence interval. There is a significance in that we quantitatively verified the inaccurate problems of a signal to noise ratio using a ACR measurement method when using a multi-channel coil and a parallel imaging technique of which method does not satisfy the preconditions that researchers could overlook.