• The Korean Journal of Nuclear Medicine
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• v.27 no.2
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• pp.293-297
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• 1993

Chitosan is a natural chelating agent. It is derived from chitin which is a cellulose-like biopolymer distributed widely in nature, expecially in shellfish, insects, fungi, and yeast. The purpose of the present study is to investigate whether orally given water soluble chitosan can eliminate intraperitoneally injected radiostrontium (Sr-85) in mice. Water soluble chitosan and usual food was mixed as 10:90 by weight. The mixed food were fed for 60 (group 1) or 90 days (group 2). No chitosan was given to the control group. Each group consists of 5 mice. Sr-85 ($0.2{\mu}Ci$) was intraperitoneally injected after completion of prefeeding of usual or mixed food. The same food was given for more 5 days. The animals were sacrificed at the 6th day. Isolated spines, skulls, femurs, tibias, teeth, and tails were counted by a gamma counter. The retention of Sr-85 in bones was significantly lowere in the prefeeding groups (p<0.01). It was lowest in the 90 day prefeeding group. Therefore, prefeeding of water-soluble chitosan was effective on the removal of intraperitoneally injected radiostrontium.

• The korean journal of orthodontics
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• v.37 no.5
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• pp.376-385
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• 2007

Esthetic brackets which resemble the color of natural teeth have been widely used. But the frictional resistance of ceramic brackets, a typical esthetic bracket, is greater than that of metal brackets. The purpose of this study was to measure the frictional resistance of the new calcium phosphate brackets (CPB) which were recently developed and to evaluate its clinical usability by comparing the frictional differences of CPB with metal brackets and metal slot inserted ceramic brackets. Methods: Experimental groups were CPB (Hyaline II, Tomy, Tokyo, Japan), metal bracket (Kosaka, Tomy, Tokyo, Japan) and metal slot inserted ceramic bracket (Clarity, 3M Unitek, Monrovia, CA, USA). All of the brackets had 0.022-inch slot sizes. The brackets were tested with $0.019\;{\times}\;0.025$ inch stainless steel wire (3M Unitek, Monrovia, CA, USA). A biologic model was used to simulate the situation which would occur during orthodontic treatment with fixed appliances. Retraction force was applied at a speed of 5 mm/min for 30 seconds. The frictional resistance was measured on a universal testing machine (Instron 4467, Instron, Norwood, MA, USA). Results: CPB showed significantly higher friction than metal brackets (p < 0.05) and lower friction than metal slot inserted ceramic brackets (p < 0.01). Conclusions: CPB can be considered to be a useful orthodontic esthetic bracket with respect to frictional resistance, as its friction is remarkably lower than that of metal slot inserted ceramic brackets.

• The Journal of Korean Academy of Prosthodontics
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• v.38 no.2
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• pp.242-254
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• 2000

Accurate impression is very important to achieve desirable prosthesis and there are many factors in taking a good impression. For example, types of impression material, types of impression tray, impression taking methods and so on. Recently individual tooth tray technique is accepted as obtaining good impression that can be applied to multiple abutment impression, heavy salivated patient, to minimize the effect of natural teeth s undercuts and to reduce pain during cord packing procedures. The purpose of this study was to compare the accuracy according to materials and forms of the individual tooth tray which is clinically applied nowadays. Used materials in experiment were divided into 3 types (acrylic resin. $Futar^{(R)}$ occlusion. $Blu-mousse^{(R)}$) and forms were divided into 2 types (forming occlusal vent hole or not and forming marginal vent space or not). Stone master model from impression body and metal master model were measured by $X-PLAN360d^{(R)}$ to compare occlusal surface discrepancy and marginal discrepancy. The results were as follows: 1. In comparison of occlusal surface discrepancy and marginal discrepancy according to materials, groups with three materials showed no statistical difference 2. In comparison of occlusal surface discrepancy and marginal discrepancy according to occlusal vent hole, groups with occlusal vent hole showed significantly less marginal discrepancy than groups with no occlusal vent hole(p<0.05). 3. In comparison of occlusal surface discrepancy and marginal discrepancy according to 0.5mm-marginal-vent-space, groups with no 0.5mm-marginal-vent-space showed significantly less marginal discrepancy than groups with 0.5mm-marginal-vent-space (p<0.05). In summary these results suggest that individual tooth tray made of 3 types of materials with occlusal vent hole and individual tooth tray made of acrylic resin with no marginal vent space showed good accuracy of impression. In addition, individual tooth tray which is made of bite registration materials may be more useful because of advantage in facility and timesaving aspect of fabrication.

