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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 CAH 10 and C 2 AH 8 (hexagonal crystals) are converted into the more stable compound C 3 AH 6 (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.

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Nano particles made of pure single phase Mineral trioxide [tricalcium silicate (C 3 S)] and Tetracalcium phosphate (TTCP) bio ceramics were prepared via solid state reaction at high temperature. Setting times, compressive strength, pH, XRD, FTIR and scanning electron microscopy (SEM) were investigated. Cytotoxicity and antibacterial activity of both C 3 S and TTCP to human gingival fibroblasts were studied. Both C 3 S and TTCP compounds undergo hydration reaction when mixed with distilled water. A delayed setting time and very poor mechanical properties for TTCP were detected compared to those of C 3 S phase. The nano-structure C 3 S bio ceramic was found to be completely safe to BHK cells compared with TTCP. The prepared C 3 S and TTCP pastes were applied to the demineralized dentin specimens for seven days. The ultramorphology of dentin revealed that both C 3 S and TTCP are successful in dentinal tubules occlusion, thus they are beneficial for dental application in the treatment of teeth hypersensitivity.

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