• Restorative Dentistry and Endodontics
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• 제10권1호
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• pp.71-83
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• 1984

The purpose of this study was to evaluate the transmission spectrum of the set calcium hydroxide dental cement (Dycal, L.D. Caulk Co. Milford, Del.) Cement was prepared for A T R spectra at a low powder-to-liquid ratio of 3.0gm/ml in order to retard the reaction and facilitate the manipulation of loading the cement into the cell. Spectra were recorded on an I R Spectrophotometer (MX-1, FT) at an agle of incidence of 55. The A T R cell was a RIIc Model TR5 with a hemisperical KRS-5 (Thallium-Bromide-Iodide). A spectrum was recorded within 3 minutes. Further spectra were recorded after 5,10,30 minutes and 1,5,24, 72 hours. The results were as follows; 1. The setting reaction between acid paste and base past would take place fastly within 10 minutes after mix, and that would be slow until 72 hours after mix. 2. In the set cements, some methyl salicylate and calcium hydroxide remained unreacted until 72 hours after mix. 3. The setting reaction and the reaction rate occuring at the surface and in the bulk cements were similar. 4. The chelates were bound together between calcium hydroxide and methyl salicylate.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2021년도 가을 학술논문 발표대회
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• pp.176-177
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• 2021

In order to compensate for the defects of concrete made using only Portland cement, three-component powder mixed with blast slag and fly ash, and four-component powder concrete mixed with silica fume are being produced. When each of the admixtures is used alone, the above-described excellent performance is expressed and up to 70% of the powder is used. These technologies are also contributing to the reduction of greenhouse gases under Act on Low Carbon. Green Growth. However, calcium hydroxide is consumed as a stimulator or reaction in the case of silica fume, which causes latent hydroponicity of slag, pozzolane reaction, and silica mixtures represented by fly ash. It is known that the consumption of calcium hydroxide affects the alkalinity of concrete. As a result, the carbonation resistance is significantly lower among the durability of concrete. Research on quantification of such effects is insufficient. In this study, an experiment was conducted to quantify calcium hydroxide of the three-component and four-component powder paste using thermal analysis equipment (DTG), and the effect of the mixing amount was discussed.

• 한국지반공학회논문집
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• 제28권3호
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• pp.67-75
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• 2012

본 연구에서는 식물추출액을 이용하여 모래 입자 사이에 친환경적으로 탄산칼슘을 석출시켜 모래 고결을 유발하고자 하였다. 식물추출액에는 고결유발 미생물(예: $Sporosarcina$ $pasteurii$)과 같이 요소를 탄산이온과 암모늄이온으로 분해하는 우레아제 성분이 포함되어 있다. 분해된 탄산이온과 용액 속에 녹아 있는 칼슘이온이 결합하여 탄산칼슘을 석출시키는 원리를 이용하여 모래의 고결을 유도하였다. 깨끗한 낙동강모래에 식물추출액과 요소 그리고 칼슘원(염화칼슘 또는 수산화칼슘)을 혼합한 용액을 섞어서 비빈 다음 다짐방법으로 공시체를 제작하였다. 요소의 농도를 세 종류로 달리하였으며, 제작된 공시체를 실내($18^{\circ}C$)에서 3일 동안 양생시킨 다음 일축압축시험과 SEM 및 XRD분석을 실시하여 사질토의 고결 정도를 연구하였다. 칼슘원에 관계없이 요소의 농도가 높을수록 탄산칼슘이 더 많이 침전되어 일축압축강도는 식물추출액을 사용하지 않은 경우보다 최대 10배까지 증가하는 경향을 보였다. 염화칼슘을 사용한 공시체가 수산화칼슘을 사용한 경우보다 더 높은 강도를 나타내었다.

