1992 Fiscal Year Final Research Report Summary
Hardening and reaction mechanism of bioactive cement based on glass
| Project/Area Number |
03455015
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
広領域
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
KOKUBO Tadashi Kyoto University, Faculty of Engineering, Professor, 工学部, 教授 (30027049)
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| Co-Investigator(Kenkyū-buntansha) |
NAKAMURA Takashi Kyoto University, Research Center for Biomedical Engineering, Associate Professo, 生体医療工学研究センター, 助教授 (10201675)
OHTSUKI Chikara Kyoto University, Faculty of Engineering, Instructor, 工学部, 助手 (00243048)
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| Project Period (FY) |
1991 – 1992
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| Keywords | Bioactivity / Cement / Glass / Setting / Hardening |
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| Research Abstract |
The present authors recently found that a Cao,SiO_2-based glass powder sets in a few minutes, when mixed with an ammonium phosphate solution, and bonds to living bone when implanted into bone defect. Such type of bioactive cement is useful for bone filler, drug carriers in the drug delivery system etc. In the present study, setting and hardening mechanism of the bioactive glass cement and its reaction mechanism with a body fluid were investigated.
The compressive strength of the cement largely varied with small changes in the CaO/SiO_2/P_2O_5 ratios. Addition of the CaF_2 to CaO-SiO_2-P_2O_5 composition increased the compressive strength, whereas that of the MgO decreased it. The composition of CaO 47.1, SiO_2 35.8, P_2O_5 17.1, CaF_2 0.75 wt ratio gave the highest compressive strength among the examined compositions. Its compressive strength decreases when average particle size of the glass powders was above 5 mum. The compressive strength of the cement increased with increasing the concentration of ammonium phosphate in the solution. The solution of 3.7M ammonium phosphate at pH 7.0-8.3 gave the highest compressive strength. The setting of the cement is attributed to the formation of amorphous calcium phosphate(ACP) at the intergranular spaces of the glass powders. The ACP is formed by the reaction of P(V) ion in the ammonium phosphate solution with Ca(II) and Si(IV) ions dissolved from the glass. The hardening of the cement is attributed to the formation of the hydroxyapatite in place of ACP and to its growth and recrystallization. Once the Ca(II) and P(V) ions are fixed in the cement as calcium ammonium phosphate monohydrate before soaking into the simulated body fluid, it converts to a larger amounts of hydroxyapatite, and gives a higher compressive strength.
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