Research On Evolution During Hydration Process And The Composite Of CPC

Calcium Phosphate Cement (CPC) is widely used as bone substitutes in dentistry, orthopedics and reconstructive surgery, because of its biocompatibility, osteoconductivity and biodegradability. However, the high brittleness, low strength and slow biodegradation restrict its clinical application. And implant-caused infections are considered to be very serious too. As a result, it is very important to improve the mechanical strength of CPC as well as to make it antibacterial. In addition, there are few reports on the changes of CPC during hydration process from liquid to solid, which influence the improvement of CPC.So in this experiment, two kinds of CPC powders, aH-TCP and TTCP/DCPA, were prepared first and studied the changes of them during hydration process from liquid to solid by X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and especially high temperature X-ray diffraction. Then, The composites CPC/PLA/Cefazolin were prepared to make CPC high strength and antibacterial at the same time. The strength, microstructure, the properties of degradation and releasing antibiotics and so on were studied whereafter.The results of different tests showed consistency. The changes of aH-TCP and TTCP/DCPA bone cements were similar during hydration process, and the hydration process could be divided into three periods. The reactant dissolved gradually and the last product was the same HA; The microstructure was granular first, then was filmy, and granular protrudently, and claviform or acicle further, a close-grained corrugated structure was existent at the same time; The hydrate heat evolution curve of CPC was similar with cement. The reaction could be divided into five periods with different mechanisms. The results tested by high temperature X-ray diffraction was accordant with the changes of CPC during hydration process from liquid to solid. In earlier period, the cluster was noncrystal and very disordered. Liquid structure changed steadily without shape change of cluster. The crystal nucleus formed steadily, and the cluster was ordered gradually with the crystallization of HA. The strength of CPC added Cefazolin could be decreased because of the increase of pores; however, adding PLA could cause the close-grained structure, so the strength of CPC increased. Moreover, macropore created by PLA hydrolysing could accelerate the degradation of CPC and the ingrowth of new bone tissue. The composites with Cefazolin could release antibiotics slowly. In the earlier period, the speed of release was faster. About 5 days later, Cefazolin was released steadily. The earlier released speed and the total amount of Cefazolin released increased with the increase of Cefazolin contents. The addition of PLA had influence on the release of Cefazolin and had contribution to the long-term release after 50 days.