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Hydroxyapatite (HAP) ceramics are used extensively in different medical applications, as biomaterial for repair or replacement of bone tissues since it resembles mineral component of bone and teeth. However, synthetic HAP exhibits low fracture toughness due to its lack of strength and brittleness, thereby providing an obstacle to its application in implants that must withstand high loads. Improvement of the mechanical properties can be achieved by the incorporation into resistant oxide phase, e.g. Zirconia partially stabilized by calcia. The preparation of homogeneously distributed zirconia- hydroxyapatite composites can be accomplished using a co-precipitation process of precursor reagent solutions. The present study describes the preparation and characterization of two fine composite powders of zirconia and hydroxyapatite intended for biomedical implants. The composites were evaluated using XRD, FT-IR and TG-DTA. 

Graft copolymerisation of methyl methacrylate (MMA) onto Chitosan using cerium (IV) as the initiator was studied with varying concentrations of MMA. Under controlled conditions, 49 % grafting (calculated from Thermogravimetric analysis, TGA) with a grafting yield of 92 % was achieved. FTIR, thermal and XRD techniques were used to confirm the formation of the grafted copolymer. Grafting caused a significant decrease in the mechanical strength of the polymer. The grafted products demonstrated improved swelling at pH 7.4 and pH 1.98 compared to the original Chitosan. The glass transition temperature (Tg) and the initial decomposition temperature were enhanced for the grafted copolymers. The grafting did not affect the hydrophilicity of chitosan, as evident from the contact angle studies. The grafted polymers were found to be non-cytotoxic and blood compatibile. The properties of chitosan could be tailored by the concentration of the graft. The graft copolymer could be made into microspheres for possible drug release applications.

Orthodontic archwires are designed to move teeth with light continuous forces. Mechanotherapy depends on both the elastic behavior of the material and the biochemical reaction of the teeth. Stainless steel A. J. Wilcock (Australian) wires have been the backbone of Begg treatment since its inception. During the last few years, two other manufacturers have introduced their brands of high tensile strength stainless steel wires, which they claim to be equivalent to or superior to the Australian wires. This study was undertaken to evaluate and compare the physical properties of high tensile A.J.Wilcock (Australian) wires with the newly introduced high tensile wires and critically assess their claim for superiority. The results obtained were statistically analyzed. It was found that in 0.020" size, Wilcock Special Plus wire had greater strength and stiffness than the Ortho Organizers wire. In the 0.018" size, Wilcock Premium and Special Plus wire had greater strength and range and lesser friction and relaxation, while T. P. Premier wires had almost the same strength, but greater friction and relaxation and lesser range. In the 0.016" size, Wilcock Premium and Special Plus wire had superior stiffness, range and lesser friction and relaxation. In the 0.014" size, Wilcock Premium and Special Plus wire had greater strength and range while the Ortho Organizers wires had greater stiffness. In the 0.012" and 0.010" sizes, the Wilcock Premium Plus and Supreme wires had superior strength and stiffness than the Ortho Organizers wires.

V. Raman, S.Tamilselvi, S. Nanjundan and N. Rajendran

In dentistry, the use of metallic materials as implants or fixtures (for remediation of tooth related problems) has become a practice. Although some of the most supposedly corrosion resistant materials are only used as implant materials, there are evidences to show that metal ions are released form the implanted alloys into the physiological medium. Therefore, new alloys are being evaluated for their compatibility as dental materials. The objective of the present investigation was to study corrosion behaviour of a Ti alloy in acidic artificial saliva. potentiodynamic anodic polarisastion and open circuit potential tests were used to evaluate the corrosion behaviour of Ti-6Al-7Nb in aerated artificial saliva with pH 7.4 at 37°C. The passive range was higher for the Nb-alloy compared to the potentiodynamic test for commercially pure titanium. Electrochemical impedance spectroscopy (EIS) was carried out on specimens immersed for various time durations.

