• 치과방사선
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• 제22권1호
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• pp.87-94
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• 1992

The purpose of this study was to evaluate the effect of scatter radiation to dental x-ray film with long time-exposure in the different structures of the tooth, by using pinhole camera. For this study, pinhole camera, skull with tooth, and pocket dosimeter were used. The radiation with 70 and 90kVp and exposure time (minimum: 2.5 min., maximum 10 hrs.) was projected to the film in the pinhole camera. And density of the obtained x-ray film was measured with densitometer. In the intra-oral film taking, the amount of exposure of the scatter radiation affecting the thyroid gland area was measured with the dosimeter at the thyroid gland. The density of radiographs was compared in radiation projected with or without the metal cone of dental machine. The effect of the back scatter radiation to the film was also evaluated when the lead foil was removed. The obtained results were as follows: 1. A pinhole camera was a valuable device for locating the source of x-ray. 2. The scatter radiation affected the dental x-ray film when the radiation source was exposed. more than 5 hours'. In that case, the density of the scatter radiation could be observed visually. 3. The scatter radiation caused by short exposure of dental radiation didn't affect the diagnostic quality of the dental x-ray film. 4. The differences of densities between the tooth and the soft tissue according to exposure time showed 0.16 in 5 hours' exposure & 0.17 in 10 hours' exposure at 70 kVp & 0.12 in 5 hours' exposure & 0.13 in 10 hours' exposure at the 90kVp. 5. The differences of densities between the tooth and the soft tissue according to kVp showed no difference between 5 hours' exposure of tooth at 70 kVp and soft tissue at 90 kVp, but showed 0.05 high density in tooth when 10 hours' exposure at 90 kVp. 6. No difference of density was on radiographs taken with or without dental machine cone. 7. Back scatter radiation was recorded image of radiographs for only 3 min. 8. The amounts of the scatter radiation exposed to the thyroid gland in intraoral film taking were 1.12 mr in upper anterior, 0.55 mr in upper posterior, 2.75 mr in lower anterior, and 1.92 mr in lower posterior teeth.

• 대한치과보철학회지
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• 제41권3호
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• pp.369-378
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• 2003

Statement of Problem: Recently, resin cements have become more widely used and have been accepted as prominent luting cements. Current resin cements exhibit less microleakage than conventional luting cements. However, the constant contact with water and exposure to occlusal forces increase microleakage even in resin cements inevitably. Most bonding resins have been modified to contain a hydrophilic resin such as 2-hydroxyethylmethacrylate (HEMA) to overcome some of the problems associated with the hydrophobic nature of bonding resins. By virtue of these modifications, bonding resins absorb a significant amount of water, and there may also be significant stresses at bonding interfaces, which may adversely affect the longevity of restorations. Therefore the reinforcement of water stability of resin cement is indispensable in future study. Purpose: This study was conducted to examine the influence of water retention on microleakage of two resin cements over the period of 6 months. Materials and Methods: 32 extracted human teeth were used to test the microleakage of a single full veneer crown. Two resin cements with different components and adhesive properties - Panavia F (Kuraray Co., Osaka, Japan) and Super-Bond C&B (Sun Medical Co., Kyoto, Japan)- were investigated. The storage medium was the physiological saline solution changed every week for 1 month, 3 months, and 6 months. One group was tested after storage for 1 day. At the end of the each storage period, all specimens were exposed to thermocycling from $5^{\circ}C$ to $55^{\circ}C$ of 500 cycles and chewing simulation of 50,000 cycles, and then stained with 50% silver nitrate solution. The linear penetration of microleakage was measured using a stereoscopic microscope at ${\times}40$ magnification and a digital traveling micrometer with an accuracy of ${\pm}3{\mu}m$. Values were analyzed using two-way ANOVA test, Duncan's multiple range tests (DMRT). Results : Statistically significant difference of microleakage was shown in the 3-month group compared with the1-day or 1-month group in both systems (p<0.05) and there were statistically significant differences in microleakage between the 3-month group and the 6-month group in both systems (p<0.05). The two systems showed different tendency in the course of increased microleakage during 3 months. In Panavia F, microleakage increased slowly throughout the periods. In Super-Bond C&B, there was no significant increase of microleakage for 1 month, but there was statistically significant increase of microleakage for the next 2 months. For the mean microleakage for each period, in the 3-month group, microleakage of Super-Bond C&B was significantly greater than that of Panavia F. On the other hand, in the 6-month group, microleakage of Panavia F was significantly greater than that of Super-Bond C&B (p<0.05). Conclusion: Within the limitation of this study, water retention of two different bonding systems influence microleakage of resin cements. Further studies with the longer observation periods in viro are required in order to investigate water stability and the bonding durability of the resin cement. CLINICAL IMPLICATIONS Microleakage at the Cement-tooth interfaces did not necessarily result in the failure of the crowns. But it is considered to be a major factor influening the longerity of restorations. Further clinical approaches for decreasing the amount of microleakage are required.

