• Restorative Dentistry and Endodontics
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• v.24 no.2
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• pp.408-415
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• 1999

When a zinc-oxide eugenol type sealer was placed in root canals treated previously with calcium hydroxide, acceleration of its setting and the yellowish discoloration were observed clinically. The purpose of this study was to evaluate the properties of calcium hydroxide-eugenol compound. Some physical properties of calcium hydroxide-eugenol compound were compared with a manufactured zinc-oxide eugenol based root canal sealer, Tubli-seal$^{(R)}$ in terms of water solubility, water sorption, film thickness and microleakage. Solubility and water sorption were determined by the use of the method described in American Dental Association Specification(ADAS) no. 57. Ten samples of each material were prepared into disks 20mm in diameter and 1.5mm in thickness. The samples were immersed in 50ml of distilled water at $37{\pm}1^{\circ}C$ for 7 days. The samples were then removed and placed in a desiccator. The values for solubility and water sorption were calculated using differences between the weights of same sample. Film thickness was determined by the use of the method described in ADAS no. 57 too. A small quantity of mixed cement was placed between two glass plates of which thickness was measured previously. 15Kg loading was applied and total thickness of the glass plates and the cement film was measured. The thickness difference was recorded as the material's film thickness. Microleakage was determined with a dye penetration method. Experimental materials were placed between the dentin surface of bovine tooth and the acrylic rod. These units were immersed in Pelican ink (W-Germany) for three days. Dye-penetrated dentin surfaces of bovine tooth were measured using the NIB Image 1.60 Macintosh program. The results are as follows: 1. Water solubility value of calcium hydroxide-eugenol compound (20.98${\pm}$2.94%) was statistically higher than those of Tubli-seal$^{(R)}$(2.52${\pm}$0.49%)(p<0.05). 2. Water sorption value of calcium hydroxide-eugenol compound (59.72${\pm}$17.75%) was statistically higher than those of Tubli-seal$^{(R)}$(3.15${\pm}$0.76%)(p<0.05). 3. Film thickness value of calcium hydroxide-eugenol compound (0.36${\pm}$0.03mm) was statistically higher than those of Tubli-seal$^{(R)}$(0.12${\pm}$0.1mm)(p<0.05). 4. Dye penetration value after 3 days-immersion of calcium hydroxide-eugenol compound(57.63${\pm}$25.85%) was statistically higher than those of Tubli-seal$^{(R)}$(28.05${\pm}$23.46%)(p<0.05).

• Journal of the korean academy of Pediatric Dentistry
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• v.35 no.4
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• pp.619-627
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• 2008

The objective of this study was to compare the microleakage of five adhesive systems in the enamel and dentin of permanent teeth. Class V cavity preparations with occlusal margins in enamel and gingival margins in dentin were prepared on both buccal and lingual surfaces of 25 extracted human molar teeth. The tested adhesives were: Adper Scotchbond Multi-purpose Plus Adhesive (SM), Adper Single bond 2 (SB), Clearfil SE Bond (SE), Adper Prompt L-Pop (PL) and G-Bond (GB). The results were as follows: 1. At the enamel margins, PL showed the highest leakage value(0.85), and others showed values of SB(0.55), GB(0.50), SM(0.35) and SE(0.25) in decreasing order. There were statistically significant differences in PL vs. SM and PL vs. SE(p<0.05). 2. At the dentin margins, GB showed the highest leakage value(2.10), and others showed values of SE(1.45), PL(1.40), SB(1.05), SM(0.70) in decreasing order. There were statistically significant differences in GB vs. SB and GB vs. SM(p<0.05). 3. Dentin margins showed high dye penetration rate than enamel margins in all material tested groups and there were statistically significant differences for SE, PL and GB.

