Influence of Tricalcium Aluminate Phase on In Vitro Biocompatibility and Bioactivity of Calcium Aluminate Bone Cement
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S.Y. Choi Department of Ceramic Engineering, Yonsei University, Seoul 120-749, Korea
K.N. Kim Department of Biomaterials and Bioengineering, Yonsei University, Seoul 120-752, Korea (Received 17 September 2003; accepted 12 December 2003)
The influence of tricalcium aluminate (3CaO·Al2O3) phase doping on in vitro biocompatibility and bioactivity of calcium aluminate (CaO·Al2O3) based bone cement has been investigated. It is demonstrated that the presence of approximately 25% tricalcium aluminate in the bone cement remarkably improves the bioactivity, yet still retains desirable mechanical strength and biocompatibility. An intermediary compound layer such as Ca3Al2(OH)12 was formed on the surface of the doped sample onto which hydroxyapatite (HAp) began to form soon, after only 2 days of immersion in a simulated body fluid solution. This is about seven-fold acceleration in the HAp formation over undoped calcium aluminate cement on which it took approximately 15 days to nucleate the HAp phase. The depth of the HAp-containing layer after 60 days of soaking was as much as 85 m, about an order of magnitude more than the undoped calcium aluminate cement. The dramatically accelerated nucleation and growth of hydroxyapatite caused by the presence of tricalcium aluminate is attributed to the occurrence of intermediate layer materials such as Ca3Al2(OH)12, which most likely acts as the nuclei for HAp formation. This doped bone cement can be useful for injectable orthopedic applications, as the setting time for hardening has also been significantly reduced (by a factor of at least 4) to a practical regime of tens of minutes.
I. INTRODUCTION
Bioactive materials intended for accelerated bone growth/adhesion actions need to be biocompatible and have to be integrated by the surrounding bone tissue. It is generally acknowledged that these features apply to calcium phosphate based ceramics like HAp and tricalcium phosphate due to their chemical similarity to bone minerals. Some of the most important characteristics of the bioactive materials include excellent biocompatibility and a rapid formation of hydroxyapatite (HAp) layers on their surfaces. As the nucleation and growth of HAp crystallites originates from the reaction of calcium and a)
Address all correspondence to this author. e-mail: [email protected]. This author was an editor of this journal during the review and decision stage. For the JMR policy on review and publication of manuscripts authored by editors, please refer to http:// www.mrs.org/publications/jmr/policy.html. DOI: 10.1557/JMR.2004.0139 1062
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J. Mater. Res., Vol. 19, No. 4, Apr 2004 Downloaded: 14 Mar 2015
phosphate ions from the surrounding fluid,1 appropriate engineering of the availability of Ca or P element in orthopedic bioimplant materials could lead to optimization of bone generation. To date, much research has been devoted to the design of bioactive bone cement, which is mainly composed of Ca and P, as these elements constitute the main components of natural bone. Tricalc
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