• 한국식품조리과학회지
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• 제18권6호
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• pp.704-715
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• 2002

본 연구는 초등학교 아동의 식습관, 간식습관 및 섭식실태를 급식교와 비급식교에 따라 비교 분석함으로서 치아우식증 발생과의 관련성을 규명하고, 조사대상 아동들에게 영양교육 프로그램을 실시한 후 교육효과를 평가하고자 실시되었다. 1. 급식여부에 따른 식습관 조사 결과, 급식교 아동이 비급식교의 아동보다 아침식사의 규칙성, 식사속도, 식사량의 적당성 및 식사시간의 규칙성에 있어 바람직한 편이었고, 고기나 생선, 해조류, 우유나 유제품의 섭취정도도 약간 높게 나타나 급식을 통하여 올바른 식생활 태도가 형성되는 것으로 보여졌으며 전반적으로 영양교육 후 식습관에 있어 긍정적인 변화를 나타내 영양교육의 효과가 있었음을 알 수 있었다. 2. 카라멜, 초콜렛 및 사탕류, 비스켓류 등의 치아우식유발 지수가 높은 우식성 식품을 간식으로 자주 섭취하고 있었고 충치유발 요인 인지 시 간식을 덜 사먹겠다는 아동이 급식교에서 다소 많았으며, 물리적 청정작용을 하는 껌을 간식으로 씹는 경우는 1주일에 2∼3회가 가장 높게 나타났다. 또한 영양교육 후 치아우식에 영향을 줄 수 있는 시간인 저녁 식사 후에 간식을 먹는 아동과 TV 광고로 인해 간식을 선택하는 아동의 비율이 낮아졌으며, 세정식품인 채소와 과일, 단백질, 해조류, 우유 또는 유제품의 섭취는 교육 후 약간 증가하였다. 3. 치아우식과 관련이 있는 당질군을 제외한 모든 식품군에서 비급식교 아동보다 급식교 아동의 섭취횟수가 높게 나타났으며 1인 1일 우식성 식품의 평균 섭취 횟수는 평균 5.04회였고, 고체식품보다는 액체식품으로 섭취하는 횟수가 다소 높았다. 치아표면에서 청청작용을 하여 치면세균막의 형성을 감소시켜 우식증을 예방하는 세정식품의 평균 섭취 횟수는 1인 1일 기준식품 표준섭취 횟수보다 높은 9.33회로 나타났다. 1인 1일 우식발생 가능 시간은 100.9분이었는데, 액체 식품의 우식발생 가능 시간은 56.2분으로 44.6분인 고체 식품에서 보다 높게 나타났다. 이상의 결과에서 식습관이 치아우식발생과 밀접한 관계를 가지고 있으므로 초등학교 아동에 있어 치아우식을 유발할 수 있는 간식의 섭취를 줄이되 우식성 식품을 간식으로 섭취한 후에는 잇솔질을 반드시 실시하도록 하며 정규식사에서 치아를 보호하는 세정식품의 섭취에 대한 영양교육이 지속적이고 단계적으로 꾸준히 이루어져야 한다고 본다.