Effect of precursor's solubility on the mechanical property of hydroxyapatite formed by dissolution-precipitation reaction of tricalcium phosphate.

The effect of the solubility of the precursors, alpha tricalcium phosphate (α-TCP) and beta tricalcium phosphate (β-TCP) on the mechanical strength of hydroxyapatite (HAp) bone substitute was investigated. Uniaxially pressed block starting from these precursors were treated hydrothermally with 1 mol/L of ammonia solution at 200°C for various durations. XRD analysis revealed that α-TCP block took 3 h whereas β-TCP block took 240 h for complete transformation to HAp. The porosity of HAp obtained from β-TCP block was found to be lower than that of HAp from α-TCP block. Diametral tensile strength of HAp from β-TCP block showed a significantly higher value than that of HAp from α-TCP block. It is therefore concluded that solubility of precursor affects the mechanical strength of the HAp block.