• Journal of dental hygiene science
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• v.4 no.3
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• pp.91-95
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• 2004

This study aims to analyze realities of oral health and related factors, and establish Structural Equation Modeling. The subjects of study were 9,340 elderly over age 65 who took the health examination(the first) for the local insured which National Health Insurance Corporation carried out in the survey area mentioned below from January 2002 to December 2002. The areas surveyed were 4 big cities including Seongbuk-ku, Seoul, 5 medium cities including Wonjusi, Gangwon-do, and 5 Counties including Yeong deok County, Kyeongbuk. Considering location and the scale of population, firstly, big unit areas(metropolitan city, province) were selected according to convenience, secondly, low unit areas(city, county, district) were selected randomly. The subjects were the elderly who took all tests including an oral examination and filled in the questionnaire. Major results from analysis are as follows: 1. Review of Composition Conception Validity As a result of analyzing composition conception validity of SEM including posture test, urine test, blood test, habits of eating, drinking and smoking, oral symptoms, and oral health status, using fit index such as GFI, CFI, TLI, and RMSEA, all were within fit range and composition conception validity was recognized. 2. As a result of analyzing SEM to find the relationship between each factor and oral health status, it was confirmed that all factors except urine test affected oral health status and the synthetic SEM to explain it could be established. In result, we could verify that the elderly of rural areas who had lesser experience of visiting a clinic and oral prophylaxis had a higher rate of caries, missing teeth, and denture need, and drinking and smoking negatively affected the rate of caries, periodontal, and missing teeth. Also, periodontal diseases were observed from 43.2% of the total elderly and much from the lower age. Most of oral disease can be prevented by right oral health behavior. Therefore through oral health professionals from each district public health center of the nation, oral health education for the elderly about right eating habits and oral health care should be carried out systematically and policy change to increase access to dental service is required lest that visiting a dental clinic should be impossible or oral health behaviors such as oral prophylaxis and denture wearing should be neglected by economic, geographical barriers. Also, to establish SEM to explain the relationship between oral health status and systemic health, more accurate test methods and effective index development should be preceded. Because items developed by National Health Insurance Corporation applied to this study without alteration, structuring a model had the uppermost limit. Continual study seems to be needed.

• Applied Chemistry for Engineering
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• v.16 no.5
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• pp.672-676
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• 2005

To improve the application of polymeric dental restorative composite (PDRC) for the posterior and anterior restoration, silica bridged with siloxane unit was firstly prepared by heat-treating a silica filler at various temperatures. Degree of conversion (DC), depth of cure, and dynamic volumetric polymerization shrinkage values of PDRC filled with silica bridged with siloxane unit were investigated to study the effect of heat-treated silica on the polymerization behavior of PDRC. From the experimental result, it was found that depth of cure was decreased with an increase of heat treatment temperature. on the other hand, both DC and polymerization shrinkage values were uniformly enhanced with increasing the heat treatment temperature. This phenomenon can be explained from the study that showed decrease of average particle size of silica resulted in the increase of relative amount of resin matrix in PDRC.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.11a
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• pp.42.2-42.2
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• 2009

인체의 치아 및 뼈는 무기질 성분과 단백질로 구성되어 있다. 생체세라믹스의 일종인 수산화아파타이트(Hydroxyapatite, HA; $Ca_{10}(PO_4)_6(OH)_2$)는 결정학적, 화학적으로뼈의 무기질 성분과 거의 유사하여 실제 체내에 들어가면 주위 뼈와 화학적 반응을 하여 단단한 결합을 이루는 생체활성(bioactive)을 가진 것으로 알려져 있다. 또한, 인산삼칼슘(Tri-Calcium Phosphate, TCP; $Ca_3(PO_4)_2$)은 체내에 이식 시 체액에 용해되어 신생골을 유도하는 생체흡수성(bioresorbable) 세라믹스로 알려져 있다. 상기 2종류를 포함한 인산칼슘계 화합물은 우수한 생체친화성에도 불구하고 역학 특성이 낮아, 하중을 거의 받지 않는 분야에만 사용되고 있는 실정이며, 하중을받는 분야(load-bearing part)에 적용하기 위해서는 고강도/고인성의 세라믹스와의 micro-composite이나 인산칼슘계화합물을 금속 표면에 코팅한 macro-composite의 형태로 사용되고 있다. 하중을 거의 받지 않는 분야, 예를 들어 치아 결손부를 보충할 dental shot과 같은 인산칼슘계 다공질 골충전재의 경우에도 취급 시 잘게 파손되는 문제점이 있어 치과의사들이 어려움을 호소하고 있는 실정이다. 본 연구에서는 HA, TCP의 역학특성을 증진시키고자 소결 공정 제어를 통하여 미세조직을 변화시켰으며, 미세조직 변화에 따른 세포반응성을 골포세포주를 이용하여 평가하였다.

• Applied Chemistry for Engineering
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• v.16 no.1
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• pp.117-122
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• 2005

The aim of this study was to evaluate the effect of tertiary amine photo-accelerator on the dental properties of visible light-activated, polymeric, dental restorative composites (PDRC) through the measurement of mechanical and esthetic properties. The surface of barium silicate was hydrophobically treated to improve the interfacial behavior with the acrylic resin matrix. Camphorquinone was adopted as a photo-initiator with 0.5 wt% based on the resin matrix. It was discovered that the dental properties of PDRC were primarily dependent on the chemical structure rather than the added content of photo-accelerator.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.4
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• pp.659-664
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• 2004

Dens invaginatus is a developmental variation resulting from invasination of the tooth crown of root before calcification. Teeth most affected are maxillary lateral incisors. The malformation shows a broad spectrum of morphologic variations and frequently results in early pulp necrosis. Root canal therapy may present severe problems because of the complex anatomy of the teeth. So, the early diagnosis of such malformation is crucial and a preventive approach has been recommended. This report describes three cases of dens invaginatus treatment.

