• Journal of the Korean Ceramic Society
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• v.41 no.3
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• pp.259-265
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• 2004

The microstructure of nano-sized hydroxyapatite (HAp) powders coating layer on ZrO$_2$ substrate was investigated, which was formed by plasma spray process. The nano-sized HAp powders were successfully synthesized by precipitation of Ca(NO$_3$)$_2$$.$4H$_2$O and (NH$_4$)$_2$HPO$_4$ solution. The HAp coating layer with thickness of 150∼250 $\mu\textrm{m}$ was free from the cracks at interfaces between the coating and ZrO$_2$ substrate. In the plasma sprayed HAp coating layer, the undesirable phases were not found, while in the HAp coating layer heat-treated at 800$^{\circ}C$, TTCP, and ${\beta}$-TCP phase were detected as well as HAp phase. However, at 900$^{\circ}C$, they were completely disappeared. At 1100$^{\circ}C$, XRD analysis revealed that the coating layer was composed of the highly crystallized HAp.

• Journal of the Korean Ceramic Society
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• v.54 no.5
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• pp.395-399
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• 2017

The thermal properties and crystallization behavior of calcium phosphate glass fabricated using eggshell were examined. Nature eggshell has several impurities in the main component of $CaCO_3$. To manufacture calcium phosphate glass, washed eggshell was dissolved in aqua-regia while adding a solution of isopropyl alcohol, D. I. water and phosphoric acid. The calcined precursor was melted at $1000^{\circ}C$, and the glass ($T_g$ : $540^{\circ}C$) was crystallized at $620{\sim}640^{\circ}C$, which temperature range is relatively low compared to the crystallization temperature of other general types of calcium phosphate glass. The calcium phosphate glass using eggshell was successfully crystallized without any additional nucleating agents due to the multiple effects of impurities such as $Fe_2O_3$, $Al_2O_3$, SrO and $SiO_2$ in the eggshell. The main crystalline phase was ${\beta}-Ca(PO_3)_2$ and a biocompatible material, hydroxyapatite, was also observed. The crystallization process was completed under the condition of a holding time of only 1 h at the low temperature.

• Restorative Dentistry and Endodontics
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• v.37 no.1
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• pp.16-23
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• 2012

Objectives: Present study was undertaken to investigate the crystal growth onto synthetic hydroxyapatite (HA) seeds in pH 4.3 and pH 7.0 supersaturated solutions with different fluoride concentrations. Materials and Methods: 8 groups of pH 4.3 and 7.0 calcium phosphate supersaturated solutions were prepared with different fluoride concentrations (0, 1, 2 and 4 ppm). Calcium phosphate precipitates yield crystal growth onto the HA seed surface while solutions flow. For evaluation of crystallizing process, the changes of $Ca^{2+}$, $PO{_4}^{3-}$, $F^-$ concentrations of the inlet and outlet solutions were determined. The recovered solid samples were weighed to assess the amount of minerals precipitated, and finally determined their composition to deduce characteristics of crystals. Results: During the seeded crystal growth, there were significantly more consumption of $Ca^{2+}$, $PO{_4}^{3-}$, $F^-$ in pH 4.3 solutions than pH 7.0 (p < 0.05). As fluoride concentration increased in pH 4.3 solution, $Ca^{2+}$, $PO{_4}^{3-}$, $F^-$ consumption in experimental solutions, weight increment of HA seed, and fluoride ratio in crystallized samples were increased. There were significant differences among the groups (p < 0.05). But in pH 7.0 solution, these phenomena were not significant. In pH 7.0 solutions, analyses of crystallized samples showed higher Ca/P ratio in higher fluoride concentration. There were significant differences among the groups (p < 0.05). But in pH 4.3 solution, there were not significant differences in Ca/P ratio. Conclusions: Crystal growth in pH 4.3 solutions was superior to that in pH 7.0 solutions. In pH 4.3 solutions, crystal growth increased with showed in higher fluoride concentration up to 4 ppm.

