• Journal of the Korean Ceramic Society
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• v.52 no.5
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• pp.374-379
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• 2015

Mullite-matrix and $Al_2O_3$-matrix composites were fabricated with 30 wt% hydroxyapatite (HA) and tricalcium phosphate (TCP), respectively, as additives to give bioactivity. A diphasic gel process was employed to lower the densification temperature of the mullite matrix to $1320^{\circ}C$. A polymer complexation process was used to synthesize a TCP powder that was fully densified at $1250^{\circ}C$, for application to the matrix. For the HA/mullite composite, HA decomposed during sintering by reactions with the matrix components of $Al_2O_3$ and $SiO_2$, resulting in a mixture of $Al_2O_3$, TCP, and other minor phases with a low densification of less than 88% of the theoretical density (TD). In contrast, the TCP/$Al_2O_3$ composite was highly densified by sintering at $1350^{\circ}C$ to 96%TD with no reaction between the components. Different from the TCP monolith, the TCP/$Al_2O_3$ composite also showed a fine microstructure and intergranular fracture, both of which characteristics are advantageous for strength and fracture toughness.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.2
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• pp.79-85
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• 2005

Commercial hydroxyapatite (HA) powders were calcined at the temperature range of $1000{\sim}1350^{\circ}C$ in air, for 2h, and the calcined powders were immersed in simulated body fluid (SBF) of pH 7.4 at $37^{\circ}C$ for 3 or 7 days. Thermal decomposition and their related dissolution behaviors of hydroxyapatite were investigated by XRD, FT-IR, and TEM. At the temperature of $1200^{\circ}C$, HA gradually releases its $OH^-$ ions and transforms to OHAP((oxyhydroxyapatite, ($Ca_{10}(PO_4)_6O_x(OH)_{2-2x}$)). HA thermally decomposes to ${\alpha}-TCP$ (${\alpha}-tricalcium$ phosphate) and TTCP (tetracalcium phosphate) phase at $1350^{\circ}C$. It was found that the surface dissolution of the hydroxyapatite powders was accelerated by non-stoichiometric composition and decomposed to ${\alpha}-TCP$ and TTCP.

• The Korean Journal of Health Service Management
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• v.13 no.4
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• pp.133-144
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• 2019

Objectives: To analyze the radiologic results of patients treated with bone defects treated with beta-tricalcium phostphate (β-TCP) in orthopedic surgery. Methods: Medical records of 49 patients, consisting of 24 (49.0%) men and 25 (51.0%) women were retrospectively reviewed. Graft incorporation was evaluated based on Irwin's radiologic staging. Results: The explanatory power of the total regression equation in Irwin's stage at 3 months postoperatively according to three explanatory variables, namely graft tightness, age at diagnosis, and lesion volume, was 65.6%; the explanatory power of Irwin's stage at 6 months postoperatively according to two variables, namely lesion volume and graft tightness, was 32.9%; and the explanatory power of Irwin's stage at 9 months postoperatively for two variables, namely longitudinal lesion length and graft tightness in the total regression, was 30.8%. Conclusions: Graft tightness, lesion volume, age at diagnosis, and longitudinal lesion length are the common factors affecting graft incorporation.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.2
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• pp.171-176
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• 2000

The phosphatic calcium compounds such as calcium hydrogen phosphate, bone ash, hydroxyapatite and tricalcium phosphate were prepared using the high purity calcium hydroxide and calcium carbonate obtained from shell resources. Calcium hydrogen phosphate had been prepared using the high purity calcium hydroxide and phosphoric acid solution. Using the calcium hydrogen phosphate as a starting materials, bone ash have been prepared by solid state reaction method and hydroxyapatite could be obtained by hydrothermal treatment method, respectively. The tricalcium phosphate was prepared by the solid state reaction of a stoichiometic mixture of bone ash and high purity calcium carbonate. In this paper, the optimal preparation process and conditions of phosphatic calcium compounds were established.

