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Background: Due to the topical fluoride treatment, fluorapatite (FAp) and calcium fluoride are forming on a dental enamel surface. Different researches concerned in oral biology, prevention and treatment have studied hydroxyapatite (HAp) and FAp dissolution in addition to precipitation reactions since these materials are essentials in dental hard tissues. However, FAp is less soluble phase amongst the calcium phosphates and has more complicated equilibria. Objective: This study has indicated the solubility isotherms, S of CaF, and the solubility of FAp and HAp using the titration method. Design: In this study, a titration with pH adjustment method using diode laser-scattering system had been performed to monitor any solid increment addition where the material has been reprecipitated and detected by the endpoint represented by the output signal. Materials and Methods: The composition and the morphology of the precipitate were studied and the Ca/P ratio was also determined. In addition, a comparative study of the solubility isotherm of the CaF2, HAp, and FAp were performed among wax-coated apparatus and an uncoated vessel experiment. Results: The results showed that Ca/P ratio of the precipitate has decreased steadily at lowering pH values. In addition, FAp has shown slightly less solubility than HAp at pH < 3.9 and the particles were single crystal with rod-like morphology at pH 4.1 and polycrystalline at pH < 3.6. Conclusion: Wax-coated apparatus helped to avoid any expected interferences, the titration was successfully validated, while solutions rich with fluoride were acted as modifying agents to the solubility of HAp. [ABSTRACT FROM AUTHOR]

Background: Owing to the topical fluoride treatment, calcium fluoride and fluorapatite (FAp) are forming on a dental enamel surface. Many in oral biology, prevention and treatment have studied hydroxyapatite (HAp) and FAp dissolution. Some focused on precipitation reactions since these materials are prerequisites in dental hard tissues. Nonetheless, FAp is less soluble phase amongst calcium phosphates and has more complicated equilibria. Objective: This study aims to validate a suitable method for checking HAp and FAp behaviours. Design: A titration with pH adjustment method using diode laser-scattering system had been performed to monitor any solid increment addition where the material has been reprecipitated and detected by the endpoint represented by the output signal. Materials and Methods: The composition and the morphology of the precipitate were studied and the Ca/P ratio was also determined. A comparative study of the solubility of the CaF2, HAp, and FAp were performed among wax-coated apparatus and an uncoated container experiment. Results: These showed that Ca/P ratio of the precipitate has decreased steadily at lowering pH values. In addition, FAp has shown slightly less solubility than HAp at pH < 3.9 and the particles were single crystal with rod-like morphology at pH 4.1 and polycrystalline at pH < 3.6. Conclusions: The titration was successfully validated where wax-coated method had avoided any interference with F -containing test solutions. [ABSTRACT FROM AUTHOR]

In the cement industry, researchers have worked on blending cement with supplementary cementitious materials (SCMs) to enhance the mechanical properties of concrete. For technical and environmental reasons, previous studies have recommended that concretes be designed with less ordinary Portland cement (OPC). Other researchers encourage the use of thermal treatments at the precast stage. In this work, high volumes of various SCMs other than OPC were used to prepare five cement formulations, including a control sample. Initial tests of three hydraulic binders were performed to check their suitability before mixing cement samples. The samples were treated in water, air, hot water, and hot air curing (HAC) conditions after demoulding. The study showed that a combination of rice husk ash (RHA) and fly ash (FA) with OPC in the binder matrix, cured under HAC conditions, gave the best compressive and flexural strength results with the lowest water absorption. [ABSTRACT FROM AUTHOR]