• 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.

• Nutrition Research and Practice
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• v.16 no.3
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• pp.354-365
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• 2022

BACKGROUND/OBJECTIVES: Understanding the mechanism of chewing and swallowing food is important when creating a proper diet for older adults. This study investigated whether texture-modified model foods can reduce the difference in chewing and swallowing parameters between healthy community-living young and older adults. SUBJECTS/METHODS: In total, 35 older and 20 young adults (mean age: 75 and 25 years, respectively), matched for sex and number of teeth, were recruited and their unstimulated salivation and tongue pressure were measured. Simultaneous assessment of chewing and swallowing characteristics was conducted using surface electromyography and a videofluoroscopic swallowing study while the participants ingested 8 g of model food with one to four levels of hardness. RESULTS: The average tongue pressure and salivation among older adults were 61% and 49.7%, respectively, of the corresponding values observed in young adults. The older adult group used significantly (P < 0.05) increased muscle force with more chewing cycles (P < 0.05) than the young adult group, which was maintained even when consuming foods with the lowest hardness, although without chewing. However, the age effect on oral processing time existed only for the hardest foods. Swallowing difficulties among older adults were demonstrated by the significant increase in vallecula aggregation time. The total food intake duration was significantly (P < 0.05) longer in older adults than in young adults, regardless of food hardness. CONCLUSIONS: There were measurable differences in the process of chewing and swallowing food between young and older adults, which can be improved with food hardness control. Adjusting food hardness may help food intake in healthy older adults.

• The Journal of Korean Academy of Prosthodontics
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• v.62 no.4
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• pp.339-348
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• 2024

An implant-supported hybrid prosthesis is a fixed restoration composed of a metal framework and acrylic resin, offering advantages such as aesthetics, function, phonetics, and lip support, while providing retention and support through the splinting of implants with the metal framework. However, poor oral hygiene can lead to peri-implantitis, and long-term use may result in wear or fracture of the artificial teeth, causing reduced masticatory function and loss of vertical dimension. Traditionally, a new metal framework is cast for remanufacturing, but if the existing framework is intact, it can be reused for a more rapid and simplified protocol. This case involves a 58-year-old male patient with peri-implantitis, where some implants were removed and treated, and the superstructure was remanufactured using the existing metal framework. By preserving the existing metal framework during the remanufacturing of the implant-supported hybrid prosthesis, the treatment time and number of visits were reduced, minimizing patient discomfort.

• Korean Journal of Plant Taxonomy
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• v.38 no.2
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• pp.93-109
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• 2008

The morphological variation was analysed to examine previous hypotheses on the taxonomy of B. amurensis complex which includes B. amurensis Rupr. var. amurensis, B. amurensis var. quelpaertensis (Nakai) Nakai and B. amurensis var. latifolia Nakai. The results from the univariational and principal components analyses employing 22 putatively diagnostic characters indicate that B. amurensis var. quelpaertensis is distinct from var. amurensis in the length and width of leaves, angle of leaf apex, distance between spinose teeth, length of internode, number of flowers per inflorescence, whereas B. amurensis var. latifolia is different from other varieties in the angle of leaf apex and leaf length/width ratio. In principal component analysis, the characters of the leaf including leaf width and length were the main characteristics to distinguish those three taxa. The evidence both from the principal components analyses and current geographical distribution pattern suggest that retaining the varietal status for the two taxa, B. amurensis var. latifolia and B. amurensis var. quelpaertensis is reasonable.

• Journal of Convergence for Information Technology
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• v.11 no.12
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• pp.265-274
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• 2021

The purpose of this study is to provide basic data for confirming the convergence relationship between flexibility exercise on quality of life, oral condition, and oral health-related behavior. Data from the 2012 KNHNES were used, and complex sample linear regression analysis and logistic regression analysis were performed to confirm the effects of flexibility exercise on quality of life and oral health. As a result, those who controlled for demographic characteristics and did not exercise flexibility had .027 times worse exercise ability among the subcategories of quality of life, and .152 times higher number of carious permanent teeth. Among the symptoms of temporomandibular joint disorder, pain symptoms were 1.633 times higher in those who exercised flexibility (p<.05). Therefore, it is considered that flexibility exercise has value in that it has suggested a relationship not only with general health but also with oral health.

