Papers by Keyword: Apatite

Abstract: Effect of heat-treatment temperature on the osteoconductivity of the apatite derived from bovine trabecular bone was investigated. Three different heat-treatment temperatures (600, 800 and 1000 oC) were adopted in the experiment and their effects on the physical properties of apatite granules, which could affect on the osteoconductivity, were evaluated. The content of carbonate ions in the apatite structure was assessed by FT-IR and its crystallinity was evaluated by X-ray diffractometry. The microstructure was assessed by field emission electron microscopy. Apatite granules heat-treated at 600 oC and 1000 oC were implanted into the calvaria of New Zealand White rabbit for 4 weeks, respectively, and the undecalcified ground histologic specimens stained with multiple staining method was observed. As increasing the heat-treatment temperature, the crystal size and crystallinity of the apatite increased while the content of carbonate ions decreased. The apatite granules heat-treated at 600 oC showed much better osteoconductivity comparing to that heat-treated at 1000 oC. The results were explained in terms of the physical properties of apatite which could affect to the osteoconductivity.

Abstract: Sulfonic groups (-SO3H) were covalently attached on different polymeric surfaces enabling them to induce apatite nucleation, for developing bioactive apatite-polymer composites with a bonelike 3-dimensional structure. High molecular weight polyethylene (HMWPE) and ethylene-co-vinyl alcohol co-polymer (EVOH) were used. The polymers were soaked in two types of sulphate-containing solutions with different concentrations, sulphuric acid (H2SO4) and chlorosulfonic acid (ClSO3H). To incorporate calcium ions into to the sulfonated polymers, the samples were soaked in a saturated Ca(OH)2 solution for 24 hours. After soaking of the samples in a simulated body fluid (SBF), formation of an apatite layer on both surfaces was observed. The results obtained prove the validity of the proposed concept and show that the -SO3H groups are effective on inducing apatite nucleation on the surface of these polymers.

Abstract: The bioactivity of Ti6Al4V induced by SSPB (supersonic particles bombarding) and alkali treatment was investigated in this work. More coarse surfaces were formed by SSPB and alkali treatment, which led to better bioactivity than that by only alkali treatment. Apatite began to appear on the surface of specimen only after 1 day of immersion in 1.5 SBF. As time passed, they gradually covered the whole surfaces. After 7 days of soaking in vitro, apatite formed and covered all the surfaces of the titanium alloys, and they packed very densely and uniformly. EDS and XRD results proved all the new-formed phases were composed of a carbonate containing hydroxyapatite with small crystallites and defective structure. As a result, SSPB treatment might be an effective way to enhance the bioactivity of titanium alloys for implantation.

Abstract: A titanium base alloy and a cobalt base alloy have been subjected to a biomimetic process. Samples of titanium and cobalt alloys have been immersed in 10M and 5M NaOH solutions, respectively, then the samples have been heat treated and finally, immersed in either a simulated body fluid (SBF) with ionic concentration close to human blood plasma or in a simulated body fluid with an ionic concentration 1.5 times that of the SBF (1.5SBF) for a period of 21 days. An apatite layer has been observed after the immersion of the samples in SBF for both Ti and Co base alloys. The apatite layer observed on the Ti alloy samples is more homogeneous and thicker than that observed on the Co alloy samples. However, the apatite layer on both samples is not continuous and homogeneous along the surface. The layer of apatite formed is thicker on samples immersed in 1.5SBF. This is attributed to the higher ion concentrations, mainly of calcium and phosphorus. The Ca/P ratios measured in the apatite layers are close to that of bone.

Abstract: Biphasic calcium phosphate (BCP) bioceramics, for use as resorbable bone substitutes, containing both isolated macropores and interconnected micropores, have been fabricated by sintering, using naphtalen particles as a porogen to produce macropores. The resulting ceramics contain ~ 45% macropores and various amounts of microporosity. Mechanical properties (compression and bending strength, toughness and hardness) have been measured and modeled by combining two approaches, at two different scales: the one describes the mechanical properties of a partly sintered stacking of grains, supposed to account for the interconnected microporosity, the other one holds in the case of closed and isolated macropores within a continuous matrix. The material is then represented as a quasi-continuous matrix containing macropores, the matrix being itself microporous. The model also considers that fracture always initiates on a macropore, which allows to set a correspondence between fracture toughness and fracture stress equations. The mechanical tests performed on the sintered ceramics tend to validate the modeling approach.

Abstract: Porous calcium phosphate ceramics (apatite and TCP) with wood-like microstructures, analogous to that of silicified wood, were prepared from natural woods as templates. The production of these ceramic woods was performed by the following process: (1) infiltration with an ethanol solution containing tri-ethyl phosphate and calcium nitrate tetra-hydrate into wood specimens, (2) drying to form a calcium phosphate gel in the cell structure, (3) firing in air to form apatite and TCP. The microstructure of the obtained ceramic woods retained the same structure as that of the raw woods: with the pore sizes corresponding to those of the original wood, and the major pores being unidirectionally connected.

Abstract: Amorphous calcium silicate coating on a metallic titanium substrate for hard tissue replacement was prepared by a sol-gel method. Calcium silicate film was deposited on a titanium substrate by a spin-coating technique and subsequently heated at 500°C for 2 h in air. The deposited film, which was dense, had thickness of about 800 nm and strongly adhered to the substrate. Biomimetic apatite-forming ability of the deposited films was examined by soaking in simulated body fluid (SBF). Thin film X-ray diffractometry and scanning electron microscopy showed the formation of apatite on the surface after 10 days of soaking in SBF.

Abstract: Present study evaluated the feasibility of apatite monolith preparation from calcium sulfate monolith using ammonium phosphate solution. We found that calcium phosphate monolith transforms to apatitic monolith without changing its original morphology when a proper temperature and a proper phosphate solution was selected. Prepared apatite was B-type carbonate apatite with low crystallinity. Although mechanical strength of the apatite monolith was lower than original calcium sulphate monolith, we concluded present method may be useful for the fabrication of apatite monolith since we can prepare different shape of apatite monoliths based on the setting reaction of calcium sulphate and compositional transformation to apatitic mineral.

Abstract: Glass-ionomer cements (GIC) have been used in dentistry for over 30 years. In the past ten years they have also been developed for use as medical grade bone cements. However, concerns have been raised over the biocompatibility of GIC’s in non-dental applications. The release of Al3+ ions from the cement has been related to localized poor bone mineralisation and neurotoxicity. There is a need therefore to develop Al2O3-free cements. One potential route is the substitution of Al2O3 with Fe2O3 in the glass. An Fe2O3-based glass for use in GIC‘s was fabricated. The glass was found to differ considerably compared to the traditional amorphous Al2O3-based glasses. XRD demonstrated a highly crystalline morphology containing magnetite and apatite which was confirmed using electron microscopy. It was predicted that the reduction in Al concentration in the glass would improve the biocompatibility of the resulting cement.

Abstract: Ethylene-vinyl alcohol copolymer (EVOH), poly(ethylene terephthalate) (PET) and polyethylene (PE) were modified with calcium silicate on their surfaces by a sol-gel method, before or after glow discharge treatment in O2 gas, soaked in a simulated body fluid (SBF) and implanted into knee bone of a rabbit. EVOH and PET formed nano-sized bonelike apatite uniformly on their surfaces in SBF, without being subjected to the glow discharge, and bonded to the living bone of the rabbit, whereas PE formed the apatite only sparsely even when being subjected to the glow discharge. Three dimensional fabrics with open spaces in various sizes of the former fibers modified with the calcium silicate might be useful as bone substitutes.