Key Engineering Materials Vols. 284-286

Abstract: The effect of different particle sizes on the flexural strength and microstructure of three different types of hydroxyapatite (HAp) powders was studied. The powder characteristics of laboratory synthesized HAp powder (Lab1 and Lab2) were obtained through a wet milling method, and the median particle size and the specific surface area of powders are different with the dryness period. The median particle sizes of Lab1 and Lab2 are 0.34 µm and 0.74 µm, and the specific surface areas of Lab1 and Lab2 are 38.01 m2/g and 19.77 m2/g. The commercial HAp had median particle size of 1.13 µm and specific surface area of 11.62m2/g. The different powder characteristics affected the slip characteristics, and the flexural strength and microstructure of the sintered porous HAp bodies are also different. The optimum value for the minimum viscosity in these present HAp slip with respect to its solid loading and the optimum amount of the deflocculant were investigated. The flexural strengths of the porous HAp ceramics prepared by heating at 1200°C for 3 hrs in air were 17.59 MPa for Lab1 with a porosity of 60.48％, 10.51 MPa for Lab2 with a porosity of 57.75％, and 3.92 MPa for commercial HAp with a porosity of 79.37％.

Abstract: Porous calcium metaphosphate granules for bone fillers were prepared by starch consolidation with baking powder and surfactant. Paste for foaming was prepared by the mixing of calcium metaphosphate powder and water with the various amount of starch (10~20㎛ size), where solid contents 30%, 45%, 60% of the paste. In order to obtain the optimum micro/macro porous structure, the appropriate contents of baking powder and surfactant at a fixed content of starch were examined. In order to examine the content of baking powder on pore morphology, the baking powder was added 60, 180, and 300 wt% of the paste at fixed content of starch. And then, in order to investigate the effect of surfactant on porous structure, surfactant was added 0.035, 0.1, and 0.16 wt% of paste weight at fixed content of starch and baking powder. Foaming was conducted using microwave method, and foamed samples were sintered at 900 °C. The sintered porous blocks with starch only showed uneven and closed macro pores without any micro pores. However, the sintered porous blocks with starch, baking powder, and surfactant showed homogeneous micro and macro porous structures ranging 20~60, and 300~1000 ㎛ in pore size, respectively. The porosity was increased with the increase of surfactant up to about 70 %.

Abstract: Carbonate apatite form that has three-dimensional fully interconnected pore was prepared based on so-called ceramics form preparation method. First, a-tricalcium phosphate (a-TCP) form was prepared by immersing polyurethane form into a-TCP powder suspension. The form was heated in an electronic furnace for sintering a-TCP as well as for burning out of the polyurethane form. Then hydrothermal treatment was preformed at 200 degrees in the presence of saturated sodium bicarbonate for 24 hours. Although the mechanical strength of the carbonate apatite form was poorer when compared with a-TCP form, we found that the hydrothermal treatment of a -TCP form result in the formation of B-type carbonate apatite form without changing the ideal morphology of a -TCP form.

Abstract: In this study we focus on the use of coral Porites Lutea and the various treatments used to remove proteins while assessing the impact of the various removal methods on the in vitro and in vivo coral behavior. No significant differences were observed in vitro among all materials. In vivo, no histological differences were observed between BiocoralÒ and samples treated by either hydrogen peroxide or a thermal procedure. The implants made from supercritical fluid treated coral were more resistant to resorption (50% more resistant after one month).

Abstract: In this study, we examined in vivo performance of newly developed hydroxyapatite (HA)ceramics, which is obtained by sintering the HA powder mixed with CaO·MgO·SiO2-based glass at 1000°C (liquid phase sintering). Bioactivity of this glass-containing HA was evaluated compared with the control HA by mechanical test and histological examination. The glass-containing HA showed higher bone-bonding strength than the control HA throughout the experimental period. Light microscope and backscattered scanning electron microscope (SEM) showed that the both kinds of implants bonded directly to the bone. High bioactivity in vivo, especially in the early period after implantation, of this newly developed HA was confirmed, which is one of the essential requirement for optimal bone substitutes.

Abstract: The adsorption behaviour of sodium ampicillin to dense and porous hydroxyapatite as been extensively studied through the obtention of an adsorption isotherm. This isotherm was produced at body temperature, and a wide range of antibiotic solutions was used. The adsorption behaviour was measured by UV spectroscopy. The shape of the isotherm for the two forms of the material, dense and porous, indicates that the adsorption behaviour of the antibiotic seems to be different; however, this is due to the adsorption taking place within the pores of the porous material, thus showing a larger amount of antibiotic adsorbed.

