• Journal of Korean society of Dental Hygiene
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• v.20 no.3
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• pp.281-290
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• 2020

Objectives: Stress is the cause of several illnesses, in older people, stress may also cause various social problems. The oral health of older adults is closely related to the quality of life, and chewing ability is particularly important for their general health. The purpose of this study was to investigate the relationship between stress, the number of teeth remaining, and the chewing ability, which reflects the oral health status among older adults. Methods: This study evaluated the stress level and chewing ability of adults older than 65 years using the 6th (2014-2015) Korea National Health and Nutrition Examination data. The total number of remaining teeth was determined based on the data of the teeth conditions. Results: There was an association between stress and chewing ability among older adults. The odds ratio of chewing function increased by 2.67 times (crude OR=2.67; 95% CI=1.88-3.79) with increased stress. After adjusting, the odds ratio increased to 2.74 times (adjusted OR=2.74; 95% CI=1.88-3.98). Conclusions: Reducing stress may facilitate effective oral health management and improve the overall quality of life in older adults. The findings of this study may help in the discovery of various approaches s to reducing stress in older adults and provide relevant information for oral health education.

• Journal of the korean academy of Pediatric Dentistry
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• v.29 no.4
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• pp.574-578
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• 2002

Mesiodens is developmental tooth anomaly which is commonly found in clinical pediatric dentistry. however, it may cause many partial problem in tooth alignment when congenitally missing teeth was accompanied by mesiodens. The terms, concomitant hypodontia and hyperdontia' and oligo-pleiodontia' have been used to describe the condition in witch developmental absence of teeth and supernumerary teeth are present in the same individual. Only a few case reports of this rare condition which is opposite developmental phenomena exist in the literature. The purpose of this study is survey of congenitally missing teeth in mesiodens case and to compare previous literature of congenitally missing teeth in normal. The subjects were 310 children(247 male and 63 female) at the age from 5 to 12 years visiting the Department of Pediatric Dentistry, Pusan National University Hospital with mesiodens for last 3 years. With their pantomograms we studied congenitally missing teeth except permanent 3rd molar. 1. The preference of congenitally missing teeth in mesiodens cases was revealed to be 17.1%(53 out of 310 in total), and there was a higher prevalence in females(22.2%) than in males(15.8%). 2. The most frequently missing teeth were maxillary lateral incisors(22.7%) and mandibular second premolars(22.7%), followed by maxillary second premolar(17.3%), and mandibular lateral incisors(16.0%). There was no significant differences between maxilla(49.3%) and mandible(50.7%). 3. In number of congenitally missing teeth per person, 69.9% had one missing tooth, 22.7% had two missing teeth and 9.4% had three missing teeth.

• Journal of Korean society of Dental Hygiene
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• v.22 no.5
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• pp.417-424
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• 2022

Objectives: This study aimed to find a way to solve oral health inequality in old age by understanding the effect of the socioeconomic level of the elderly on oral health. Methods: We used data from the 7th Korea National Health and Nutrition Examination Survey. A chi-square test was performed to investigate differences in oral health according to socioeconomic status and demographic and oral health-related factors. Socioeconomic status and oral health inequality were analyzed using multiple logistic regression. Results: The average number of teeth in the elderly was 17.20, which is insufficient for the minimum number of teeth required for mastication. In the analysis of the correlation between socioeconomic status and oral health inequality, education level, income level, and home ownership were factors influencing the oral health of the elderly; education level was found to have the strongest effect. Conclusions: Oral health inequality according to socioeconomic status was confirmed, and it is necessary to measure the level of oral health inequality with active efforts at the government level to resolve the gap in oral health by social class.

