Effects of thermal treatment on injectability and basic properties of apatite cement containing spherical tetracalcium phosphate made with plasma melting method

We have previously prepared spherical-shaped tetracalcium phosphate (s-TTCP) with plasma melting method. We found that apatite cement (AC) containing s-TTCP showed excellent injectability from syringe and handling property when compared with AC that contained irregular-shaped TTCP (i-TTCP). However, transformation of AC containing s-TTCP (s-AC) to apatitic mineral was suppressed and thus mechanical strength of set s-AC was low. In the present study, thermal treatment was attempted on s-TTCP to convert heat decomposition products formed in s-TTCP during plasma melting process to TTCP. X-ray diffraction (XRD) analysis revealed that some heat decomposition products in s-TTCP converted to TTCP when s-TTCP was heated at 1,500°C for four hours and quenched at room temperature (q-TTCP). AC containing q-TTCP transformed to apatitic monolith and showed equivalent mechanical strength similar to AC that contained i-TTCP —without sacrificing excellent injectability from syringe and handling property. Based on these findings, we concluded that AC containing q-TTCP would benefit patients since it delivered excellent injectability without sacrificing basic setting properties of AC.