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Calcite nano-particle is suggested as an extremely effective material in the biomedical due to their shape, non-toxic properties and being easily metabolized by cells. In clinical application, calcite nano- particle has to be useful for recovering the surface of tooth. The surface of tooth was often damaged due to wrong tooth care treatment, dental caries and periodontal disease. Because of tooth surface destruction, it could lead to dental hypersensitivity. It is desirable to find a suitable source for supplying calcium to fill in dentinal tubules and later regenerate the tooth surface. This study demonstrated the synthesis and characterization of calcite nano-particle for its application in dental hypersensitivity treatment. Cockleshell was found to be a suitable source to synthesize calcite. Using cockleshell as raw materials to produce calcite nanoparticle is meaningful for both environmental protection and biomedical application. Therefore, in this study, calcite nano-particle was synthesized using cockleshell as a reproducibility source of calcium carbonate (CaCO3) and chitosan as a size-reducing agent. X-ray Diffraction (XRD) was used to characterize phase composition of raw materials, as-prepared powder and calcined powder. Transmission Electron Microscopy (TEM) was used to evaluate the size and morphology of powder. Results indicated that calcite nano-particle with size about 50-100 nm could be obtained. It would be expected to consider for further studies in clinical application.

Abstract. Rice husk ash (RHA) obtained from agricultural by-product could be a potential source for partial cement replacement to produce concrete brick. In this study, primary RHA and RHA heat-treated at 500 o C were used to substitute cement in raw material mixtures. Preliminary analyses were conducted to evaluate some properties of RHA such as loss of ignition (LOI), morphology, chemical and phase compositions. X-ray Powder Diffraction (XRD) and X-Ray flourescence (XRF) results indicated that silica (SiO2) is the major component of RHA. Transmission Electron Microscopy (TEM) images showed that RHA particles were in polygonal shapes with diameter approximately from 300 nm -1 μm. Cement was replaced with RHA by weight at 10 %wt. The effects of RHA on the physical and mechanical properties of the aggregate cement bricks were investigated. Results demonstrated that the compressive strength of concrete bricks increased with age at curing and decreased as the percentage of RHA content increased. It is recommended that further studies should be carried out to achive optimum parameters for production of concrete brick in economic aspects.