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Hydroxyapatite Powder (hydroxyapatite + powder)
Selected AbstractsGrowth of ameloblast-lineage cells in a three-dimensional Matrigel environmentEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 2006Wu Li Enamel organ epithelial cells grow in culture as two distinct cell populations , either stellate-shaped or polygonal-shaped cells. The polygonal cells have an ameloblast cell phenotype and are difficult to grow in culture beyond two passages. This study was designed to determine the effects of a Matrigel three-dimensional (3D) environment on polygonal cells, as compared with stellate cells, derived from porcine tooth enamel organ. Enamel organs were dissected free from the unerupted molars of 30-kg pigs and then grown in LCH-8e media, either with or without serum. Cells grown in serum-free media were primarily polygonal shaped, whereas cells grown in media containing serum were stellate shaped. Both types of cells were grown in a 3D Matrigel matrix. In addition, polygonal-shaped cells were mixed with hydroxyapatite powder and transplanted subcutaneously into nude mice. Polygonal-shaped epithelial cells formed cell groups, similar to epithelial pearls, both in vitro and in vivo. The stellate-shaped cells, in contrast, did not form similar structures, but remained suspended in the Matrigel and gradually disappeared from the culture. These results suggest that a Matrigel environment, rich in basement membrane and matrix proteins, selects for polygonal-shaped ameloblast-lineage cells and induces the formation of epithelial pearls. [source] The erosive potential of flavoured sparkling water drinksINTERNATIONAL JOURNAL OF PAEDIATRIC DENTISTRY, Issue 2 2007CATRIONA J. BROWN Objective., The potential role of acidic drinks in the aetiology of dental erosion is well recognized. Whilst the wide-scale consumption of bottled waters is unlikely to contribute significantly to erosion, the role of flavoured sparkling water drinks is unclear. The aim of this study was to determine the pH, titratable acidity and in vitro erosive potential of a selection of these drinks drawn from the UK market to identify what dietary advice would be appropriate in relation to their consumption. Methods., pH was measured using a pH electrode and titratable acidity recorded by titration with 0.1- m NaOH. Erosive potential was assessed using an in vitro dissolution assay with hydroxyapatite powder and electron microscopic examination of surface enamel of extracted human teeth, following exposure to the flavoured sparkling waters for 30 min. Results., All of the flavoured waters tested showed appreciable titratable acidity (0.344,0.663 mmol) and low pH (2.74,3.34). In the hydroxyapatite dissolution assay, all of the waters demonstrated erosive potential (89,143%) similar to or greater than that of pure orange juice, an established erosive drink. Exposure of the extracted teeth to the flavoured waters resulted in surface changes consistent with erosive dissolution. Conclusions., Flavoured sparkling waters should be considered as potentially erosive, and preventive advice on their consumption should recognize them as potentially acidic drinks rather than water with flavouring. [source] The contribution of coating microstructure to degradation and particle release in hydroxyapatite coated prosthesesJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2002K. A. Gross Abstract Plasma-sprayed coatings of hydroxyapatite powder are widely used on hip replacements. Commercially, they are supplied by a large number of companies and thus offer different coating design philosophies. This study focuses on a retrieved prosthetic stem that exhibited coating loss on the femoral stem occurring concurrently with third-body wear. The purpose of the research was to establish possible links between the coating microstructure and the clinical findings. A coated stem and cup were sectioned and the cross section was prepared to reveal the coating microstructure. Characterization included X-ray diffraction, FTIR spectroscopy, and crystalline particle quantification within the coating. It was found that the coating has a high amorphous content that provides fast resorption. The amount of crystalline particles increased on the distal location of the stem, the threads of the acetabular shell, and was generally higher on the cup. Accelerated degradation illustrated how the coating may be a particle-generating source by preferential dissolution of the amorphous phase, possibly allowing liberation of crystalline areas and other particulates at the substrate-coating interface. Such particles mainly include the less soluble hydroxyapatide formed from unmelted particles in the plasma or recrystallisation in the coating, but may also include entrapped grit lodged in the substrate during the roughening process. This study accents the importance of coating microstructure in understanding coating resorption. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 106,114, 2002; DOI 10.1002/jbm.10090 [source] Design of Experiments (DOE) for the Optimization of Titania,hydroxyapatite Functionally Graded CoatingsINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 4 2009Valeria Cannillo Titania,hydroxyapatite functionally graded coatings were deposited on titanium alloy substrates by plasma spraying. Because it was necessary to spray together the titania and the hydroxyapatite powders to obtain the graded system, the first target of the present study was to optimize the process parameters in order to obtain a high-quality coating. A 23 Design of Experiments was applied to define the optimal values of plasma torch power, hydrogen flux, and spraying distance. This defined set of parameters (38 kW, 5 SLPM, and 90 mm, respectively) was used to spray the most promising graded coating, which was characterized and postheat treated. [source] | |||||||||||||