Evaluation of calcium aluminate/calcium phosphate based biocements as root-end filling material

Abstract

Nano-particles of pure single phase calcium aluminate (CA) were prepared via solid state reaction at high temperature. An ultra-pure nano-size hydroxyapatite (HA) prepared by sol-gel method was used to formulate a composite of 1:1 CA: HA. Setting times, micro-hardness, bulk density, calcium ion and phosphorus ion concentration, XRD, FTIR and scanning electron microscopy (SEM) were investigated. The results showed that the substitution of 50% by weight of pure calcium aluminate cement (CA) by nano-size hydroxyapatite (HA) has a retardation effect on setting process. The use of artificial saliva solution as hydration medium enhances the hydration process of both synthesized calcium aluminate based materials due to the formation of more hydrated compounds. Curing of calcium aluminate cement in hot and humid conditions, resulting in hardness loss and high porosity due to the conversion process, in which the compounds CAH10 and C2AH8 (hexagonal crystals) are converted into the more stable compound C3AH6 (cubic crystals). The SEM studies indicated that the presence of nano-particles of hydroxyapatite in CA/ HA composite facilitated the precipitation of hydroxyapatite-like active layer, suggesting that pure CA cement has some distinctive physico-mechanical properties make it suitable for use as root end filling materials in dental applications.