The Study On The Preparation And Properties Of Calcium Silicate-Phosphate Composite Bone Cements

Calcium phosphate cement(CPC)is one of new type of artificial bone substitute materials.CPC are composed of powders and liguid.After mixing the cement powders with liquid,it will self-set at room temperature and form needle-shaped hydroxyapatite(HA)which chemical component and structure are similar to the mineral phase of hard tissue.CPC is attractive in a broad range of clinical application for repairing bone defects by the virtue of high biocompatibility and self-setting capability.However,CPC are restricted in clinical practice for its low strength.So it's an important researching topic for many researchers that how to enhance the strength of the calcium phosphate cement.In this thesis,needle-shaped wollatonite powders were synthesized by melt-crystallization route using calcium oxide and silicon dioxide as raw materials. Comminution methods of the wollastonite powders were researched.Tetracalcium phosphate (TTCP),α-tricalcium phosphate(α-TCP),dicalcium phosphate dihydrate(DCPD),calcium carbonate(CaCO₃),hydroxyapatite(HA)and calcium pyrophosphate(CPP)were chosen as compositions of phosphate bone cement(CPC)and the Ca/P ration of the bone cement were decided as 1.50.The different amount of needle-shaped wollastonite synthesized by melting-crystallization route was added in the basic bone cements and the primary properties of them were studied.The crystallization conditions,crystalline phases and microstructure of wollastonite powders had been studied by means of DTA,XRD,SEM and optical microscope.The effects on the length-diameter ratio of the different equipments for preparation of needle-shaped wollastonite powders were discussed.The results show that the main crystalline phase of synthesized wollastonite isβ-CaSiO₃.Compared with different crush methods,the product by jet mill has remarkable excellent needle-shaped structure and larger-length diameter ratio, medium agitating mill can destroy the needle crystal structure of wollastonite.The initial setting time(It)and the final setting time(Ft)of bone cements were tested by Gilmore double-needle method.The changes of pH value in Ringer's solution were determined by PHS-25 acidometer.The compressive strength of the samples was tested by a microcomputer controlled poly-function tester.The phase transition and microstructure of bone cements is studied by X-ray diffraction instrument and scanning electron microscope respectively.The results show that the needle-shaped wollastonite can accelerate the setting of the CPC and increase the compressive strength.The properties of bone cement reach the best when the addition amount of needle-shaped wollastonite is 3%.The initial setting time is 14min and the final setting time is 28min.The compressive strength of bone cement reaches 49.23Mpa.The pH value of solution changed in the region of 7.3～7.8 which was close to neutrality.The results of XRD and SEM show that the prorer quantity of needle-shaped wollastonite can accelerat the formation of HA,and the structure of bone cement is more impact,consequently the strength of bone cement can be increased.