• Restorative Dentistry and Endodontics
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• 제10권1호
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• pp.31-42
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• 1984

The toxic effect of adhesive resins on the dog's pulp tissue was studied with 70 teeth from 5 dogs. The experimental materials were Clearfil, a mixture of Clearfil with calcium hydroxide powder, Panavia-EX, and a mixture of Panavia-EX with calcium hydroxide powder. As a control group, calcium hydroxide powder was used. Each material was placed on the pulpotomized tissue surface. After 3 days, 1, 2,4, and 6 weeks, the teeth and apical tissue were processed routinly and stained with hematoxylin and eosin. Pathological tissue changes due to the toxicity of adhesive resins were observed by light microscope, and the pH of Panavia-EX and the Bonding agent of Clearfil were measured. Following were the results; 1. In the group of calcium hydroxide powder, slight inflammatory change was observed in the pulpotomized surface and adjacent pulp tissue on 3 day. 1 week case showed incomplete dentin bridge. The remaining pulp tissue was normalized according to the days elapsed. 2. In the group of Clearfil, early inflammatory change revealed in the superificial portion of the remaining pulp tissue on 3 day. The inflammation spreaded over the total pulp tissue and partial necrosis was observed in 1 week and 2 week cases. Total necrosis of pulp tissue and moderate inflammatory change at the apical tissue was noticed in 4 week and 6 week cases. 3. In the group of Panavia-EX, moderate inflammatory change appeared in the superficial pulp tissue on 3 day, and severe inflammatory change over all pulp tissue found in 1 week case. Pulp necrosis was obvious in 2 week case. 4 week and 6 week cases were totally necrotized up to the periapical tissue. 4. In the groups of mixtures with calcium hydroxide powder, the pulp tissue destruction was retarded, compared with the groups of Clearfil and Panavia-EX. 5. Panavia-EX was more destructive than Clearfil. 6. The acidity of freshly mixed Bonding agent of Cleafil was pH 4.0, and that of Panavia-EX was pH 2.0.

• 공학논문집
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• 제5권1호
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• pp.73-87
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• 2004

수산화칼슘현탁액과 탄산가스를 출발물질로 15~$50^{\circ}C$의 온도에서 기액반응으로 비정질 탄산칼슘($CaCO_3$.$nH_2 O$)의 생성과정을 전기저도도의 연속측정법, X-선회절법 및 투과전자현미경법을 이용하여 조사한 결과, 반응초기생성물은 비정질 탄산칼슘으로 반응현탁액의 전기전도도는 비정질 탄산칼슘의 생성 중 크게 강하하고 있으며, 이것은 수산화칼슘의 입자표면이 비정질 탄산칼슘미립자로 뒤덮여 용해를 방해받는 것과 비정질 탄산칼슘이 용액 속에서 불안정하여 즉시 용해한 다음 석출하여 칼사이트로 전이되어 미세한 침강성 탄산칼슘이 나란히 결합한 연쇄형 칼사이트가 생성된다. 비정질 탄산칼슘이 연쇄형 칼사이트로 변화하는 동안 현탁액의 전기전도도는 급격히 회복되고 이 과정에서 고농도 수산화칼슘현탁액의 외관점도가 상승한다. 이것은 연쇄형 칼사이트의 뒤얽힘에 의한 것이며, 다시 전기전도도의 1회 회복단계 이후에는 미반응 수산화칼슘에 의하여 비정질 탄산칼슘이 생성이 소멸되어 칼사이트의 성장반응이 이루어지고 pH가 9.5이하에서 연쇄형 칼사이트는 결합부분이 먼저 용해하여 결정질 탄산칼슘으로 분리생성된다. 비정질 탄산칼슘의 생성 및 합성온도의 영역은 전기전도도법에서 $15^{\circ}C$일 때 1차 강하단계(a-단계)에서 가장 적합하다.

• 한국분말재료학회지
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• 제23권3호
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• pp.221-227
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• 2016

Waste oyster shells create several serious problems; however, only some parts of them are being utilized currently. The ideal solution would be to convert the waste shells into a product that is both environmentally beneficial and economically viable. An experimental study is carried out to investigate the recycling possibilities for oyster shell waste. Bulk ceramic bodies are produced from the oyster shell powder in three sequential processes. First, the shell powder is calcined to form calcium oxide CaO, which is then slaked by a slaking reaction with water to produce calcium hydroxide $Ca(OH)_2$. Then, calcium hydroxide powder is formed by uniaxial pressing. Finally, the calcium hydroxide compact is reconverted to calcium carbonate via a carbonation reaction with carbon dioxide released from the shell powder bed during firing at $550^{\circ}C$. The bulk body obtained from waste oyster shells could be utilized as a marine structural porous material.

