[Effects of collagen on the properties of TTCP/MCPM bone cement]

Bone cement samples were made of tetracalcium phosphate (TTCP) and monocalcium phosphate monohydrate(MCPM) powder (Ca/P = 1.67) by using water and 5.24 mg/ml of self-made type I collagen sol as hardening liquid with the solid-liquid ratio of 3:1, their setting time and compressive strength were tested. The results showed that: the compressive strength of TTCP/MCPM bone cement containing collagen could increase from 17.8 +/- 1.9 MPa to 22.7 +/- 1.6 MPa, but its setting time hasn't been significantly affected; the compressive strength of both samples immersed in simulated body fluid (SBF) could increase, and the growth rate of the sample containing collagen increased especially; both samples immersed in SBF for 4d and 14d, whose compressive strength could increase to 31.8 +/- 3.9 MPa (collagen)/19.5 +/- 1.3 MPa and 38.1 +/- 3.1 MPa (collagen)/21.9 +/- 2.2 MPa. According to the IR analysis before and after the collagen was mineralized, it showed that: after the collagen was mineralized, the characteristic peaks of the collagen's amide I band showed red-shift, while the amide II band and the amide III band nearly disappeared, suggesting that chemical action occurred between the collagen and hydroxyapatite (HA), which should be the basis of the enhancement on the TTCP/MCPM bone cement caused by collagen; while according to the SEM and XRD patterns of the sample surface before and after the samples were immersed in SBF, it showed that: the immersion in SBF changed brushite (DCPD) into HA, at the same time, large number of new HA deposited, making the samples' surface more dense and smooth. It was not only the enhancement mechanism of immersion in SBF, but also showed the coagulating and hardening process of TTCP/MCPM bone cement was that: the DCPD was generated firstly, then it changed into HA.