• Journal of the korean academy of Pediatric Dentistry
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• v.36 no.2
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• pp.227-236
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• 2009

The purpose of this study is to examine the acidity of beverages that are sold for children in the market and to estimate by experiment the degree of the enamel erosion of deciduous teeth that is attributed to the beverages. The pH value of children beverages among top sale list in Seoul and Gyeonggi province were measured. And 7 beverages with the pH value of 3.5 or lower were selected. The enamel erosion of deciduous teeth by the children beverages for 1, 5, 10, and 30 minutes respectively was examined. The results were as follows: 1. The acidity of most of the children beverages examined in this study was the pH level of 5.5 or lower that can cause the tooth erosion. 2. The microhardness value of the enamel of deciduous teeth was lower as exposing it to children beverages. The reduction of surface microhardness value was significant from 1 minute after the exposure, and the reduction was continuously observed until 30 minutes has passed. 3. The higher the acidity of beverages, the larger the reduction in microhardness value caused after the exposure of 30 minutes to the beverages. There was no significant relation between the acidity of beverages and the reduction rate of surface microhardness value. The other factors such as calcium, phosphorus, and fluorine or buffering of the beverages may affect the enamel erosion.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2013.05a
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• pp.125-125
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• 2013

기계부품 및 자동차부품 등의 내마모나 내피로성의 향상을 위한 표면처리로서 고주파처리, 침탄처리, 질화처리 등이 사용되고 있다. 최근에는 변형을 최소화 함으로써 후가공을 생략할 수 있는 질화처리가 주목받고 있다. 질화처리종류로는 염욕질화나 가스질화법이 사용되고 있으나, 이들에 비해 환경오염 및 공해가 적고 인체에 무해한 플라즈마 연질화법이 사용되고 있다. 플라즈마 연질화 기술은 IT기기의 제품에 적용되는 표면경화의 공정개발은 미비한 실정이다. 마이크로 구동 요소 부품중의 하나인 Leadscrew는 이송장치를 구성하는 핵심 부품으로 IT기기의 정밀 이송 및 구동제어에 사용되는 핵심 부품으로 사용되고 있으며, 리드스크류의 소재인 SWCH1018A(냉간압조용강선)은 표면 경도가 낮고 변형이 쉽기 때문에 표면 경화를 위한 플라즈마 연질화 기술을 이용하고자 했다. 본 연구는 플라즈마 연질화 공정을 적용한 시편의 표면경도를 높혀주고 변형을 최소화 할 수 있는 공정을 확인하는 것이다. 공정변수를 변화 시키면서 얻어진 시편의 표면미세 구조를 미소경도측정, XRD, SEM분석을 통하여 확인하였으며, 이를 통해 시편 표면경도를 높여주는 공정 조건을 도출하였다.

• Proceedings of the KAIS Fall Conference
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• 2005.05a
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• pp.55-57
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• 2005

기존의 장신구 은제품은 무르고 주조공정 특유의 미세한 표면결함을 가져서 착웅 중 쉽게 변색되는 문제가 있었다. 본 연구에서는 내식성을 향상시키기 위해 $92.5\%Ag-6.5\%Cu-1\%Zn$의 삼원계 은합금을 기초 소재로 해서 반지장신구를 상정하여 기존의 주조공정으로 대략의 형태를 만들고 금형과 유압프레스로 성형 가압시켜서 적극적으로 주조 시에 발생한 미세기공을 제거하고 결정립을 미세화하여 표면경도와 밀도를 향상시켰다. 선반가공과 미세연마를 실시하여 내식성이 향상된 표면과 기존 주조공정에 비해 3배 이상 향상된 경도를 가져서 스프링백 효과에 의해 귀보석을 세팅할 수 있는 개선된 텐션형 은장신구 공정을 개발하였고 이때의 최적 성형 정도를 확인하였다.