• Journal of dental hygiene science
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• v.15 no.5
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• pp.673-678
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• 2015

The purpose of this study was to evaluate the reliability and accuracy of linear measurements in digital models compared to master model. A master model (ANKA-4; Frasaco GmbH, Tettnang, Germany) with the prepared upper full arch tooth was used. Four linear measurements were recorded between landmarks, directly on the master model and the digital models by a single examiner. Measurements were made with a digital caliper from manual model and with the software from the virtual models. The t-test for paired samples and intraclass correlation coefficient (ICC) were used for statistical analysis. The measurement of two methods showed good reliability. The mean differences between master and digital model were 0.06~0.12 mm. These in vitro studies show that accuracy and reliability of the digital impression is similar to that of the gold standard. Therefore digital impression was also considered to be a acceptable for placement clinically.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.4
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• pp.330-336
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• 2000

Effects of microstructure and indentation stress on fracture behavior of glass-infiltrated alumina composite for dental restorative application were investigated by the Hertzian and Vickers indentation method. Indentation stress-strain curve of glass-infiltrated alumina has showed the quasi-plastic behavior - deviation from linearity at high stress and the classical Hertzian cone crack, which could be confirmed the subsurface damage micrographs using bonded-interface specimen technique. The indentation stress-strain curves for the starting preforms are strongly dependent on porosity and microstructure of the preforms. On the other hand, the curves for the infiltrated composites are relatively insensitive to these factors. The failure of composite is originated at quasi-plastic deformation region. Damage and fracture behavior due to Hertzian stress field is theoretically examined, so that the indentation stress field plays a great role in material degradation. After Hertzian indentation annealing processing changes fracture behavior of alumina composite, so that stress field in material is healed through annealing.

• Journal of the Korean Ceramic Society
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• v.41 no.2
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• pp.143-150
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• 2004

Biaxial flexure strength (ball-on-3-ball) and fracture toughness (indentation microfracture) of heat-pressable glass-ceramics for dental use were investigated in this study. Crystal phase and microstructure of glass-ceramics were analyzed by XRD. SEM, and TEM. Crack propagation in specimens was not effectively arrested by dispersed crystalline particles. However, higher degree of crystallization probably contributes to strengthening of glass-ceramics. Better clinical reliability can be expected from lithium disilicate glass-ceramic because of its significantly higher biaxial flexure strength and fracture toughness.

• The Journal of Korean Academy of Prosthodontics
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• v.50 no.1
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• pp.10-20
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• 2012

Purpose: The purpose of this study was to investigate the stress distribution in mandibular implant-supported overdentures and tooth-supported overdentures with telescopic crowns. Materials and methods: The assumption of this study was that there were 2, 3, 4 natural teeth and implants which are located in the second premolar and canine regions in various distributed conditions. The mandible, teeth (or implants and abutments), and connectors are modeled, and analyzed with the commercial software, ANSYS Version 10.1. Stress distribution was evaluated under 150 N vertical load bilaterally on 3 experimental conditions - between canine areas, canine and $2^{nd}$ premolars, 10 mm posterior to $2^{nd}$ premolars. Results: Overall, the case of the implant group showed more stress than the case of the teeth group in stress distribution to bone. In stress distribution to superstructures of tooth and implants, there was no significant difference between TH group and IM group and the highest stress appeared in TH-IV and IM-IV. The stress caused from bar was much higher than those of implant and tooth. TH group showed less stress than IM group in stress distribution to abutment teeth and implant. Conclusion: The results shows that it is crucial to make sure that distance between impact loading point and abutment tooth does not get too far apart, and if it does, it is at best to set abutment tooth on premolar tooth region. It will be necessary to conduct more experiments on effects on implants, natural teeth and bone, in order to apply these results to a clinical treatment.

• Journal of dental hygiene science
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• v.8 no.2
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• pp.89-96
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• 2008

Effects of sodium fluoride exposure on the amelogenesis during fetal formation were investigated using 11 days rat incisor of control group and two experimental groups. According to results of morphological analysis using an electron microscope, enamel organ in the rat incisor consisted of presecretory, secretory, and maturation zone, especially maturation zone had ruffle-ended ameloblasts (rAB) that additionally supply inorganic ions and smooth-ended ameloblasts (sAB) that remove water and organic compounds. Such a histological composition was same in fetal and adult rats. According to experimental results using calcein (green fluorescence) in order to reveal the modulation cycle of ameloblast, modulation cycle of experimental group decreased on an average one time than control group, as increase of density of sodium fluoride indicated that thickness of smooth-ended ameloblast decreased. Also ratio of thickness on sagittal total length of sAB increased than rAB in experimental groups than control group. In total length of teeth, an injected 100 ppm sodium fluoride group was similar control group but as injected 200 ppm group became short. In experimental group, thickness of sAB and rAB became narrow to the tip of cutting edge. According to concentration of sodium fluoride grows, the modulation cycle and total length of teeth were decreased, finally it prevented teeth growth.