Friction and wear plays an important role in determining the performance of biomaterials. To this end, the present research is carried out to understand the tribological behavior of some important biometallic alloys, CP Titanium, Ti-6Al-4V, Ti-5Al-2.5Fe, Ti-13Nb-13Zr and Co-28Cr-6Mo under fretting contacts. The fretting experiments were carried out on candidate biometallic alloys against bearing steel at 10N normal load for 10,000 cycles with relative displacement stroke between the flat and ball set to 80 μm and the frequency 10 Hz, on a fretting (low amplitude reciprocatory tangential sliding) wear tester. The tests were performed in Hank’s balanced salt solution to assess the performance of the materials in simulated body fluid (physiological) solution. The obtained research results revealed the lowest COF of 0.3 for Ti-5Al-2.5Fe/steel couple, while for other Ti-based alloys COF was in the range of 0.46-0.50. Tribomechanical wear, as evident from the observation of abrasion and cracking, is the predominant wear mechanism.

An attempt is made to review the fundamental aspects of blood material interactions at the interface and how such concept may be useful in the development of biomedical devices such as small diameter vascular graft, artificial heart, heart valve and drug delivery systems based on micro/nanoparticles. The issues related to technology development, transfer, possible future changes and necessity of regulatory aspects would also be discussed.

Glass ionomers were introduced to the profession 25 years ago and have been shown to be a very useful adjunct to restorative dentistry. Glass ionomer cement composed of a calcium – alumino – silicate glass powder and an aqueous solution of an acrylic acid homo – or copolymer. These cements possess certain unique properties that make them useful as restorative and adhesive materials, including adhesion to tooth structure and base metals, anticariogenic properties due to release of fluoride, thermal compatibility with tooth enamel, and biocompatibility. In recent years there have been considerable changes in the formulations, properties and handling properties of the glass ionomer cements for different clinical applications. It is certain that no material is perfect, but with the current level of intensive research on glass ionomers, the deficiencies that exist seem to be eliminated or at least reduced, resulting in an ever – improving range of materials of this type.

Femoral heads of different designs were prepared with bio-grade alumina. The samples were prepared by isostatic pressing, turning and subsequent sintering for 2 hrs. at 1550^oC, 1600^oC, 1650^oC. Equivalent bar samples were prepared through identical processing steps and their flexural strength were compared to the static fracture load of the alumina based femoral head. These heads were tested for cyclic fatigue under sinusoidal and walking loads and the results are discussed in the light of their microstructure, physical and mechanical properties.

There have been considerable advances in medical sciences and biotechnology in the recent past. The human biomedical research has continued to expand. In order to achieve smooth progress of research, while preventing exploitation of human subjects, it is mandatory that every proposal on biomedical research involving human subjects be cleared by an appropriately constituted institutional ethical committee. The ethics committee is also responsible for regular monitoring of the compliance of the ethical guidelines of the approved protocols, till the same are completed. The Indian Council of Medical Research has laid down special guidelines for clinical trials of drugs and medical devices. There is a proposal for establishment of Indian Medical Devices Regulatory Authority, which will regulate the quality control and marketing of medical devices in India. Once established, the system will encourage national and international marketing of medical devices.

Human saliva consists of water, glycoproteins, enzymes, antimicrobial substances and electrolytes. From biophysical point of view, saliva is a viscoelastic fluid with distinct surface activity. Commercial artificial saliva used in salivary gland disorders should resemble normal saliva in biophysical properties. In this study we evaluated the biophysical properties of saliva and existing saliva substitutes. We compared three existing substitutes Saliveze, Xialine 1, and Xialine 2. Saliveze is based on carboxymethylcellulose and the others on xanthan gum. The choice of carbohydrate polymers is justifiable because of mucoadhesive nature. Both Saliveze, and xialine 1 are Newtonian fluids (viscosity of 5.71 cP and1.36 cP respectively) where as normal saliva is non- Newtonian (15.51 cP – 2.75 cP at shear rates 0.5 - 94.5 s-1). Similar to normal saliva Xialine 2 is shear-thinning fluid but has a lower viscosity (6.60 - 3.78 cP Vs 15.51 - 2.75 cP at shear rates 0.5 – 94.5 s-1). Shear thinning property is essential to ensure proper flow and cleansing action. The surface activity of both saliva and the substitutes has not been dealt with in the literature. Minimum surface tension of saliveze, xialine 1 and xialine 2 are 64.17, 66.15 and 64.89 mN/ m respectively where as that of natural saliva is 24.85 mN/m. Also, unlike natural saliva, none of the substitutes studied showed hysteresis in their surface tension - area isotherms. The low minimum surface tension is essential for saliva film formation on the oral mucosa. The existing substitutes fall short of required biophysical criteria and modifications are required to improve them. We need surface active, shear thinning and mucoadhesive polymer as saliva substitute, possible additions could be surfaceactive phospholipids, known to be present in saliva and/or mucin, the predominant surface-active protein of natural saliva. Consideration of the biophysical criteria could lead to future development of improved substitutes.