• Journal of the korean academy of Pediatric Dentistry
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• v.37 no.1
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• pp.82-90
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• 2010

This study examined the effect of adhesive tape supplemented with sodium fluoride on the prevention of dental erosion in vitro. Sound bovine tooth samples were selected and divided randomly into the following 4 groups according to the material treatments: group 1, APF gel; group 2, fluoride varnish; and groups 3 and 4, fluoride tape supplemented with 5% NaF in either a methyl cellulose or poly vinyl acetate carrier, respectively. All specimens were submitted to alternate cycles of acid exposure in a cola beverage (pH 4.3) and artificial saliva for $6\;{\times}\;5\;min/day$ over a 5 day period. The micro-hardness was recorded each day and the lesion depth was measured after 5 days. The micro-hardness of the experimental sides of groups 2, 3 and 4 were significantly higher than that of their control sides and the experimental side of group 1 during the experimental period (p<0.05) except on the 5th day. The enamel surfaces of treatment groups 2, 3 and 4 showed significantly higher resistance to mineral loss in terms of the erosion depth (p<0.05) than group 1 and their control sides. There was no statistically significant difference among group 2, 3 and 4, indicating that the fluoride varnish and tapes produce similar results. Fluoride adhesive tapes are effective in reducing the progression of erosion and can be recommended for young patients who are more susceptible to dental erosion.

• Journal of Convergence for Information Technology
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• v.9 no.7
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• pp.159-167
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• 2019

This study aimed to evaluate the effects of oral rinsing solution on the color stability, surface microhardness and surface roughness change of composite resin. In this in-vitro study, 80 disc-shaped specimens were fabricated of Filtek P60 and Filtek Z250(A2 shade). The samples of each group were randomly divided into eight subgroups (n=10). The baseline color values ($L^*$, $a^*$, $b^*$) of each specimen were measured according to CIE LAB system using a colorimeter. After baseline color measurements, the control samples were immersed in distilled water and the test groups were immersed colorless, green and purple mouthrinses three times a day for thirty minutes. This process was repeated for two weeks. Green and purple oral rinsing solutions displayed color, microhardness and roughness change of all composite resin after immersion in the mouthrinses. Therefore, prescription of oral rinsing solution for a minimum of two weeks is a common practice, which may cause discoloration of aesthetic composite restorations of patients.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.05b
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• pp.118-122
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• 1997

차세대 원자력발전소 증기발생기 전열관 재료로 채택된 니켈기저합금으로 기존 전열관 재료인 인코넬600에 비해 고온 고압 조건에서 응력부식균열에 강한 장점을 가진 합금인 인코넬690 시료에 최대 에너지 120 keV의 질소 이온빔을 조사하여 이 재료의 기계적 특성 변화를 관측하였다. 특성 시험으로는 표면 경화를 관찰하기 위한 미세 경도 시험을 수행하여 미세 경도 증가를 확인하였다 아울러 표면 경화가 피로 특성에 미치는 영향을 관찰하기 위해 피로 균열 전파 시험을 수행하여 이온 주입으로 인한 표면 경화가 피로 균열 전파를 촉진시킴을 관찰하였다.

• Proceedings of the KAIS Fall Conference
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• 2003.06a
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• pp.83-86
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• 2003

SKD11은 자이로 펌프의 로타와 붓싱 재질로 사용되는데, 자이로펌프는 임펠러의 회전이 없고 원판의 기울기 운동으로 흡입과 토출을 반복하는 고압용적식 펌프이다. 이 펌프의 내구성을 향상시키기 위하여 우수한 내압성과 내마모성을 갖는 재질선정이 요구한다. 따라서 현재 가장 널리 사용되고있는 SKD11에 심냉처리를 통하여 미세조직의 개선을 수행하였고, 가스질화처리에 의한 표면경화로 내압성과 내마모성을 증가시키고자 하였다. SKD11의 미세조직 변화를 조사하기 위하여 광학현미경과 X-선 회절기를 사용하여 미세조직 관찰과 상변화를 조사하였으며, Rockwell 경도기틀 사용하여 각 변수에 따른 경도변화를 조사하였다. 연구 결과 기지조직은 모두 마르텐사이트로 나타났으며, 이 이외에 각각의 조건에 따라 크롬탄화물, PFZ, 잔류오스테나이트가 확인되었다. SKD11을 액화질소로 냉각한 후 500℃에서의 템퍼링으로 가장 큰 경도값을 얻을 수 있었다. 또한 가스질화처리에 의하여 표면경도를 크게 증가시킬 수 있었다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2013.05a
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• pp.88-91
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• 2013