• Journal of Ceramic Processing Research
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• v.20 no.6
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• pp.655-659
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• 2019

Calcium phosphates such as HA (hydroxyapatite), β-TCP (tricalcium phosphate) and biphasic HA/β-TCP, were synthesized by wet chemical precipitation in aqueous solution combined with ball milling process. Nanosize powders of the calcium phosphates were synthesized using Ca(OH)2 and H3PO4. The effects of initial precursor Ca/P ratio (1.30, 1.50 and 1.67), ball milling process and post heat-treatment on the phase evolution behavior of the powders were investigated. The phase of resulting powder was controllable by adjusting the initial Ca/P ratio. HA was the only phase for as-prepared powders in both cases of Ca/P ratios of 1.50 and 1.67. The single HA phase without any noticeable second phase was obtained for the initial Ca/P ratio of 1.67 in the overall heat-treatment range. Pure β-TCP and biphasic calcium phosphate (HA/β-TCP) were synthesized from precursor solutions having Ca/P molar ratios of 1.30 and 1.50, respectively, after having been heat-treated above 700 ℃. The β-TCP phase has appeared on the pre-existing DCPD (dicalcium phosphate dihydrate) and/or HA phase. Dense ceramics having translucency were obtained at a considerably lower sintering temperature. The modified process offered a fast, convenient and economical route for the synthesis of calcium phosphates.

• Cement Symposium
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• no.31
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• pp.87-91
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• 2004

• 대한치주과학회:학술대회논문집
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• 1998.11a
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• pp.41-42
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• 1998

• The Journal of the Korean dental association
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• v.27 no.2 s.237
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• pp.155-159
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• 1989

• Korean Journal of Poultry Science
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• v.15 no.3
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• pp.219-227
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• 1988

This experiment was carried out to evaluate biological availability of Ca and P in 4 different sources of tricalcium phosphate in young chicks. One hundred and twenty five-day-old male Single Comb White Leghorn chicks (10 treatments$\times$3replication$\times$4chicks) were used in trial 1 and 2, respectively, for 12 days of feeding period. Trial I was to evaluate the availability of phosphorus in the supplements, Standard purified diets were prepared to supply 0.07, 0.14 and 0.21％P using a mixture (1 : 1) of NaH$_2$PO$_4$ and KH$_2$PO$_4$ as the reference Phosphorus sources. Bone breaking strength of the tibia determeined by an Instron instrument appeared inadequate to be used as a criterion due to very high variations of the measurement within a treatment. Thus, tibia bone ash content was utilized as a criterion to evaluate th biological avilability of phosphorus in the supplements. The levels of the biological availability of the four different sources of dicalcium phoshate were 77.1, 91.0, 96.4 and 95.5％, respectively, and those of the three tricalcium phosphate sources were 94.1, 95.0 and 99.5％ , respectively. Trial 2 was to determeine the levels of Ca biologically available in the supplements. Standard purified diets were made to supply 0.2, 0.3 and 0.4％ Ca using CaCo$_3$ as the reference calcium source. When bone ash content was utilized as a criterion for the availability, the levels of calcium biologically available to the chicks were 78.3, 234.1, 87.6 and 244.5％, respectively, for the 4 different sources of dicalcium phosphate and 99.5, 84.0 and 101.5％ , respectively, for the 3 different sources of tricalcium phosphate. The observation that two calcium sources appeared to be utilized with an unusual efficiency can hardly be explained at this moment. When they were revaluated on the basis of body weight gain, the availabilities of the four sources of dicalcium phosphate were 89.2, 58.2, 104.1 and 103.1％ and of the three tricalcium phosphate were 112.6, 106.0 and 96.3％ , respectively.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.33 no.4
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• pp.308-313
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• 2011

Purpose: Beta-tricalcium phosphate (${\beta}$-TCP) is a synthetic calcium phosphate ceramic that has widely been used as a bone material to repair bone defects. Despite many clinical studies, the molecular mechanism whereby this biomaterial alters the gene expression in osteoblasts to promote bone formation is poorly understood. Thus, we attempted to address this question by using microarray techniques to identify the genes that are differentially regulated in osteoblasts exposed to ${\beta}$-TCP. Methods: By using DNA microarrays, we identified several genes whose expression levels were significantly up- or down-regulated in osteoblast-likeMG-63cells cultured with ${\beta}$-TCP at a concentration of 100 mg/10 ml for 24 hours. Results: The differentially expressed genes covered a broad range of functional activities: signal transduction, transcription, cell cycle regulation, vesicular transport, apoptosis, immunity, cytoskeletal elements and cell proliferation and differentiation. Conclusion: The gene expression changes related to cell proliferation and differentiation, vesicle transport, immunity and defense could affect the osteogenic activities of osteoblasts for bone regeneration. However, further studies will be required to verify the relative importance of these genes in bone formation, their temporal and spatial expression patterns and their interactions with each other.