The passive diffusion of methotrexate across the skin is very limited. Therefore, in the present study iontophoretic method of enhancing the transdermal transport of methotrexate has been used. In our study, 0.2mA/cm2 current density has been used for permeation enhancement. This study describes the effect of physicochemical properties, like cross linking density of the hydrogel, copolymerisation, duration of electrical current and alcohol pre-treatment on the transport of methotrexate across the skin using hydrogel patches.

Gum arabic, a branched polysaccharide was oxidized using periodate to generate reactive aldehdye groups on the biopolymer. Primaquine, an 8-aminoquinoline was covalently coupled onto oxidized gum arabic via imine bond and simultaneously fabricated into microspheres of less than 2 μm in size by heat denaturation in a reverse emulsion of 1:1 light paraffin oil and toluene stabilized by sorbitan sesquioleate as the surfactant. The covalent binding of primaquine to the polysaccharide using the clinically used water-soluble form of the drug, primaquine phosphate was achieved in the presence of borate buffer of pH 11. Up to 35% of the drug could be bound to the polymer backbone depending on the concentration of the drug employed initially and the degree of oxidation of the polysaccharide. Interestingly, both the aliphatic and the hindered aromatic amino groups of primaquine were found to react with the aldehdye functions through Schiff base formation leading to crosslinking of the polysaccharide with the drug itself. In vitro release of the drug from microspheres into phosphate buffer (pH 7.4, 0.1 M) at 37ºC showed that the release of primaquine from the matrix was slow, although gradually increased with time. Maximum released was below 50% of the drug payload even after 10 days. A possible reason for the poor hydrolytic susceptibility of the Schiff linkage is suggested based on the unequal reactivity of the amino groups on primaquine and its relevance in possible therapeutic application of this polymer-drug conjugate discussed.

The use of carriers made of natural polysaccharides has arisen as a promising alternative for drug delivery. The objective of this study is to utilize the pH sensitivity of alginate and the excellent bioadhesivity of chitosan by preparing chitosan blended alginate micromatrix for oral delivery of insulin. Various blending ratios were tried and the blending ratio is optimized for optimum Insulin release pattern in simulated gastric fluid (SGF) and simulated Intestinal fluid (SIF). Insulin releases from blended matrices were compared with plain alginate microsphere and chitosan coated alginate microsphere. Applying a novel In-situ method using rat intestine the bioadhesivity of all the microsystems were performed. The optimized chitosan blended alginate micromatrix was coated with chitosan for further release control and bioadhesivity. In case of chitosan blended alginate micromatrix (1:9), further coated with chitosan, only 30% of Insulin release was seen in the first two hours in SGF. A sustained release pattern was obtained releasing up to 80% of insulin in the eighth hour in SIF.

Biphasic calcium phosphate (BCP) ceramics are based on an optimum balance of the more stable hydroxyapatite (HAp) and more soluble tricalcium phosphate (high temperature phase of HAp). This paper describes the release profiles of doxycycline, a broad-spectrum antibiotic, by BCP ceramics. The BCP granules were prepared in-situ by microwave processing and subsequent pellets were formed by conventional sintering at 1000°C. The porosity of the pellets was varied by varying the amount of flour mixed with the ceramic before sintering. The BCP granules and pellets were characterized by X-ray powder diffraction method, thermal analysis and scanning electron microscope. The release profiles were studied by UV- Visible spectroscopy and the drug release was optimised by varying the porosity and loading pH. The amount of drug absorbed by the pellet formed with 40% flour content was about 70% and this also showed maximum release compared to the other systems which were studied. 

