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Biodegradable cement type bone implant materials based on calcium phosphates and calcium sulphate

Siek D., Czechowska J., Zima A., Ślósarczyk A.

Engineering of Biomaterials

2015

Vol. 18, no. 133

2--6

Calcium phosphates (CaPs) are widely used in hard tissue replacement because of their excellent biocompatibility. Calcium phosphate cements (CPCs) are an interesting alternative for sintered calcium phosphate ceramics due to their mouldability and self-setting properties which allow them to conform to even the most complex bone defects. However, one of the major limitations of CPCs is their relatively low resorption rate, not optimal for bone regeneration. The aim of our studies was to combine a stable hydroxyapatite with more soluble α-tricalcium phosphate (α-TCP) or calcium sulphate (CS) (resorbability: CS>>α-TCP>HA) to develop biomaterial with gradual degradation. Promising materials for use in minimally invasive surgery for bone defects repair were obtained. It was found that the degradation rate of hydroxyapatite based bone substitutes can be controlled by the addition of an appropriate kind and amount of more soluble constituent. The impact of the setting component (α-TCP or CS) on the physicochemical properties of the final products was confirmed. Furthermore the influence of organic additives (chitosan, methylcellulose, alginate) on the final materials characteristic was proven. Solutions of organic additives, applied as the liquid phases, significantly improved the workability of cement pastes. It has been demonstrated that implant materials based on calcium sulphate and α-TCP differed in their setting times, mechanical strength, dissolution rate and morphologies of apatite layers on their surfaces after soaking in simulated body fluid. The reason of observed differences is a higher susceptibility of calcium sulphate to both disintegration and degradation.

Chemically bonded, calcium phosphate based bioceramics with addition of calcium sulphate

Czechowska J., Siek D., Zima A., Ślósarczyk A.

Archives of Materials Science and Engineering

2014

Vol. 66, nr 1

5--12

Purpose: Calcium phosphate cements (CPCs) are extensively used as synthetic bone grafts due to their excellent bioactivity, moldability and ability to set in vivo. Although there are some commercial CPCs in the market, there are many ongoing research directed mainly to improve some of their properties, such as mechanical strength, cohesion or resorbability. The purpose of the study was to develop a more systematic approach for the formulations of CPCs and to obtain complex composite that will be gradually resorbed in vivo. Design/methodology/approach: In the present studies cements composed of different ratios of α-TCP, Mg2+/CO32- co-substituted hydroxyapatite (MgCHA) and calcium sulphate were developed. The obtained materials were characterized in terms of setting time, compressive strength and open porosity. XRD technique was employed to determine the phase composition of the initial powders and the final materials. Chemical stability of the studied materials was checked. Bioactive potential of the bone cements was evaluated in accordance to Kokubo’s protocol. Findings: The investigated materials possess excellent handling properties, appropriate setting times (initial: 6-8 min, final-17-21 min) and compressive strength comparable to cancellous bone (6-12 MPa). The expected gradual resorption of composites (resorbability: CSD >> α-TCP > MgCHA) is believed to facilitate a healing process and stimulate bone regeneration. Research limitations/implications: Further in vitro and in vivo experiments need to be done to confirm cytocompatibility of these biomaterials. Originality/value: The new chemically bonded bioceramics with addition of calcium sulphate was developed. A systematic approach for the formulations of CPCs on the basis of α-TCP, MgCHA and calcium sulphate was performed. The obtained chemically bonded bioceramics may have a chance to be apply as bone substitutes in low load bearing places.