• Journal of Korean society of Dental Hygiene
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• v.9 no.4
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• pp.620-632
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• 2009

Objectives : The present study purposed to survey the oral health-related quality of life among elderly in metropolis Methods : We had individual interviews and oral survey using a questionnaire with 336 elderly who were using seniors' centers in Metropolitan City during the period from the $9^{th}$ to $31^{st}$ of July, 2007. Results : Factors of GOHAI showed the significant relation with types of health insurance, a large number of medication, perceived oral health status, perception of dental care needs those with pains in the temporomandibular joint, the number of natural teeth and the explanatory power or the final model was 25.5%. Factors of OHIP-14 showed the significant relation with types of health insurance, a large number of medication, perception of dental care needs those with pains in the temporomandibular joint, gingival bleeding, the number of natural teeth and the explanatory power or the final model was 26.6%. Conclusions : Oral health-related quality of life among elderly as factors by general characteristics of study subjects, by perceived heath status and oral health status, perceived oral symptoms and oral health status that were relevant. Accordingly, for the healthy maintenance of elders' natural teeth, it is considered necessary to develop and execute continuous oral health management systems and oral health education programs that promote preventive activities and enhance the perception of oral health.

• Restorative Dentistry and Endodontics
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• v.46 no.4
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• pp.49.1-49.8
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• 2021

Objectives: To evaluate the fracture incidence of Reciproc R25 instruments (VDW) used during non-surgical root canal retreatments performed by students in a postgraduate endodontic program. Materials and Methods: From the analysis of clinical record cards and periapical radiographs of root canal retreatments performed by postgraduate students using the Reciproc R25, a total of 1,016 teeth (2,544 root canals) were selected. The instruments were discarded after a single use. The general incidence of instrument fractures and its frequency was analyzed considering the group of teeth and the root thirds where the fractures occurred. Statistical analysis was performed using the χ² test (p < 0.01). Results: Seven instruments were separated during the procedures. The percentage of fracture in relation to the number of instrumented canals was 0.27% and 0.68% in relation to the number of instrumented teeth. Four fractures occurred in maxillary molars, 1 in a mandibular molar, 1 in a mandibular premolar and 1 in a maxillary incisor. A greater number of fractures was observed in molars when compared with the number of fractures observed in the other dental groups (p < 0.01). Considering all of the instrument fractures, 71.43% were located in the apical third and 28.57% in the middle third (p < 0.01). One instrument fragment was removed, one bypassed, while in 5 cases, the instrument fragment remained inside the root canal. Conclusions: The use of Reciproc R25 instruments in root canal retreatments carried out by postgraduate students was associated with a low incidence of fractures.

• Journal of dental hygiene science
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• v.2 no.2
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• pp.89-94
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• 2002

The present study attempts to find the ways to efficiently manage dental caries, one of the major causes of tooth loss, and to cope with oral diseases that deteriorate oral health. For this purpose, this study seeks to obtain fundamental data needed in planning the oral health projects. The study was conducted to the first-grade elementary school students in Hwa-Seong city, Gyeonggi-do, from April 1 - 30, 2002. The result was as follows: 1) Among a total of 2,710 subjects, 598 (274 boys and 324 girls) have more than 1 permanent tooth with a caries legion whether it was treated or not. 2) The number of permanent teeth examined is 6,029, in which girls' teeth are more (3,165) than boys' (2,864). 3) Out of a total of 6,029 teeth examined, 1,106 permanent teeth (508 boys' and 598 girls') have caries legions. 4) Out of 1,106 permanent teeth with caries legions, 170 (15.4%) were treated - 67 teeth for boys (13.2%) and 103 teeth for girls (17.2%). 5) 22.1% of the children have experienced dental caries in their permanent teeth. Among them, 20.1% are boys and 24.1% are girls. 6) The rate of the permanent teeth that once had, or now have caries legions are 21.2%, among which the rate for boy's teeth is 20.1% and that for girl's teeth is 22.1%. 7) The number of the permanent teeth that had caries legions is 0.5 for all the subjects. A boy has 0.4 and a girl has 0.5 teeth with caries legions regardless of whether it was treated or not. 8) The rate of the permanent teeth with caries legions is 86.7% for overall subjects - 88.3% for boys and 85.3% for girls. 9) The rate of treated permanent teeth is 13.3% for all the subjects - 11.7% for boys and 14.7% for girls. Based on the above result, the study draws a conclusion that in order to prevent dental caries in young students and to perform an early treatment for the dental caries that already occurred an oral health office should be installed at all the elementary schools so that elementary school students don't experience a loss of time and effort for learning and suffer nutritional imbalance or disorder. Besides, the oral health education concerning the importance of dental care should be conducted to the citizens, especially to the young people, in the community as an essential project of oral health centers in the community health offices, the public medical institutions.

