Statistical experimental design for studies of porosity and compressive strength in composite materials applied as biomaterials

Composites studied in this work are the associations of aluminosilicates and 13% of calcium phosphates. These composites present great interest. They are destined to be applied in biomedical field, particularly in orthopedic or jawbone surgery. Calcium phosphates are composed of HA ( hydroxyapatite) and TCP (tricalcic phosphate). The success of synthesised bony biomaterials depends on two determinant factors: the porosity ( which facilitate the cells deposition and the vascularisation) and the compressive strength ( which permits the support of body charge). In this way, a statistical experimental design was employed to quantify the influence of these two synthesis parameters. It concerns the effect of the K2O/SiO2 molecular ratio (X-1) and the effect of the calcium phosphate (HA/TCP) weight % (X-2). The K2O/SiO2 molecular ratio characterises the synthesis of the aluminosilicate. It varies between two limit levels: the stoichiometric ratio K2O/SiO2 = 0.54 corresponding to: X-1 = - 1 and the ratio K2O/ SiO2 = 0.80 corresponding to X-1 = 1. In bony biomaterials field, various calcium phosphates are commonly used as biomaterials. In our previous works, the influence of the commercial hydroxyapatite HA and tri-calcium phosphate TCP ( 13 wt%) addition was investigated. To study the effect of calcium phosphate composition, the weight percentage of mixing HA and TCP varied between two levels: the composite aluminosilicate with 13 wt% of HA ( X2 = - 1) and the composite aluminosilicate with 13 wt% of TCP (X-2 = 1). Eight samples were studied. The statistical experimental design predicted answer surfaces for compressive strength and percentage of porosity. After the validation of models, it was possible to determine composite which presents best compromise between percentage of porosity and compressive strength. This composite will be evaluated by "in-vitro" and "in-vivo" studies to investigate its potential for forthcoming applied as biomaterial.