• Restorative Dentistry and Endodontics
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• v.28 no.1
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• pp.34-40
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• 2003

Chewing simulator, which can partly mimic the motion of chewing motion of human, has been successfully developed. The purpose of its development was to make a new machine which can anticipate the clinical results of restoration in the human teeth more accurately in vitro condition It is composed of 4 major parts, chewing part, motor part, water bath, controlling part. The controlling part control the chewing force, frequency, the temperature and running time of water. Additionally, the actual chewing force and remaining time is shown in the monitor of controlling part. At present, the chewing cycle is composed depending on the pre-published data of foreign people. Long term clinical data should be additionally collected for the simulator to mimic the clinical results more accurately.

• The Journal of Korean Academy of Prosthodontics
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• v.24 no.1
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• pp.117-124
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• 1986

Numerous studies have been reported on the movement of the jaw during chewing. However, there is still much controversy. The purposes of this study were to observe the jaw movement during mastication and to provide the information in prosthodontic treatment and diagnosis of temporomandibular disorder. The author analyzed the time and characteristics of the masticatory movement during chewing using mandibular kinesiograph in 24 subjects, 17 males 7 females, age of 22-27 without orofacial problems. The obtained results were as follows: The duration of single chewing cycle was $515{\pm}87msec.$. Comparing the three phases of the chewing cycle (opening, closing, centric pause), the closing phase had the longest duration, and the centric pause had the shortest duration. The maximal laterotrusive movement of the mandible druing chewing was $3.5{\pm}1mm$. The maximal mediotrusive movement of the mandible during chewing was $1.0{\pm}0.7mm$. The maximal vertical velocity of the mandible during chewing was $120{\pm}28mm/sec.$ in opening phase, and $109{\pm}21mm/sec.$ in closing phase.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.9
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• pp.769-775
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• 2016

Currently, dental implants are widely used as artificial teeth due to their good chewing performance and long life cycle. Generally, a dental implant consists of an abutment as the upper part and a fixture as the lower part. When chewing forces are repeatedly applied to a dental implant, a gap is often generated at the interfacial surface between the abutment and the fixture, and it results in some deterioration such as loosening of the fastening screw, dental retraction and fixture fracture. To enhance the sealing performance for coping with such problems, this study proposes a new sealing-type abutment having a number of grooves along the conical surface circumference, and it carries out finite element analysis in consideration of the external chewing force and pretension between the abutment and the fixture. The result shows that the proposed sealing-type abutment shows an enhanced sealing performance in terms of the contact pressure in comparison with a conventional abutment.

• The korean journal of orthodontics
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• v.44 no.3
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• pp.143-153
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• 2014

An 8-years old boy with facial asymmetry and unilateral posterior crossbite on the left side received orthopedic and orthodontic treatment. During the first phase of treatment, the narrow maxillary arch was expanded using an acrylic plate. Then, the acrylic plate was used as a bite block with occlusal indentations from the construction bite that was obtained with the incisors in a coincident dental midline. After the position of the mandible was stabilized, the second phase of orthodontic treatment was initiated using fixed appliances for detailing of the occlusion. Skeletal symmetry, ideal occlusion, and coincident dental midlines were thus achieved. Functionally, occlusal force balance and masticatory muscle activity were improved, and the chewing patterns were normalized.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.6
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• pp.24-30
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• 2018

Dental implants are currently widely used as artificial teeth due to their good chewing performance and long life cycle. A dental implant consists of an abutment as the upper part and a fixture as the lower part. When chewing forces are repeatedly applied to a dental implant, gap at the interface surface between the abutment and the fixture is often occurred, and results in some deteriorations such as loosening of fastening screw, dental retraction and fixture fracture. To cope with such problems, a sealing-type abutment having a number of grooves along the conical-surface circumference was previously developed, and shows better sealing performance than the conventional one. This study carries out optimization of the groove shape by genetic algorithm(GA) as well as structural analysis in consideration of external chewing force and pretension between the abutment and the fixture. The overall optimization system consists of two subsystems; the one is the genetic algorithm with MATLAB, and the other is the structural analysis with ANSYS. Two subsystems transmit and receive the relevant data with each other throughout the optimization processes. The optimization result is then compared with that of the conventional one with respect to the contact pressure and the maximum stress. The result shows that the optimized model gives better sealing performance than the conventional sealing abutment.

• The Journal of Advanced Prosthodontics
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• v.12 no.5
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• pp.283-290
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• 2020

PURPOSE. The present study aimed to evaluate the clinical applicability of monolithic zirconia (MZ) crowns of different thickness via determination of fracture resistance and marginal fit. MATERIALS AND METHODS. MZ crowns with 0.5, 0.8, 1.0, and 1.5 mm thickness and porcelain fused to metal (PFM) crowns were prepared, ten crowns in each group. Marginal gaps of the crowns were measured. All crowns were aged with thermal cycling (5 - 55℃/10000 cycle) and chewing simulator (50 N/1 Hz/lateral movement: 2 mm, mouth opening: 2 mm/240000 cycles). After aging, fracture resistance of crowns was determined. Statistical analysis was performed with one-way ANOVA and Tukey's HDS post hoc test. RESULTS. Fracture loads were higher in the PFM and 1 mm MZ crowns compared to 0.5 mm and 0.8 mm crowns. 1.5 mm MZ crowns were not broken even with the highest force applied (10 kN). All marginal gap values were below 86 ㎛ even in the PFM crowns, and PFM crowns had a higher marginal gap than the MZ crowns. CONCLUSION. The monolithic zirconia exhibited high fracture resistance and good marginal fit even with the 0.5 mm thickness, which might be used with reduced occlusal thickness and be beneficial in challengingly narrow interocclusal space.