• Environmental Engineering Research
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• v.10 no.5
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• pp.205-212
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• 2005

The study was conducted to investigate the removal of heavy metals by using Hydroxyapatite(HAp) made from waste oyster shells and wastewater with high concentration of phosphorus. The maximum calcium concentration for the production of HAp in this study was released up to 361 mg/L at pH of 3 by elution experiments. When the pH was at adjusted 6, the maximum calcium released concentration was 41 mg/L. During the elution experiment, most of the calcium was released within 60 minutes. This reaction occurred at both pH levels of 3 and 6. The result of the XRD analysis for the HAp product used in this study shows the main constituent was HAp, as well as OCP. The pH was 8.6. As the temperature increased, the main constituent did not vary, however its structure was crystallized. When the pH was maintained at 3, the removal efficiency decreased as the heavy metal concentration increased. The order of removal efficiency was as follows: $Fe^{2+}$(92%), $Pb^{2+}$(92%) > $Cu^{2+}$(20%) > $Cd^{2+}$(0%). Most of these products were dissolved and did not produce sludge in the course of heavy metals removal. As the heavy metal concentration increased at pH of 6, the removal efficiency increased. The removal efficiencies in all heavy metals were over 80%. From the analysis of the sludge after reaction with heavy metals, the HAp was detected and the OCP peak was not observed. Moreover, lead ion was observed at the peaks of lead-Apatite and lead oxidant. In the case of cadmium, copper and iron ions, hydroxide forms of each ion were also detected.

• Journal of the Korean Ceramic Society
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• v.48 no.1
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• pp.26-33
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• 2011

The glass in the system of CaO-$SiO_2-P_2O_5$ and the corresponding glass-ceramics are prepared for bone cements and the behaviors of the hardening and hydroxyapatite formation were studied for the glass and glass-ceramic powders. The glass crystallized into apatite, $\alpha$-wollastonite and $\beta$-wollastonite depending on the glass composition when they were heat-treated at $950^{\circ}C$ for 4 h. A DCPD (dicalcium phosphate dihydrate : $CaHPO_4{\cdot}2H_2O$) was developed when the prepared glass and glass-ceramic powders were mixed with 3M-$H_3PO_4$ solution. The DCPD (Ca/P=1.0) transformed to HAp (Ca/P=1.67) when the bone cement was soaked in simulated body fluid (SBF), and this HAp formation strongly depended on the releasing capacity of $Ca^{2+}$ ions from the glass and glass-ceramic cements. The glass-ceramic bone cement containing $\alpha$-wollastonite crystals showed faster transformation of DCPD to HAp than other glass-ceramics containing $\alpha$- and $\beta$-wollastonite crystals. No hydroxyapatite was observed when the glass-ceramic bone cement containing apatite crystals (36P6C) was soaked in SBF even for 1 month, because no $Ca^{2+}$ ion can be released from the stable apatite crystals.

• The Journal of Korean Academy of Prosthodontics
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• v.42 no.5
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• pp.556-571
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• 2004

Statement of problem: Surface texture of the implant is one of the important factors of the implant success, especially in the immediate implant loading. Many methods of the surface treatment of implant have developed and introduced. Purpose : This study was to evaluate the effects of the Ca-P coating implant crystallized the hydroxyapatite on the surface by the removal torque test and the histomorphometric analysis in vivo. Material and methods: 135 screw type implants, 4.0mm in length and 3.75mm in diameter were used in this study. Implants were divided into 3 groups and treated in the different mothods. Group I was not treated, Group II was treated in the SLA method, and Group III was treated in the Ca-P coating with the anodizing method and the hydroxyapatite was crystallized on the surface with the hydrothermal treatment. Firstly, the surface roughness of each group was measured, 45 rabbits were used in this experiment. Two implants were inserted on right tibial metaphysis and one implant was inserted on left side with the alternating order. After the healing periods of 3, 5, and 12 weeks, the rabbits were sacrificed to evaluate the osseointergration by the removal torque test and the histomorphometric analysis. Results : 1. In the analysis for the surface roughness, Group II showed the highest roughness. And Group III showed higher secondly. There was a significant difference one another statistically 2. In the removal torque test, Group III and II were significantly higher than Group I. There was no statistical difference between Group III and Group II. 3. For all Groups, the removal torque values at 12th week were significantly higher than at 3rd and 5th week. 4. In histomorphometric analysis, the bone implant contact rates of Group III and II were higher than that of Group I at 3rd and 5th week. There was a significant difference at 5th week. 5. In histomorphometric analysis, the bone implant contact rate of Group III and II increased from 3rd week to 5th week, but decreased at 12th week. In Group I, the contact rate at 12th week was significantly higher than at 3rd week and 5th week.