현재 활용되고 있는 침탄질화기술과 QT + 저온 플라즈마 침질탄화 기술로 소재의 표면특성을 향상시켜 상대적인 비교를 위해 미세조직, 경도, XRD, GDS 및 Wear Test를 실시하였다. 비교결과 확산층에서의 경도는 침탄처리한 시편이 상대적으로 높았지만, 표면경도 및 Wear Test의 경우 QT+플라즈마 침질탄화처리한 시편이 더 좋은 결과를 보였다.

• Journal of dental hygiene science
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• v.10 no.4
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• pp.295-300
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• 2010

The aim of this study were to elucidate effects of fluoridated bleaching agents and post-treatment fluoride application on the color and microhardness of enamel surface. Twenty freshly extracted human adult molar were each sectioned into halves, the specimens divided and treated according to four experimental groups: 1, untreated controls: 2, treatment with 10% carbamide peroxide (CP) bleaching agent; 3, treatment with 10% CP containing 0.11% fluoride; 4, treatment with 10% CP followed by a 0.9% sodium fluoride gel application. Group 2-4 were compared with the baseline data. treated 8 h per day for 14 days then immersed in distilled water for 2 weeks. Changes in enamel color and microhardness were evaluated on Days 7 and 14. All the bleached enamel specimens revealed increased whiteness and overall color value. Groups 2 and 4 showed significantly decreased enamel microhardness compared to their baseline. The specimens treated with fluoridated bleaching agents showed relatively less reduction in enamel microhardness than those treated with nonfluoridated agents during the bleaching treatment. The addition of fluoride did not impede the tooth whitening. The fluoridated bleaching agents reduced the microhardness loss of enamel.

• The Journal of the Korea Contents Association
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• v.12 no.1
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• pp.353-360
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• 2012

The purpose of this study was to evaluate tooth color and microhardness after 15% carbamide peroxide(CP) bleaching treatments with/without potassium nitrate and fluoride(PF), which were used home bleaching. Thirty tooth specimens were obtained from thirty premolar and were randomly divided into three groups: 1, untreated controls(Distilled water): 2, treatment with 15% CP bleaching agent; 3, treatment with 15% CP bleaching agent (contained 3% potassium nitrate and 0.11% fluoride). All groups were treated 6h per day for 14 days then immersed in distilled water. Changes in enamel color were evaluated on Baseline and Day 14. Microhardness were evaluated on Baseline, Days 7 and 14. All the bleached enamel specimens revealed increased whiteness without control group. Groups 2 and 3 showed significantly decreased enamel microhardness compared to control group. On Day 7, Groups 2-3 showed significantly decreased enamel microhardness compared to control group and respective baseline data. The percentage microhardness loss(PML) look at Day 7 and 14 for Group 1, respectively, there was little difference between 1.7 and 0.8. However, Group 2 was 21.9 and 3.5, Group 3 was 16.7 and 1.4 as a baseline and Day 7 were significantly different (p<0.05). The PML of group 2 was significantly highest than that of group 3 on Day 7. As a result, the data indicate that the addition of PF did not influence the whitening efficacy of the bleaching agent negatively. PF-containing bleaching agent reduce the percentage microhardness loss. PF-containing tooth bleaching your teeth with a whitening effect can be reduced by decreasing the hardness of enamel.