• Journal of Korean society of Dental Hygiene
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• v.21 no.5
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• pp.595-600
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• 2021

Objectives: For postmenopausal women who participated in the 2019 National Health and Nutrition Examination Survey, we aimed to provide basic data for oral health management interventions and oral policies for each life cycle of postmenopausal women by identifying the relationship between physical activity and depression on oral health behavior and awareness symptoms. Methods: The participants of this study were 1,628 menopausal women, and their general characteristics, physical activity, depression, and oral health behavior and awareness symptoms were investigated. This study used the complex sample frequency analysis, complex sample 𝞆² test, and logistic regression analysis method, which is a sample design of the National Health and Nutrition Examination Survey. Results: The factors influencing physical activity were the use of oral hygiene device and chewing difficulty. and the influencing factors of depression experience were pain and chewing difficulty. Conclusions: As a result, physical activity and depression experience should be utilized by developing and oral health program for the promotion of oral health in postmenopausal women.

• The Korean Journal of Pain
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• v.27 no.3
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• pp.260-265
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• 2014

Background: To evaluate the results of conventional radiofrequency thermorhizotomy (CRT) for trigeminal neuralgia (TN) in patients with failed medical management. Methods: Patients with Trigeminal neuralgia who were referred to us for 'limited intervention' during the time frame July-2011 to Jan-2013 were enrolled for this study. CRT was administered by the Sweet technique. Pain relief was evaluated by the principle investigator. Results: Eighteen patients were enrolled and completed a mean follow-up of 18.0 months. Pain relief was observed in 14 of 18 (77.8%) patients on the post-operative day, 14 of 18 (77.8%) at 1-month follow-up, 14 of 17 (82.4%) at 3-months follow-up, 12 of 15 (80%) at 6-months follow-up, 7 of 11 (63.6%) at 1-year follow-up and 2 of 6 (33.3%) 1.5 years of follow-up. Four patients required a repeat cycle of CRT; two at six months of follow-up and two at one year of follow-up. One patient was transferred for surgical intervention at six months of follow-up. Side-effects included facial hypoesthesia (n = 6); nausea/vomiting (n = 2), diminished corneal reflex (n = 13) and difficulty in chewing (n = 11). Severity of adverse effects gradually diminished and none of the patients who are beyond 6 months of follow-up have any functional limitation. Conclusions: CRT is an effective method of pain relief for patients with Trigeminal neuralgia. Successful outcome (excellent or good) can be expected in 66.7% of patients after first cycle of CRF. The incidence and severity of adverse effects is less and the procedure is better tolerated by the patients.

• Journal of Korean society of Dental Hygiene
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• v.23 no.4
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• pp.245-250
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• 2023

Objectives: This study was conducted to analyze the factors related to unmet dental care needs in Korean adults who needed dental treatment. Methods: This study analyzed data from the 7th Korea National Health and Nutrition Examination Survey (2016-2018). Among the adults who participated in the National Health and Nutrition Examination Survey, 2,723 dental treatment who performed oral examinations were the final subjects. General characteristics and oral health characteristics were analyzed with complex sample chi-square test using the IBM SPSS program. Factors related to unmet dental care were analyzed by multiple logistic regression analysis. Results: As for unmet dental care needs related factors, bad oral health was 3.383 times higher, and usually was 1.736 times higher. In the use of dental clinic unmet dental care needs was 0.121 times lower. Unmet dental care needs was high, 1.366 times for those with the experience of tooth pain and 2.736 times for those with chewing difficulty. Conclusions: Based on the above results, it can be seen that oral health status or oral discomfort is related to unmet dental care needs. It is necessary to set goals to improve unmet dental care, recognize that one's oral health condition is very important, and continuously educate about oral health for each life cycle.

• Journal of Korean society of Dental Hygiene
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• v.18 no.3
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• pp.347-358
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• 2018

Objectives: The purpose of this study is to identify the association between oral health status and pulmonary ventilatory defects. Methods: The 6th (2013-2015) National Health and Nutrition Examination Survey data was used. The study subjects were those aged 40-79 who had pulmonary function examination. Complex samples general linear model analysis, Complex samples cross-tabulation analysis, and Complex samples logistic regression analysis were conducted. Results: In terms of restrictive ventilatory defects, the study subjects (8.3%) who recognized that their oral health status was bad outnumbered those who recognized that their oral health status was good (6.1%) (p<0.05). Many of the study subjects who experienced difficulty in biting, chewing and/or speech, and who had an unhealthy periodontal had restrictive ventilatory defects and obstructive ventilatory defects (p<0.05). The association between oral health status and pulmonary ventilatory defects was analyzed. The findings showed that those who had unhealthy periodontal had a 1.33 times higher probability of pulmonary ventilatory defects than those who had a healthy periodontal (p<0.05). After taking into account general characteristics (age, sex, incomes, education, and smoking) of the subjects, the association between oral health status and pulmonary ventilatory defects was analyzed. The result found that only in cases where one experienced dental caries was an association with pulmonary ventilatory defects found. In other words, those who had dental caries showed a 0.73 times higher probability of pulmonary ventilatory defects than those who had no dental caries (p<0.05). Conclusions: Based on the findings of this research, oral health status was found to be associated with pulmonary ventilatory defects. To improve oral health, it is necessary to provide life-cycle stages based oral health education. Therefore, it is required to develop an oral health education program and develop a national oral health policy.