• Journal of the Korean Academy of Esthetic Dentistry
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• v.22 no.1
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• pp.47-55
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• 2013

There have been a great number of developments in clinical techniques and dental materials in dentistry to date. Looking at these developments, while it could be seen that functional elements such as mastication were prioritized rather than aesthetic aspect in the past, aesthetic needs of patients have steadily increased over time and accordingly the aesthetic has become considered a priority in the development of dentistry. Although the first to be considered in discussing the aesthetic in clinical dentistry will be the white aesthetic that is the tooth part of prosthesis, the pink aesthetic that refers to the harmony of such prosthesis with gingiva can be an important consideration not to be ignored aesthetically. However, the harmony with the gingiva often cannot be obtained only by the beautiful prosthesis, and in particular, the pontic and implant areas have poor conditions to achieve the gingival (pink) aesthetic due to the absorption of alveolar ridge compared to natural teeth. Among the most important elements of the gingival aesthetic are the gingival level and the interproximal papilla height. It is very difficult to make the gingival aesthetic in the case of insufficient alveolar ridge, and the recovery of ridge volume and contour is necessary in order to overcome this condition. To this end, the most widely used method is the "connective tissue graft". Many techniques of the connective tissue graft have already been introduced for the ridge augmentation, and each technique has different purposes, and advantages and disadvantages. Rather, due to the excessive amount of techniques, there is confusion about selecting the right technique at a certain time. However, the goal is clear. Ways to increase the success rates must be found, and at the same time, a more favorable way to the gingival aesthetic is to be chosen. Thus, in this study, considerations for the gingival aesthetic that makes harmony and the techniques to achieve it are discussed.

• Journal of Periodontal and Implant Science
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• v.25 no.2
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• pp.279-289
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• 1995

The most important object of periodontal treatment is the perfect regeneration of destructed periodontal tissue. The healing of periodontal lesion is affected by several cells & factors, which result in formation of long juntional epithelium, root resorption, bony ankylosis or connective tissue attachment. And ideal healing is enhanced by epithilial exclusion or periodontal ligament cell activation. In this investigation, I studied the effect of Zizyphus Fructus extract which enhances biologic activity& collagen synthesis, on the chemotaxis & cell nature. The cells were obtained from interdental area & middle third area of the freshly extracted teeth for the orthodontic purpose. And they were fully incubated in${\alpha}-MEM$ solution containing $100{\mu]g/ml$ penicillin & $100{\mu]g/ml$ streptomycin followed by 6 generation incubation. The test cells were collected by trypsin-EDTA & centrifuge in the fully incubated cells, counted by Hernacyotmeter, incbated $5{\times}10^5/ml$ cells for 24 hours, re-incubated 24 hours in media containing natural extract and photographed. The cells were incubated for 4 hours in 48 well microchemotaxis chamber bisecting upper & lower chamber by 8ug/m pore polycarbonate membrane coating 5mg/ml gelatin solution. The migrated cells in microscope were counted, which meaned cell chemotaxis activity. The study had shown that the morphology of cell was spindle-shaped as the control group, and the subextract test groups were not significantly different. In gingival fibroblasts, the chemotaxis effect of PDGF was statistically significant compared to control group. The Zizyphus Fructus extract was more or less enhanced chemotaxis effect and in $1{\mu}g/ml$ concentration the chemotaxis effect was slightly elevated compared with $10{\mu}g/ml$ concentration. But, among the subextracts, it was not significantly defferent. In PDL cells, the chemotaxis effect of PDGF in statistically significant, and the zizyphus Fructus extract had shown the enhanced effect. The effect was slightly higher in $1{\mu}g/ml$ concentration than 10g/ml concentration,and no significance among the subextracts.

• The Journal of Korean Academy of Prosthodontics
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• v.58 no.1
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• pp.58-66
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• 2020

Implant-Assisted Removable Partial Dentures (IARPDs) treatment is being performed in a fully edentulous patient using implant surveyed prosthesis as an abutment. Implant-supported prosthesis as an abutment of IARPDs is classified into screw-retained and cement-retained type according to the retention type, and each has advantages and disadvantages. The EZ crown system (Samwon DMP, Yangsan, Korea) has a cylinder combined with abutment, and the nickel-titanium spring in this cylinder provides a constant force on the zirconia ball to obtain retention in EZ crown system. In this patient, the natural abutment teeth of the mandibular overdenture was hopeless. We planned implant assisted removable partial denture using anterior implant surveyed prosthesis considering functional and esthetical rehabilitation, cost and patient's needs. When fabricating IARPDs using implant as abutment, we could compensate for the shortcomings of existing implant-supported prosthesis retention type and made the design of removable partial denture easy due to using EZ crown system.

• Journal of the korean academy of Pediatric Dentistry
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• v.38 no.3
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• pp.262-269
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• 2011

Ameloblastic fibroma is rare true benign mixed odontogenic tumor. Most of these tumors occur in the posterior region of the mandible under 20 years of age. It develops generally associated with unerupted tooth and grows slowly on the surface of alveolar bone, therefore interferes normal tooth eruption. These lesions rarely showing a little bony expansion, are usually asymptomatic and are discovered incidentally on routine dental exam. It is similar to amleoblastic fibroodontoma and ameloblastic fibrodentinoma clinically and roentgenographically but represents no dental hard tissue formation histologically. Enucleation and curettage of surrounding bone are generally recommended options for treatment. Even though there are some reports of recurrence and malignant transformation and more aggressive treatment options like block resection are suggested sometimes, but in most cases, recurrence is unusual because it is well encapsulated and easily separated from adjucent bony socket. In these cases, we did conservative treatment such as enucleation and curettage to the patients who were visited for ameloblastic fibroma associated with delayed eruption of lower first molar. After regular check-ups, we found relatively natural eruption process of combined teeth.