• The Journal of the Korean dental association
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• v.13 no.4
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• pp.335-337
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• 1975

The auther observed the oral status of the 14 twins clinically, the obtainde results were as follow : 1. In each twins, the color of the teeth, the form of the uper central incisors, the periodontal conditions and the oral hygiene status were resemble each other. 2. In one twin, the dentition and the size of the palatine tonsil were different each other. 3. In two twins, the occlusion and the number of the dental caries were different each other. 4. In four twins, the eruptions of teeth were different each other.

• Tribology and Lubricants
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• v.16 no.5
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• pp.324-331
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• 2000

Wear characteristics of Plastic and Nylon pinions against steel gear were studied to gain a better understanding of their tribological behaviors. Wear tests were conducted with power circulating gear test rig under dry contact conditions. Specific wear rates were measured as a function of applied load and the number of revolution. The worn teeth surfaces were examined with a profile projector and a camera. Nylon pinion showed lower specific wear rates than acetal pinion, but suffered teeth breakage under high load per unit tooth width. The dominant wear mechanisms found were adhesion and abrasion.

• The korean journal of orthodontics
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• v.23 no.3 s.42
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• pp.375-389
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• 1993

The delivery of optimal orthodontic treatment is greatly influenced by a clinician's ability to predict and control tooth movement achieved by applying known force systems to the dentition. It is important to determine the location of the center of resistance of a tooth or group of teeth to better understand the nature of their displacement characteristics under the various force levels. The purpose of this study was to define the location of the centers of resistance of various units of the upper anterior segment for lingually directed 100gm and 200gm force in a dry human skull. The units investigated were composed of four incisors and six anterior teeth. In addition, the effect of change in force magnitude on the location of the center of resistance of these units was investigated. The laser reflection technique was used to measure the initial displacements of the consolidated teeth under loading. The results were as follows: 1. The instantaneous center of resistance for the four anterior teeth was located vertically between level 4 and level 5-that is, at $37.4\%$ apical to the cementoenamel junction level. 2. The instantaneous center of resistance for the six anterior teeth was located vertically just beneath level 5-that is, at $50.3\%$ apical to the cementoenamel junction level. 3. Increasing force levels had little effect on the location of the center of resistance of a given unit. 4. The location of the instantaneous center of resistance shifted apically as the number of dental units consolidated increased.

• The Journal of Korean Academy of Prosthodontics
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• v.32 no.2
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• pp.296-326
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• 1994

The purpose of this study was to evaluate the mechanical effects when one implant fixture was connected to the natural teeth with reduced alveolar bone height. This study also examined the effects of increasing the number of abutment teeth and the effects of the intramobile connector and the titanium connector as they were inserted between the implant superstructure and the fixture. The distribution and concentration load was applied to the fixed partial denture(FPD) supported by implant and the natural teeth with reduced alveolar bone height. The stress and displacement of each element was observed and compared by the two-dimensional finite element method. The following results were obtained : 1. The greater the loss of alveolar bone in natural teeth area, the greater the displacement of FPD and the stress concentration in alveolar bone around implant, especially at the stress concentration in the mesial alveolar bone crest around implant fixture. 2. The displacement of FPD was increased more and that of implants fixture was decreased more when intramobile connector was used than titanium connector was used. Also the stress concentration in alveolar bone around implant fixture was greater when intramobile connector than titanium connector. One implication of this finding was that the difference in stiffness of implant and the natural teeth with reduced alveolar bone height could be partially compensated in case of the POM intramobile connector. 3. The amount and direction of displacement and the stress distribution of the 4-unit FPD was better than those of the 3-unit FPD. It implied that the difference of stiffness of implant and natural teeth with reduced alveolar bone height could be partially compensated in case of the 4 unit FPD.