• Restorative Dentistry and Endodontics
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• v.31 no.5
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• pp.378-389
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• 2006

The purpose of this study was to compare the sealing ability of root canal obturation with or without the treatment of smear layer. Eighty extracted human teeth with one canal were selected Instrumentation was performed with crown-down technique. After instrumentation, root canals of the NaOCl group and NaOCl-6 group were irrigated with 3% NaOCl. EDTA group and EDTA-6 group were irrigated with 17% EDTA. Then all teeth were obturated using continuous wane obturation technique NaOCl group and EDTA group were immersed in methylene blue solution for 84hours. NaOCl-6 group and EDTA-6 group were immersed in methylene blue solution for 6months. The teeth were sectioned at 1.5 mn (Level 1), 3.0 mm (Level 2) and 4.5 mm (Level 3) from the root apex. The length of dye-penetrated inter-face and the circumferential length of canal at each level were measured using Sigma-Scan Pro 5.0. 1. The mean leakage ratio was decreased cervically. 2. NaOCl group showed higher mean leakage ratio than EDTA group at each level. But there was significant difference at level 1 only (p < 0.05). 3. NaOCl-6 group showed higher mean leakage ratio than EDTA-6 group at each level. But there was significant difference at level 1 only (p < 0.05). 4. NaOCl-6 group showed higher mean leakage ratio than NaOCl group at each level. But there was significant difference at level 1 only (p < 0.05). 5. EDTA-6 group showed higher mean leakage ratio than EDTA group at each level. But there was no significant difference. 6. In NaOCl group and NaOCl-6 group, scanning electron micrographs of tooth sections generally covered with smear layer. In EDTA group and EDTA-6 group, tooth sections showing the penetration of sealers to opened dentinal tubules. The results suggest that removal of smear layer was effective to reduce the apical microleakage of the root canal.

• Journal of the korean academy of Pediatric Dentistry
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• v.29 no.4
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• pp.592-599
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• 2002

Objective : The purpose of this study was to evaluate the effects of several light curing methods and several adhesives on the microleakage of composite resin restorations in primary teeth. Materials and methods : In 150 extracted human primary anterior teeth, O-shaped cavities were prepared in the labial surface ; the cavity diameter and depth were 1.6mm. The cavities were filled with light-activated composite resin, Compoglass. Four kinds of adhesives were used. Each filling materials were polymerized with three light cure methods. The restorations were polished using Sof-Lex discs(3M Co., USA). The samples were thermocycled 1,000 times between $5^{\circ}C$ and $55^{\circ}C$ with a 1-minute dwell time. Then, they were immersed in a 2% methylene blue solution(pH 7) for 12hours. Subsequently they were sectioned labio-lingually through the center of the restoration with a diamond saw at low speed with a water coolant, and evaluated by stereomicroscopy. Microleakage analyses were done, using scores from 0 to 4. Results : Results showed the least microleakage in Compoglass group(P<0.05). There were less microleakage in SBMP group among the adhesive groups, but no significant difference was observed(P>0.05). And there were no significant differences among the groups depending on curing methods(P>0.05).

• Journal of the korean academy of Pediatric Dentistry
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• v.35 no.2
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• pp.259-267
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• 2008

This in vitro study aimed to investigate the influence of flowable composite lining with different thicknesses on the marginal quality. One hundred twenty cavities, each preparated with proximal boxtype( 3mm of bucco-lingual width, 2mm of mesio-distal depth and gingival margin of 1mm supra-CEJ) were randomly dived into four groups. group I : Tetric ceram filling alone(control group) group II: 0.5mm thickness Tetric flow + Tetric ceram filling group III: 1.5mm thickness Tetric flow + Tetric ceram filling group IV: 2.5mm thickness Tetric flow + Tetric ceram filling The followings are the results: 1. Group II showed significantly less microleakage compared to group I(control group)(p<0.05). 2. There was no statistically significant difference between group III, IV and group I(p>0.05). 3. Group II showed significantly less microleakage compared to group III, IV(p<0.05). 4. There was microleakage more or less in all group. It was concluded that 0.5mm flowable composite lining improved cavity adaptation and marginal sealing.