• Journal of Korean society of Dental Hygiene
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• v.19 no.4
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• pp.565-575
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• 2019

Objectives: In this study, both subjective and objective levels of oral health were used to identify the relationship between oral health inequalities. Methods: Korean National Health and Nutritional Examination Survey data from 2013 to 2015 were combined to create an analysis plan. Oral health questions categorized as subjective oral health conditions and oral health-related diseases used dental tissue disease status as data measured by the Community Periodical Index(CPI) and decayed, missing, filled teeth(DMFT) experience. Other data on oral health behaviors such as toothache experience, the frequency of toothbrush use, chewing problems, oral examination status, and unmet dental care needs were classified and analyzed according to the socioeconomic level. Data were analyzed using frequency and cross analyses, and the statistical significance level was set at 0.05. Results: It was found that higher the economic and educational level, better was the subjective oral health, lower the CPI, lower the experience of toothache, higher the frequency of toothbrush use, lower the number of people having chewing problems, and higher the frequency of oral checkups. Conclusions: Oral health inequality exists among social classes. It is suggested that continuous research and efforts be carried out to promote oral health while considering socioeconomic and educational levels. Further, active government efforts will be needed to address polarization by social class.

• The Journal of Korean Academy of Prosthodontics
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• v.57 no.4
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• pp.416-424
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• 2019

Peri-implantitis appears in almost 20% of patients who received implant treatment, and increase in its number is inevitable as time goes by. Although it can be treated by both non-surgical and surgical procedures, in cases which include severe bone loss, explantation and rehabilitation may be necessary. Careful treatment planning and considerations to prevent recurrent peri-implantitis should be taken into account. In the following case presented, a patient with chronic periodontitis and peri-implantitis was successfully rehabilitated after removal of several implants. Extraction and explantation of multiple teeth and implants were followed by full mouth reconstruction with fixed implant prostheses on the mandible and implant retained overdenture on the maxilla. Surgical and prosthetic measures to prevent recurrent peri-implantitis were taken into consideration.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.7
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• pp.4353-4360
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• 2014

This study examined the relationship between the current chewing difficulty and the dental prosthesis needs of the elderly Koreans to improve their oral health status. A total of 1,177 subjects over 65 years who participated in the the Five Korea National Health and Nutrition Examination Survey were examined. An oral examination was conducted to determine the number of missing teeth and dental prosthesis required. A questionnaire was given to measure the sociodemographic characteristics, concerns about oral health, chewing ability and pronunciation ability. Statistical analysis was done using the SPSS 19.0 program. The percentage of the current chewing difficulty in Korean elderly was 42.9%. After adjusting for confounder variables, the odds ratio of the fixed prosthodontics needs were 1.22 (95% CI; 0.74 to 2.02), the odds ratio of partial denture needs were 2.47 (95% CI; 1.71 to 3.56) and the odds ratio of the full denture needs were 2.06 (95% CI; 0.73 to 5.81). The dental prosthesis needs were associated with the current chewing difficulty. Therefore, dental prosthesis support policy and public oral health promotion for the elderly is necessary.

• Journal of the Ergonomics Society of Korea
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• v.31 no.2
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• pp.319-325
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• 2012

Objective: The aim of this study was to develop the assistive device for accelerator and brake pedals using bio-signals from the prefrontal lobe in the driving simulator and evaluate its performance. Background: There is lack of assistive devices for the driving in peoples with disabilities in Korea. However, if bio-signals and/or brain waves are used at driving a car, the people with serious physical limitations can improve their community mobility. Method: 15 subjects with driver's license participated in this study for experiment of driving performance evaluation in the simulator. Each subject drove the simulator the same course 10 times in three separated groups which use different interface controllers to accelerate and brake: (1) conventional pedal group, (2) joystick group and (3) bio-signal group(horizontal quick glance of the eyes and clench teeth). All experiments were recorded and the driving performances were evaluated by three inspectors. Results: Average score of bio-signal group for the driving in the simulator was increased 3% compared with the pedal group and was increased 9% compared with the joystick group(p<0.01). The subjects using bio-signals was decreased 44% in number of deduction compared with others because the device had the built-in modified cruise control. Conclusion: The assistive device for accelerator and brake pedals using bio-signals showed significantly better performance than using general pedal and a joystick interface(p<0.01). Application: This study can be used to design adaptive vehicle for driving in people with disabilities.

• The Journal of the Korea Contents Association
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• v.20 no.2
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• pp.352-359
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• 2020

This study utilizes raw data from the first-ever Korea National Health and Nutrition Examination Survey (KNHANES) conducted in 2017 and its purpose is to identify factors that influences Daily toothbrushing frequency and use of oral health care products for adolescents aged 13 to 18 years in conjunction with their mothers. Factors affecting Daily toothbrushing frequency of adolescents are: Whether the mother smokes or not, and Daily toothbrushing frequency for the mother. The more the mother younger and smoked and brushed her teeth, the higher the number of sessions increased for the adolescent child. The higher the mothers' level of education and use of oral care products were the greater the adolescent child's use of oral care products became. As a result, the study determined that the oral health of adolescents and of their mothers are closely related. A program to educate adolescents and mothers to promote the oral health of adolescents should be developed, and continuously and systematically implemented at home and school.