On Possibly Bioactive Cp Titanium Implant Surfaces

Author : Mohammad Mohsin Hossain
Publisher :
ISBN 13 :
Total Pages : 538 pages
Book Rating : 4.:/5 (813 download)

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Download or read book Investigation on the Surface Modification of Titanium Based Alloys for Improved Bioactivity written by Mohammad Mohsin Hossain and published by . This book was released on 2012 with total page 538 pages. Available in PDF, EPUB and Kindle. Book excerpt: Titanium-based engineering materials are currently considered to be the best artificial implant materials because of their good mechanical strength, resistance to corrosion, and their nontoxic compatibility with the stable oxide, TiO2. Ti6Al4V alloy is biologically inert, showing limited interaction with human tissue to their native oxide surface, which generally results in mechanical fixation. If the material is able to interact directly with tissue through chemical bonding, thus leading to a bioactive fixation, this will make a better and stronger implant for the promotion of cell attachment and migration and bone growth. Surface modification can improve the properties of surface oxide, leading to the formation of a stable oxide layer on the alloy's surface, and thus resulting in greater bioactivity. Surface modification is performed through surface chemical treatments, coatings deposition and chemical and thermal oxidation at a variety of process temperatures. The acid-alkaline-treated surface shows rougher, higher wettability and the presence of oxide of TiO2, as per the averaged results. In a comparison of roughness, wettability, and surface chemistry, no differences are observed between the original and solvent-treated surfaces. The crystalline structure of the surface treated samples reveals alpha and beta phases of Ti6Al4V alloy. However, the alpha 110 peak has only appeared on acid-alkaline substrate. This appearance is probably caused by a change of orientation of the crystallographic plane. Bioactivity results show no differences in Ca-P deposition between the surfaces, leading to CaHPO4, Ca/P~1.0. Some clusters deposit only on the original and solvent-treated surfaces which contain higher Ca-P than the surfaces in the non-cluster region, as observed by SEMEDS. Chemical oxidation treatments are conducted on the original surfaces by the H2O2, 37°C and H2O2, 80°C. Crystalline phases are generally associated with titanium alpha-beta, and a few with anatase and rutile. All the oxidised surfaces are defected by the presence of pores. Ti peaks are seen on the surfaces oxidised by H2O2, 37°C but no longer seen on the surfaces oxidised by H2O2, 80°C, except on the oxidised original surface. TiO2 concentrations are found quantitatively in the Ti 2p and O 1s spectra. A hydroxyl-rich oxides concentration is found at similar levels on all the oxidised surfaces. The oxidised acid-alkaline surface appears to be rougher than the other oxidised surfaces but the effects on the surface hydrophilicity are similar. Bioactivity results show a higher concentration of Ca-P deposits, leading to hydroxyapatite, Ca/P~1.6±0.1. The Ca-P deposition in SBF is increased from 3 to 14 days, as observed by XPS. Thick cluster layers are observed on the oxidised surfaces of the samples incubated for 14 days; these are composed of O, Ca and P; Ca/P~1.5, as observed by SEMEDS. Coating depositions of Ti and TiO2 are performed on the solvent-treated surface. XPS results show no Ti peaks present on the TiO2-deposited surface. The TiO2-deposited surface appears to be rougher and less hydrophilic than other surfaces. No significantly different Ca-P depositions are found on the deposited surfaces as results of CaHPO4 and Ca/P~1.0, which do not exhibit a good bioactive response. The chemically oxidised surfaces show a similarly roughened effect on all the oxidised surfaces. The oxidised Ti- and TiO2-deposited surfaces appear to be more hydrophilic than the oxidised solvent-treated alloys. The chemically oxidised surfaces reveal that Ca-P depositions increase, leading to hydroxyapatite, Ca/P~1.6±0.1 and that there are no differences in the oxidised deposited surfaces of any of the samples incubated from between 3 to 14 days. The Ca-P depositions on the oxidised deposited surfaces are found to have almost half the value of those on the oxidised solventtreated surfaces. The effects of thermal and chemical oxidation on the Ti-deposited samples are investigated. The crystalline structure is transformed from anatase to rutile in an increasing thermal temperature treatment of up to 800°C. At higher magnification, a thin layer with a porous structure is observed on the chemically oxidised surfaces. Shiny oxide layers are seen on the thermally oxidised surfaces. The concentration of atomic oxygen increases as the thermal temperature is increased from 100°C to 800°C, as observed by EDS. The surface chemistry results show that the content of chemically and thermally oxidised surfaces comprises hydroxyl-rich oxides and hydroxyl-poor oxides, respectively. Bioactivity results show that the chemically oxidised surface is able to deposit more Ca-P, leading to the formation of hydroxyapatite, Ca/P~1.7±0.1. However, the thermally oxidised surfaces deposit Ca(H2PO4)2 and, CaCO3 and P2O5 at temperatures of 100°C, 400°C and 800°C, respectively, at Ca/P~0.5. It has been conclusively proved that Ca-P depositions are dependent on the presence of hydroxyl-rich oxides. Apatite nucleation can be formally initiated at the stage of the completion of Ca-P depositions and can actively promote bone-growth after the material has been implanted.