• Restorative Dentistry and Endodontics
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• v.25 no.4
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• pp.543-549
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• 2000

Gutta-percha와 근관sealer를 사용한 근관 충전은 가장 많이 이용되고 성공률이 높은 방법이지만, 현재 사용되는 모든 근관sealer는 미세누출을 나타낸다. 따라서 더 효과적인 근관 폐쇄를 이루기 위한 재료 및 방법들이 연구되어왔다. 이중 상아질 접착제는 근관 충전재와 함께 사용되어 미세누출을 감소시키지만, 근관 내에 사용하기에 술식이 복잡하고 기술이 요구된다. 본 연구의 목적은 gutta-percha와 레진계 근관 sealer로 충전한 근관에서 self-etching primer를 미리 도포한 경우와 도포하지 않은 경우의 치근단 미세누출을 비교하고, self-etching primer를 도포함에 있어 근관 내에 적용하는 방법에 따른 미세누출을 비교하는 것이다. 또한 근관sealer와 상아질 계면을 주사전자현미경으로 관찰하여, 이 결과를 미세누출과 관련시켜보고자 하였다. 36개의 발거된 사람의 단근치에서 치관부를 절단, 제거하고 ProFile로 근관 형성한 후, 무작위로 선택하여 4개의 군으로 분류하였다. 1군에서는 주사기와 30게이지 주사 바늘로 self-etching primer를 근관 내에 적용하였고, 2군에서는 self-etching primer를 paper point에 적셔 근관 내에 적용하였다. 3군에서는 self-etching primer를 적용하지 않았다. 1, 2, 3군의 치아를 gutta-percha와 AH26 sealer를 사용하여 continuous wave 충전법으로 충전한 후 치근단공 주위 3mm를 제외한 치근변에 nail polish를 2회 도포하였고, 4군(음성 대조군)은 치근면 전체에 도포하였다. 1군과 2군에서 각각 2개의 치아는 주사전자현미경적 관찰을 위해 준비하였다. 모든 치아를 Methylene Blue 수용액에 48시간동안 침적, 수세한 후 치아 장축에 평행하게 양분하여 10배의 실물확대현미경 하에서 치근단 색소 침투를 관찰하였다. Self-etching primer를 도포한 군과 도포하지 않은 군 사이에는 평균 미세누출량에 유의한 차이가 없었다. 주사 바늘로 적용한 군과 paper point로 적용한 군 사이에도 평균 미세누출량에 유의한 차이가 없었다. 상아질과 근관 sealer계면의 주사전자현미경 관찰 결과 일부분에서 긴밀한 접착 관계를 나타내었고, 다른 부분에서는 간극을 나타내었다.

• Restorative Dentistry and Endodontics
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• v.25 no.4
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• pp.536-542
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• 2000