Abstract: The demand from patients for aesthetic in posterior teeth restoration has been increasing in recent years. As an alternative to metal alloy restorations used in posterior tooth, aesthetical materials such as ceramics have been more often utilized. Resin cement, a derivative from dental composite, based on the combination of bis-GMA and inorganic filler is used to fixate these ceramic restorations to posterior teeth. Similar to resin composite, incorporated antibacterial agents to resin cement can be an effective way to increase the aesthetic restoration durability. Resin cements C&B® (Bisco) and Fill Magic Dual Cement® (Vigodent) were used in the present study. For experimental resin cement, Triclosan was incorporated to the base cement paste. Samples were investigated by Scanning Electron Microscopy coupled to EDX microprobe (SEM/EDX) and FTIR spectroscopy. The results have demonstrated that the incorporation of antibacterial agents to resin cement is possible through the developed procedure.

Abstract: The purpose of this study was to investigate the in vitro degradation and release behaviors of calcium phosphate powders (Ca/P) containing Chinese Medicine for bone graft. Two kinds of Ca/P powders, one with the Chinese Medicine, Salvia Miltiorrhiza Bunge (SMB) and the other with Polyacrylic Acid (PAA) and SMB, were soaked in simulated body fluid (SBF) for up to 150h. The in vitro release of SMB was measured by UV-VIS spectroscopy. The Ca2+ concentrations and pH of SBF soaked Ca/P powders were measured by AAS and pH meter. TA and XRD were employed to analyze various Ca/P powders before and after soaked in SBF, respectively. The results demonstrated that a faster SMB release occurred during the first 24 hours, while a slow release was sustained up to150h. Furthermore, the released of SMB in Ca/P-PAA-SMB was faster than that of Ca/P-SMB. It was concluded that a controllable release of Chinese Medicine from Calcium phosphate may be carried out by the addition of suitable surfactant. Accordingly, calcium ions were released into SBF, which was benefit for bone tissue repairing and reconstructing. Additionally, the TA results showed that there was 1.66% SMB released from Ca/P-SMB-PAA powders. XRD confirmed that various Ca/P powders possessed poorer crystallinity and smaller grain size.

Abstract: One type of potent aminobisphosphonate (Zoledronate) has been chemically associated onto b-tricalcium phosphate [b-TCP] and calcium deficients apatite [CDA]. Two different association modes have been observed, according to the nature of the Calcium Phosphate [CaP] support and/or the initial concentration of the Zoledronate solution. b-TCP appears to promote Zoledronate-containing crystals formation. On the other hand, at concentrations < 0.05 mol.L-1 CDA seems to undergo chemisorption of the drug through a surface adsorption process, due to PO3 for PO4 exchange, which is well described by Freundlich equations. At concentrations > 0.05 mol.L-1, crystalline needles of a Zoledronate complex form onto the CDA surface. The ability of CDA to release Zoledronate, resulting in the inhibition of osteoclastic activity, was shown using a specific in vitro bone resorption model.

Abstract: Hydroxyapatite (HA) coating applied on metallic orthopedic joint implants can improve bone apposition, presumably through selective protein adsorption from blood plasma. However, the detailed interaction mechanism of HA coating with serum proteins remains to be largely elucidated. Protein adsorption behavior of a biomimetic apatite (BAp) coating in bovine calf serum and alpha calf fraction was investigated in this study. Plasma sprayed HA (PSHA) coating was tested in alpha calf fraction. The microstructure and composition of the coatings before and after serum incubation were characterized and the proteins adsorbed during the incubation were extracted from the coatings and analyzed. Microstructural transformation of the BAp coating accompanied by selective serum protein adsorption was observed after incubation in both media. The total protein amount adsorbed by the BAp coating in alpha calf faction was about three times that of the PSHA coating. To test the potential use of BAp coating as a carrier of therapeutic agents, interaction between the BAp coating and transforming growth factor (TGF)-β1 was studied. The growth factor was successfully loaded onto the coating in a sodium acetate buffer. Because of its high affinity to the coating, TGF-β1 could not be easily eluted in a bovine serum albumin containing solution but could be recovered after coating dissolution in acid. The strong protein adsorption property of the BAp coating was found to be due mainly to its unique nanoporous structure. The BAp coating can serve as an ideal carrier of therapeutic agents for aiding in the healing of bone and soft tissues.