Papers by Author: Xiang Hui Lan

Abstract: The amorphous calcium phosphate (ACP)/tricalcium silicate (Ca3SiO5, C3S) composite powders were synthesized in this paper. The exothermal behavior of C3S determined by isothermal conduction calorimetry indicated that the ACP could be synthesis by chemical precipitation method during the induction period (stage II) of C3S. The composite powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The results indicated that nanosized ACP particles deposited on the surface of C3S particles to form core-shell structure at pH=10.5, and the nCa/nP of ACP could be controlled between 1.0 and 1.5. The core-shell structure is stable after sintered at 500 oC for 3 h to remove the β-cyclodextrin (β-CD). As compared with the irregular C3S particles (1~5 μm), the composite powders particles are spherical with a diameter of 40~150 μm. Therefore, to obtain the smaller size of composite powders, it is expected to avoid the aggregate of C3S particles in the aqueous solution by addition of dispersant. As compared with C3S, the composite powders may contribute better injectability, strength and biocompatibility.

Abstract: The bioactivity of potassium titanate whiskers (PTW) was evaluated by soaking in simulated body fluids (SBF, Kokubo solution). At first, PTW was chemically treated by 1 M HCl and 1 M NaOH solutions at 60 oC for 48 h, respectively. Then PTW before and after treated were soaked in SBF solution and cultured at 37 oC for different times. The apatite deposit on PTW was examined by FTIR and SEM/EDX. The results showed that there was not apatite deposit on the raw PTW even after soaked for 14 days while apatite appeared on the treated PTW after soaked for only 7 days. This implies that treatment by HCl/NaOH solutions can improve the in vitro bioactivity of PTW. The possible mechanism is that more Ti–OH groups occur after treatment and induce Ca2+ and PO4 3- aggregate and accelerate to deposit of apatite. The bioactive PTW with good biocompatibility is a potential candidate as reinforcing agent to improve the mechanical properties of calcium phosphate ceramics or cements.

Abstract: The aim of this study was to evaluate the suitability of CaF2 doping tricalcium silicate (Ca3SiO5, C3S) as dental restorative materials. The solid state reaction method was used to prepare CaF2 doping C3S (F-C3S) using CaCO3, SiO2 and CaF2 as the starting materials. The in vitro bioactivity, the rate of heat evolution and the compressive strength were investigated. The in vitro bioactivity was examined by soaking the pastes in simulated body fluid (SBF). The FTIR and SEM results indicated the hydroxycarbonate apatite (HCA) layers of F-C3S pastes and pure C3S pastes occurred after soaking for 1 day and 3 days, respectively. The difference in bioactivity was attributed to the formation of F-substituted apatite, which has a Ksp lower than HCA. As compared with the pure C3S, the rate of heat evolution during the hydration of F-C3S was slower. This was avail to the dimensional stability of dental restorative materials. The pastes of F-C3S had a lower early compressive strength in the early stage, but a higher compressive strength in the later stage. Our results indicated that F-C3S would be bonded better to the teeth because of the earlier formation of HCA and the higher later compressive strength. F-C3S may be a progressive candidate for dental restorative materials.