임상에서 점차 Mineral Trioxide Aggregate (MTA)에 대한 우수성이 소개되면서, apical matrix로의 사용은 주목할 만하다 할 수 있다. 본 연구의 목적은 개방형근관에서 MTA가 apical matrix로 사용될 때의 치근단 밀폐효과를 알아 보고, 근관충전의 시기와 matrix의 두께가 치근단 밀폐에 미치는 영향을 치근단 미세누출의 측면과 matrix탈락빈도의 측면에서 관찰하고자 하는 것이다. 개방형 근관을 재현하고자 45개의 발거된 단근치에 #90크기로 근단공을 형성하였고, 투명레진등을 이용하여 치근단 병소를 갖는 치조골을 재현한 후, 4개의 실험 군과 1개의 대조 군으로 분류하였다. A군: 2mm두께의 MTA matrix 형성후, 열연화된 Gutta-percha와 AH26 sealer를 이용하여 즉시 근관충전. B군: 2mm 두께의 MTA matrix 형성후, A군과 같은 방법으로 24시간 후 근관충전. C군: 4mm 두께의 MTA matrix 형성후, A군과 같은 방법으로 즉시 근관충전. D군: 4mm 두께의 MTA matrix 형성후, A군과 같은 방법으로 24시간 후 근관충전. 대조군: matrix를 사용하지 않고 열연화된 Gutta-percha와 AH26 sealer를 이용하여 근관충전하였다. Matrix의 탈락이 있는 경우 기록하고 완전 수세 후 다시 시행하였다. 색소침투정도의 평가를 위해 methylene blue에 치아를 48시간 침수시킨 후 협설로 양분하였다. 각 시편들을 고배율 현미경 관찰 후 비디오촬영 하였고, digitalized image analysing program을 이용하여 두명의 관찰자가 누출의 정도를 평가한 후, One-way ANOVA로 통계적 유의성을 검증하여 다음과 같은 결과를 얻었다. 1. Matrix를 사용한 실험 군이 matrix를 사용하지 않은 대조 군에 비해 유의성 있게 낮은 누출을 보였다(p<0.05). 그러나 근관충전시기와 matrix의 두께를 달리한 실험군 내에서는 누출에 유의성 있는 차이가 나타나지 않았다. 2. 모든 실험군에서 gutta-percha를 이용한 근관충전의 시기에 matrix탈락 및 gutta-percha의 압출은 발생하지 않았다.

• Restorative Dentistry and Endodontics
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• v.27 no.5
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• pp.479-487
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• 2002

복합레진의 중합시 발생하는 수축과 응력은 와동의 형태에 의하여 영향을 받으며 이는 수복재는 물론 접착계면의 물성을 결정하는 요인이 된다. 본 연구는 다양한 C-factor를 갖는 와동에 상아질 접착제 Clearfil SE Bond(Kuraray)를 도포하고 혼합형 복합레진인 Clearfil AP-X(Kuraray)와 미세혼합형의 Esthet-X(Dentsply)를 충전하여 미세인장강도 및 변연누출을 측정 평가함으로써 중합수축이 수복물과 치아계면에 미치는 영향을 평가하고자 시행하였다. 98개의 Bovine 하악전치를 이용하여 표면의 상아질을 #600 SiC paper로 연마한 대조군 및 와동의 넓이를 조절하여 C-factor 2.3, 3.0, 3.7이 되도록 제작한 실험군 와동에 복합레진을 충전한 후 37의 증류수에 24시간 보관하였다. 저속 diamond saw(Buehler)를 이용하여 1mm 두께로 수직절단 후 고속 diamond point(#104 Shofu)를 이용하여 단면적 1mm$^2$가 되도록 hour-glass모양으로 형성하여 시편을 제작하였고, Universal testing machine(EZ-Test; Shimadzu, Japan)에 시편을 부착하고 cross head speed 1mm/min으로 인장력을 가하여 미세인장 결합강도를 측정하였다. 각 C-factor에 따른 변연누출실험을 위하여 복합레진이 수복된 치아를 37$^{\circ}C$의 증류수에 24시간 보관한 후 와동을 제외한 부위에 nail varnish를 도포하고 3mol/L silver nitrate용액에 24시간 암보관한 다음 수세하여 현상액에 24시간 경과시킨 후 치아의 장축에 따라 절단하여 침투된 색소의 정도를 광학현미경상에서 40배로 관찰하였다. 각각의 실험결과는 ANOVA/Tukey's test 및 Kruskal-Wallis non-parametric independent analysis와 Mann-Whitney U test에 의하여 통계 분석하여 다음과 같은 결론을 얻었다. 1. 대조군에 있어서 혼합형 복합레진의 미세인장 결합강도는 미세혼합형에 비하여 높았으며, 실험군 사이에는 유의차를 보이지 않았다. 2.모든 복합레진의 미세인장 결합강도는 와동의 C-factor증가에 따라 감소하는 경향을 나타내었고, 혼합형 복합레진의 실험군은 대조군에 비하여 낮게 나타났으며, 미세혼합형 복합레진에서는 유의차를 보이지 않았다. 3. 절단측 및 치은측 변연부의 미세누출정도는 혼합형 복합레진이 미세혼합형에 비하여 대체로 높게 나타났다. 4. 모든 실험군에서 미세누출은 C-factor증가에 따라 증가하였고 절단측에 비하여 치은측 변연이 높게 나타났으나 통계학적 유의차는 보이지 않았다. C-factor의 변화에 대하여 필러함량과 탄성계수가 높은 혼합형 복합레진이 미세혼합형에 비하여 더 민감한 결과를 보인다. 이는 복합레진 수복시 재료의 선택과 중합수축의 적절한 조절이 중요한 요소임을 시사한다.