• Archives of Plastic Surgery
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• v.37 no.4
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• pp.340-345
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• 2010

Purpose: Recently, bioceramics have become popular as a substitute graft material for reconstruction of bony defect after trauma or tumor surgery. Among the bioceramic materials, hydroxyapatite (HA) is favored due to its biocompatibility. HA scaffold is composed of the interconnected reticular framework, macropores and micropores. Macropores play an important role in cell migration, nutrients supply and vascular ingrowth. On the other hand, a number of micropores less than $10{\mu}m$ form an irregular surface on HA scaffolds, which prevents the osteoblast from adhering and proliferating on the surface of HA scaffold. Methods: In this study, three different groups were designed for comparison. In the first group (group A), conventional method was used, in which HA pellet was applied without surface pretreatment. The second group (group B) was given a HA pellet that has been coated with crystalline HA solution prior to application. In the third group (group C), the same method was used as the second group, where the pretreated HA pellet was heated ($1250^{\circ}C$, 1 hour) before application. Osteoblast-like cells ($2{\times}10^4$/mL) were scattered onto every pellet, then they were incubated in 5% $CO_2$ incubator at $37^{\circ}C$ for twelve days. During the first three days, osteoblast cells were counted using the hemocytometer daily. ALP activity was measured on the 3, 6, 9 and 12 culture days using the spectrophotometer. Results: Under SEM, group A showed a surface with numerous micropores, and group B revealed more rough crystal surface. Group C revealed a fused crystal appearance and flattened smooth surface. In proliferation and ALP activity of osteoblast cells, group C showed better results compared to group B. Group A which lacks pretreatment of the surface showed less osteoblast proliferation and ALP activity than group C, but showed better results than group B. Conclusion: We found that crystallized HA with heat treatment method enhances the osteoblasts proliferation and differentiation on the surface of HA pellets.

• The Journal of Korean Academy of Prosthodontics
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• v.49 no.4
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• pp.333-340
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• 2011

Purpose: The aim of this study was to study the effect of hydroxyapatite (HA) coating crystallinity on the proliferation and differentiation of human osteosarcoma cells. Materials and methods: Surface roughness of the titanium disks increased by anodizing treatment and then HA was coated using ion beam-assisted deposition (IBAD). HA coating was crystallized by heat-treated at different temperature ($100^{\circ}C$, $300^{\circ}C$, $500^{\circ}C$, $800^{\circ}C$). According to the temperature, disks were divided into four groups (HA100, HA300, HA500, HA800). With the temperature, crystallinity of the HA coating was different. Anodized disks were used as control group. The physical properties of the disk surface were evaluated by surface roughness tests, XRD tests and SEM. The effect of the crystallinity of HA coating on HOS cells was studied in proliferation and differentiation. HOS cells were cultured on the disks and evaluated after 1, 3, 5, and 7 days. Growth and differentiation kinetics were subsequently investigated by evaluating cell proliferation and alkaline phosphatase activity. Results: Regardless of the heat-treated temperature, there is no difference on the surface roughness. Crystallinity of the HA was appeared in the groups of HA500, HA800. HOS cells proliferation, ALP activity were higher in HA500 and HA800 group than HA100 and HA300. Conclusion: Within the results of this limited study, heat treatment at $500^{\circ}C$ of HA coating produced by IBAD has shown greater effect on proliferation and differentiation of HOS cells. It is considered that further in vivo study will be necessary.

• Journal of Korean Society of Water and Wastewater
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• v.33 no.1
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• pp.9-16
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• 2019

The algal blooms in stagnant streams and lakes have caused many problems. Excessive algae leads to disturbance of ecosystem and overload of water treatment processes. Therefore, phosphorus(P), source of algal blooms, should be controlled. In this study, a filtration trench has been developed to convert dissolved phosphorus into hydroxyapatite(HAP) so that it could be crystallized on the surface of 'phosphorus removal granular material'; and residual particulate phosphorus could be removed by additional precipitation and filtration. The front and rear parts of filtration trench consisted of 'phosphorus removal granular material contact bed' and 'limestone filtration bed', respectively. As a result of the column test using phosphorus removal granular material and limestone serially, $PO_4-P$ was removed more than 90% when EBCT(empty bed contact time) of the contact bed was over 20 minutes; and T-P represented 60% of removal efficiency when total EBCT was over 1.5 hours. The results of column tests to figure out the sedimentation characteristics showed that more than 90% of particulate phosphorus could be removed within 24 hours. It was necessary to optimize the filtration part in order to increase removal efficiency of T-P additionally. Also, it was confirmed through the simulation of Visual MINTEQ that most of particulate phosphorus in the column tests is the form of HAP. Based on the results of the study, it could be suggested that the design parameters are over 0.5 hour of EBCT for phosphorus removal granular material contact bed and over 1.5 hours of EBCT for limestone filtration bed.