Tissue engineering provides combinations of cells, acellular biomaterials, drugs, genes or gene products that may be designed, specified, fabricated and delivered simultaneously or sequentially as therapeutic agents. A three dimensional interconnected matrix of high porosity may be used as a scaffold for seeding cells for tissue reconstruction, repair or remodeling. This paper comprises a novel method for preparation of porous alginate scaffolds for tissue engineering of liver, cartilage, bone etc. The morphology of alginate scaffolds were investigated using SEM. The scaffolds were of high porosity with interconnected pores having pore size within the range of 20-350 micrometers. The polymers were also characterized using FTIR and DSC. Preliminary biocompatibility studies have also been performed. The scaffolds may be suitable for tissue engineering of hybrid organs and for localized drug delivery. 

With the growing need for better implant materials bioglass ceramics have aroused interest because of their ability to bond with tissues. Intrinsically low strength of the former, however, restricts their use for load bearing implant applications. Sodium bio-glass powders were prepared through sol gel route. These were calcined at 8000 C for one hour to expel moisture and residual gases. Rectangular specimens with varying amount of epoxy in sodium bio-glass were prepared by curing under pressure. The modulus of rupture was determined by three-point bend test. Samples were immersed in simulated body fluid (SBF) environment for different time intervals to study the bioactivity. Tissue like growth on the surface of the samples was studied by environmental scanning electron microscopy (ESEM), and, elemental composition present on the surface by energy dispersive x-ray analysis (EDAX). Inductively coupled plasma-atomic emission spectroscopy (ICP-AES) was carried out to observe the change in ionic concentration of simulated body fluid after removal of the samples.

Poly(vinyl chloride) (PVC) was aminated by treating the resin with a concentrated aqueous solution of ethylenediamine. The aminated PVC was then reacted with hexamethylene diisocyanate to incorporate the isocyanate group onto the polymer backbone. The isocyanated PVC was further reacted with poly(ethylene glycol) (PEG) of molecular weight 600 Da. The modified polymer was characterized using infrared spectroscopy and thermal analysis. Infrared spectra showed the incorporation of PEG onto PVC. The thermal stability of the modified polymer was found to be lowered by the incorporation of PEG. Contact angle measurements on the surface of polymer films cast from a tetrahydrofuran solution of the polymer demonstrated that the modified polymer gave rise to a significantly hydrophilic surface compared to unmodified PVC. The solid/water interfacial free energy of the modified surface was 3.9 ergs/cm2 as opposed to 19.4 ergs/cm2 for bare PVC surface. Static platelet adhesion studies using platelet rich plasma showed significantly reduced platelet adhesion on the surface of the modified polymer compared to control PVC. The study showed that bulk modification of PVC using PEG using appropriate chemistry can give rise to a polymer that possesses the anti-fouling property of PEG and such bulk modifications are less cumbersome compared to surface modifications on the finished product to impart anti-fouling properties to the PVC surface. 

Surface modification of biomaterials to improve biocompatibility and corrosion resistance without changing their bulk properties is desired for many clinical applications and has become an emerging technology in biomaterial research and industry. The present study focuses on alkali treatment of 316 LVM using sodiumhydroxide and evaluation through cyclic polarisation studies in Ringer’s solution. The alloy was treated with various concentrations of sodium hydroxide and coated electrophoretically with hydroxyapatite (HAP). The efficiency of biomimetic hydroxyapatite coating on316 LVM was tested in vitro through polarisation studies. The synthesized hydroxyapatites were characterized by Fourier transform infra-red spectroscopy (FT- IR) and X-ray diffraction studies (XRD). The results demonstrated that alkali treatment reduced its corrosion susceptibility and HAP coating on the specimen further reduced its corrosion susceptibility.

Complex / Intricate and near-net shape forming advantages of Powder Injection Moulding (PIM) has led to this process being applied to metals, ceramics as well as composites processing. In the present work, biocomposites containing bioglass ceramic Apatite Wollastonite (AW) and Polymethamethacrylate (PMMA) were processed successfully using PIM. The composites with composition varying from 10- 40% PMMA were tested for modulus of rupture (MOR). The density of these composites was in the range 1.3-1.5 g/cc. Pure titanium was also injection moulded and the process parameters such as pressure, temperature etc. were optimized.