Development of an apatitic calcium phosphate cements: effect of liquid/powder ratio on the setting time

Abstract

Calcium phosphate cement (CPC) sets in situ to form resorbable hydroxyapatite with chemical and crystallographic similarity to the apatite in human bones, hence it is highly promising for clinical applications. Among the clinical requirements for calcium phosphate bone cements are initial setting time and final setting time. α-tricalcium phosphate (α-TCP) and hydroxyapatite (HA) were mixed with dicalcium phosphate dehydrate (DCPD) to form the cement powder which is mixed with aqueous solutions of 3% Na 2 HPO 4 .2H 2 O in weight at four different liquid-to‐powder ratios (0.35, 0.40, 0.45 and 0.50 mL/g). The cement powder, on wetting with the medium, formed a workable putty. X-ray diffraction (XRD), Energy dispersive X-ray spectroscopic (EDS) , transmission electron microscope (TEM) and scanning electron microscopy (SEM) techniques were employed to evaluate the phase composition and surface morphology of the cements. The results revealed similar phase composition for all samples before and after soaking in distilled water at 37°C. According to the results, it is shown that almost complete transformation of cements in calcium-deficient hydroxyapatite (CDHA) occur after soaking 7 days in destilled water with nanosized rod-like hydroxyapatite crystals. Also by reducing the L/P ratio from 0.50 to 0.35, initial and final setting times of the CPCs decreased 11 and 10 minutes respectively.