Papers by Keyword: Bioceramic

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Authors: C.S. Abreu, M. Amaral, Filipe J. Oliveira, José D. Santos, Rui F. Silva, J.R. Gomes
Authors: F.H.D. Pontes, Simone P. Taguchi, L.A. Borges, João Paulo Barros Machado, C. Santos
Abstract: Alumina ceramics have been used in dental prosthesis because it is inert, presents higher corrosion and shear resistance when compared to metals, excellent aesthetic, and mechanical resistance. In this work it was produced an infrastructure material for applications in dental crowns, obtained by glass infiltration in alumina preforms. Various oxides, among that, rare-earth oxide produced by Xenotime, were melted at 1450°C and heat treatment at 700°C to obtain the glass (RE-glass). The alumina was pre-sintered at 1100°C cut and machined to predetermine format (unidirectional indirect infiltration) and finally conducted to infiltration test. The alumina was characterized by porosity (Hg-porosity and density) and microstructure (SEM). The glass wettability in alumina was determined as function of temperature, and the contact angle presented a low value (<90º), showing that glass can be infiltrated spontaneously in alumina. The infiltration test was conducted at glass melting temperature, during 30, 60, 180, 360 minutes. After infiltration, the samples were cut in longitudinal section, ground and polished, and analyzed by XRD (crystalline phases), SEM (microstructure) and EDS (composition).The REglass presents higher infiltration height when compared to current processes (direct infiltration), and homogeneous microstructure, showing that it is a promising method used by prosthetics and dentists.
Authors: Sergey V. Dorozhkin, Oguzhan Gunduz, Faik N. Oktar
Abstract: Dense bioceramics made of pure hydroxyapatite (HA) was prepared and characterized. The cylindrical samples were compacted from HA powders of diverse pretreatments; namely, from spray-dried HA, calcined HA and mixtures thereof. The samples were prepared by a hydraulic press under different compaction loads both with and without auxiliary compounds (a binder and a lubricant). Both the total mass and geometrical dimensions of the prepared cylinders were measured. Then, the cylindrical samples were sintered at 1200 °C for 4 hours. After cooling down to ambient temperature, the sintered cylinders were weighed and their geometrical dimensions were measured once again. Mass decreasing and the shrinkage degree were calculated as a result. Afterwards, the compression strength of the sintered cylinders was measured by an Instron 5587 machine. Preparation of dense HA bioceramics possessing the highest possible compression strength was the purpose of this study. The necessary processing parameters were discovered.
Authors: Mohd Hamdi Bin Abdul Shukor, J.A. Toque, A. Ide-Ektessabi
Abstract: Wear resistance is an important mechanical property expected from coatings intended for any type of applications. Understanding of this quantity is very practical because in real situations, coatings are subjected to repeating loads experienced not in a gradual orderly fashion but abruptly and indeterminately. This study looked into the wear characteristic and adhesion behavior of calcium phosphate, a known bioceramics, and hopes to provide better understanding of these properties. Radio frequency-magnetron sputtering (RF-MS) was used to deposit thin film (CaP) on glass. The coatings were subjected to single-pass microscratch and multi-pass wear test while monitoring the depth, load and displacement in situ. The results have shown that the changes in the surface topography can give an indication of the wear resistance of CaP. Coatings with good adherence to the substrate have shown less alteration of its surface roughness, measured in terms of Ra values, even after several scratch passes. The study on the different parameters revealed that deposition time is the most influential factor in CaP wear behavior. This was attributed to its correlation with coating thickness. Analysis of variance (ANOVA) also suggested that the other sputtering parameters studied in the experiments (argon pressure and RF power) did not have very significant effect on the wear pattern of the CaP thin films.
Authors: Herman S. Mansur, Alexandra A.P. Mansur, Marivalda Pereira
Abstract: In the present work, natural coral from Brazilian reefs were studied according to their crystallography by X-ray diffraction and microstructure by Scanning Electron Microscopy (SEM/EDX). FTIR spectroscopy was also used to evaluate the chemical functionalities and major components present in the material. The SEM morphology results have shown a tri-dimensional coral structure with porous ranging from 50 to 200 µm. Aragonite was identified as the major crystalline phase through XRD analysis and FTIR spectroscopy. Strontium calcium carbonate, (Sr,Ca)CO3, was also identified by XRD analysis. After sintering at 900º/1h, the conversion from aragonite to CaO and calcite was observed. These results have endorsed the high potential application of natural coral materials as 3D scaffolds for biomedical application, because of calcium carbonate compounds can be converted to HA by hydrothermal and biomimetic coating processes.
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