Browsing by Author "Shibli, SMA"

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    Biomimetic deposition of hydroxyapatite on titanium with help of sol-gel grown calcium pyrophosphate prelayer
    (MATERIALS RESEARCH INNOVATIONS, 2011) Sureshbabu, S; Komath, M; Shibli, SMA; Varma, HK
    The biomimetic method is a cost effective, low temperature route for coating hydroxyapatite on titanium bone implants so as to provide an osteointegrating interface. However, biomimetic coatings have the limitations of poor adhesion and lower growth rates. This work investigates the role of a prelayer of calcium pyrophosphate made through sol-gel technique in growing adherent and thick layer of biomimetic hydroxyapatite over titanium surface. Cleaned titanium substrates were dip coated in a calcium-phosphate-citrate sol and calcined at 650 degrees C to form an adherent calcium phosphate layer. These were then subjected to biomimetic processing in 1.5 simulated body fluid for 7-14 days. The prelayer and the biomimetic layer were analysed for micromorphology (using SEM) and chemical phase (using X-ray diffraction, Fourier transform infrared spectroscopy and energy dispersive X-ray spectroscopy). Thickness measurements were performed on an optical profilometer and the adhesion was assessed through a microcombi scratch tester. The prelayer showed petal-like morphology, whereas globular particles were seen in the biomimetic growth. The prelayer had a thickness of 3.6 mu m and was found to contain calcium pyrophosphate, with calcium titanate at the interface. The phase in the biomimetic layer was identified to be hydroxyapatite, with a growth rate of 5.3 mu m/day. The scratch test gave the delamination load for this layer to be 6.23 N. Results show that it is possible to obtain adherent hydroxyapatite layer on the titanium surface at a faster rate by combining the sol-gel coating and the biomimetic growth technique.
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    Development and evaluation of two PVD-coated beta-titanium orthodontic archwires for fluoride-induced corrosion protection
    (ACTA BIOMATERIALIA, 2011) Krishnan, V; Krishnan, A; Remya, R; Ravikumar, KK; Nair, SA; Shibli, SMA; Varma, HK; Sukumaran, K; Kumar, KJ
    The present research was aimed at developing surface coatings on beta titanium orthodontic archwires capable of protection against fluoride-induced corrosion. Cathodic arc physical vapor deposition PVD (CA-PVD) and magnetron sputtering were utilized to deposit thin films of titanium aluminium nitride (TiAIN) and tungsten carbide/carbon (WC/C) coatings on beta titanium orthodontic archwires. Uncoated and coated specimens were immersed in a high fluoride ion concentration mouth rinse, following a specially designed cycle simulating daily use. All specimens thus obtained were subjected to critical evaluation of parameters such as electrochemical corrosion behaviour, surface analysis, mechanical testing, microstructure, element release, and toxicology. The results confirm previous research that p titanium archwires undergo a degradation process when in contact with fluoride mouth rinses. The study confirmed the superior nature of the TiAIN coating, evident as many fewer changes in properties after fluoride treatment when compared with the WC/C coating. Thus, coating with TiAIN is recommended in order to reduce the corrosive effects of fluorides on beta titanium orthodontic archwires. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.