• Restorative Dentistry and Endodontics
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• 제38권4호
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• pp.227-233
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• 2013

Objectives: The purpose of the study was to evaluate human dental pulp response to pulpotomy with calcium hydroxide (CH), mineral trioxide aggregate (MTA), and calcium enriched mixture (CEM) cement. Materials and Methods: A total of nine erupted third molars were randomly assigned to each pulpotomy group. The same clinician performed full pulpotomies and coronal restorations. The patients were followed clinically for six months; the teeth were then extracted and prepared for histological assessments. The samples were blindly assessed by an independent observer for pulp vitality, pulp inflammation, and calcified bridge formation. Results: All patients were free of clinical signs/symptoms of pulpal/periradicular diseases during the follow up period. In CH group, one tooth had necrotic radicular pulp; other two teeth in this group had vital uninflamed pulps with complete dentinal bridge formation. In CEM cement and MTA groups all teeth had vital uninflamed radicular pulps. A complete dentinal bridge was formed beneath CEM cement and MTA in all roots. Odontoblast-like cells were present beneath CEM cement and MTA in all samples. Conclusions: This study revealed that CEM cement and MTA were reliable endodontic biomaterials in full pulpotomy treatment. In contrast, the human dental pulp response to CH might be unpredictable.

• 상하수도학회지
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• 제32권3호
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• pp.235-242
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• 2018

Corrosion inhibitors including calcium hydroxide have been used to prevent corrosion in the pipes for tap water supply. The corrosion index (i.e., Langelier Index) differs by area and water quality. The corrosion indices of the areas studied differed by more than 2.0. The 'homogenized' calcium hydroxide was added to the treated water at the K water treatment plant, in order to increase the value of the corrosion index and the concentration of calcium. As the result, the concentration of calcium was increased while the turbidity and pH changed little. The corrosion rate of the tap water with the 'homogenized' calcium hydroxide could be slowed down pretty much. The results suggested that the technology of 'homogenization' of calcium hydroxide can applied to tap water and desalinated water to prevent corrosion in water pipes even in corrosive pipes.

• 한국세라믹학회지
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• 제28권9호
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• pp.739-749
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• 1991

Calcium hydroxide fine powders were synthesized by hydration of calcium oxide, and the shapes of powders obtained were examined for each synthethic condition. When distilled water was used as a solvent, irregular and agglomerated submicron powders were obtained, and it was impossible to control of the shapes. In methanol-added solutions, hexagonal plate-like particles were obtained, but addition of ethanol had no effect. However on the occasion that substituted ethylene glycol for ethanol of 5 vol%, hexagonal plate-like powders were obtained. The shapes of powders synthesized in acetic acid and salicylic acid solutions were hexagonal platelike, and were spherical and very fine in citric acid and oxalic acid solutions, respectively. But in some solutions, calcium salts were precipitated by the reaction between calcium and acid added. And the size of powders were very fine using ultrasonic vibration instead of mechanical agitation.

• 대한치과보존학회:학술대회논문집
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• 대한치과보존학회 2001년도 추계학술대회(제116회) 및 13회 Workshop 제3회 한ㆍ일 치과보존학회 공동학술대회 초록집
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• pp.565.2-565
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• 2001

Calcium hydroxide is unavoidably left on the root canal wall when used as an intracanal medicament, and is assumed to have some undesirable influence on the canal sealers. The purpose of this study was to determine whether the $Ca(OH)_2$ change physical properties (Exp. I) and sealing ability (Exp. II) of root canal sealers. Exp. I: As calcium hydroxide agents, $Calcipex^{\circledR}, {\;}Vitapex^{\circledR}, {\;}Calxyl^{\circledR}, {\;}and{\;}Ca(OH)_2$ were used.(omitted)