• Korean Journal of Environmental Biology
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• v.17 no.1
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• pp.1-9
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• 1999

Numerous observations revealed strong evidence of increased middle ultraviolet radiation or UV-B (280 ~ 320 nm) at the earth's surface resulting from stratospheric ozone depletion. UV is the waveband of electromagnetic radiation which is strongly absorbed by nucleic acids and proteins, thus causing damage to living systems. It has been recorded in the East Sea, Korea that solar UV-B impinging on the ocean surface penetrates seawater to significant depths. Recent researches showed that exposure to UV-B for as short as 2h at the ambient level (2.0 Wm$^{-2}$) decreased macroalgal growth and photosynthesis and destroyed photosynthetic pigments. These may suggest that UV-B could be an important environmental factor to determine algal survival and distribution. Some adaptive mechanisms to protect macroalgae from UV-damage have been found, which include photoreactivation and formation of UV-absorbing pigments. Post-illumination of visible light mitigated UV-induced damage in laminarian young sporophytes with blue the most effective waveband. The existence of UV-B absorbing pigments has been recognized in the green alga, Ulva pertusa and the red alga, Pachymeniopsis sp., which is likely to exert protective function for photosynthetic pigments inside the thalli from UV-damage. Further studies are however needed to confirm that these mechanisms are of general occurrence in seaweeds. Macroalgae together with phytoplankton are the primary producers to incorporate about 100 Gt of carbons per year, and provide half of the total biomass on the earth. UV-driven reduction in macroalgal biomass, if any, would therefore cause deleterious effects on marine ecosystem. The ultimate impacts of increasing UV-B flux due to ozone destruction are still unknown, but the impression from UV studies made so far seems to highlight the importance of setting up long-term monitoring system for us to be able to predict and detect the onset of large -scale deterioration in aquatic ecosystem.

• Proceedings of the KACD Conference
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• 2008.05a
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• pp.204-212
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• 2008

The purpose of this study was to compare the apical microleakage in root canal filled with Resilon by methacrylate-based root canal sealer or 2 different self-adhesive resin cements. Seventy single-rooted extracted human teeth were sectioned at the CEJ perpendicular to the long axis of the roots with diamond disk. Canal preparation was performed with crown-down technique using Profile NiTi rotary instruments and GG drill. Each canal was prepared to ISO size 40, .04 taper and 1 mm short from the apex. The prepared roots were randomly divided into 4 experimental groups of 15 roots each and 5 roots each for positive and negative control group. The root canals were filled by lateral condensation as follows. Group 1: Gutta-percha with AH-26, Group 2: Resilon with RealSeal primer & sealer, Group 3: Resilon with Rely-X Unicem, Group 4: Resilon with BisCem. After stored in $37^{\circ}C$, 100% humidity chamber for 7 days, the roots were coated with 2 layers of nail varnish except apical 3 mm. The roots were then immersed in 1% methylene blue dye for 7 days. Apical microleakage was measured by a maximum length of linear dye penetration after roots were separated longitudinally. One way ANOVA and Scheffe's post-hoc test were performed for statistical analysis. Group 1 showed the least apical leakage and there was no statistical significance between Group 2, 3, 4. According to the results, the self adhesive resin cement is possible to use as sealer instead of primer & sealant when root canal filled by Resilon.