• Journal of dental hygiene science
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• v.17 no.4
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• pp.358-367
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• 2017

The purpose of this study was to evaluate the influence of water infiltration and flexural strength changes in dental porcelain with glazing treatment. The block specimens were prepared as experimental materials, using feldspar type commercial dental porcelain; then, these were fired at $940^{\circ}C$ for 1 minute. The fired specimens were polished with a dimension of $40{\times}5.5{\times}5mm$. The specimens were distributed to two experimental groups: with and without glazing treatment specimens (n=5), and they were immersed in a solution of pH 7 for 3, 7, and 20 days at $40^{\circ}C$ after fabrication. To evaluate the flexural strength changes with water infiltration treatment in specimens with and without glazing, the 3-point flexural test was performed, using a universal testing machine until failure occurred. Starting powder and fired specimens consisted of amorphous and leucite crystalline phase. The Vickers hardness of fired specimens was more than 1.6 times higher than that of the enamel of natural teeth. According to porosimeter results, the specimens without glazing treatment exhibited a porosity of about 14.7%, whereas the glazed specimens exhibited the lowest porosity at about 1.1%. The average flexural strength of glazed specimens was higher than the flexural strength of specimens without glazing treatment (p<0.05). The flexural strength of all specimens with and without glazing treatment deteriorated with accelerated aging in the solution. In addition, significant differences between these two treatment groups were observed in all of the specimens treated at various water infiltration periods (p<0.05). The exposure of internal pores and micro-cracks in the surface due to polishing of the fired specimens influenced mechanical behaviors. Especially, the flexural strength in specimens without glazing treatment has shown significant degradation with the infiltration of water. Therefore, this study suggests that glazing processes can improve mechanical properties of dental porcelain.

• Journal of Korean society of Dental Hygiene
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• v.15 no.4
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• pp.705-711
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• 2015

Objectives: The purpose of the study is to evaluate the effect of continuing dental care program by elementary school dental clinic in Gimcheon from 2008 to 2013. Methods: The subjects were experimental group of 152 students from three elementary schools having dental clinics and control group of 136 students from three elementary schools of no dental clinics. The six dentists in Gimcheon community health center carried out the regular dental checkups in the elementary schools and four dental hygienists recorded the dental examination results. After receiving WHO dental survey guideline education, the examiners used dental mirror and dental probe under the natural light. The contents of the survey included dental caries in the deciduous and permanent teeth, malocclusion, remaining ratio of sealant, treatment, and follow up. Results: DFT index by grade showed that 3.71 in experimental group and 4.56 in control group and it was remarkable in the 3rd grade. Thus. DFT index in the experimental group was lower than that of control group (p<0.05). DT index by grade was 0.63 in experimental group and 1.28 in control group marked in the 6th grade. DT index in the control group was higher than that of the experimental group (p<0,001). DFT index and DMFT Index by grade showed no significant difference between the control group and the experimental group. DFT and DMFT Index of the control group in the 3rd and 6th grade were lower score than those of experimental group. DFT and DMFT index in the third and 6th grade showed no significant difference between the control group and the experimental group. The remaining ratio of the sealant was 4.89 experimental group in the 6th grade. The remaining ratio of the sealant in the experimental group was higher than that in the control group. Conclusions: The continuing dental care program in the elementary school is very effective method in the treatment of oral disease in the elementary school children. The oral health care and prevention for the elementary school children should be implemented and carried out continuously.

• The Journal of Korean Academy of Prosthodontics
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• v.56 no.3
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• pp.258-268
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• 2018

Purpose: This study systematically examines literatures on the suitability of prostheses and accuracy of obtained impressions to see if digital impressions using intraoral scanners can replace traditional impressions. Materials and methods: A MEDLINE/PubMed search and manual search was performed for studies written in English about accuracy of digital impression published in dental journals from August 1, 1997, to July 31, 2017. Depending on criteria, the data for the selected articles were independently organized into standardized spreadsheets by 2 reviewers. Results: Among the total 35 studies met the inclusion criteria, there were 26 studies comparing the suitability of prostheses, and 9 studies comparing the accuracy of impressions through scan data without prostheses. Most studies used prostheses to compare the accuracy of impression techniques. Conclusion: This review suggests that making single crown or mesio-distally short prostheses with digital impressions is clinically reliable in natural teeth. However, there is still a limit to making mesio-distally long prostheses with digital impressions from the lack of related studies. Digital impression cannot fully replace traditional impressions in implant prostheses yet.