Browsing by Author "Varma, H"

Now showing 1 - 17 of 17
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    Combined Treatment Effects Using Bioactive-Coated Implants and Ceramic Granulate in a Rabbit Femoral Condyle Model
    (CLINICAL IMPLANT DENTISTRY AND RELATED RESEARCH, 2016) Preethanath, RS; Rajesh, P; Varma, H; Anil, S; Jansen, JA; van den Beucken, JJJP
    Background: Resolution of peri-implant defects resulting from implant placement in the freshly extracted site demands for a bone graft substitute that stimulates bone regeneration and hence facilitates implant integration. In view of this, the addition of silica to hydroxyapatite (HASi) could enhance the bioactive behavior of ceramic materials and implant surfaces coated with bioactive ceramics might benefit the interaction between bone and implant. Purpose: To evaluate the bone response to implants coated with hydroxyapatite-silica (HASi) or hydroxyapatite (HA) and either or not combined with HASi and HA ceramic bone substitute particles, respectively, on bone-to-implant contact (BIC) and bone formation using a rabbit femoral condyle implant model with a gap design. Material and Methods: A total of 32 custom-made, titanium implants (Ti: diameter 5 mm, length 8 mm) with two-sided gaps were fabricated and coated with either HASi or HA using pulsed laser deposition (PLD). The implants were installed bilaterally in the femoral condyles of 16 New Zealand white rabbits. According to a randomization protocol, one gap of HASi-coated and HA-coated implants was filled with HASi particles and HA particles, respectively, and the other gap was left empty. After an implantation period of 8 weeks, the retrieved specimens were analyzed via histology and histomorphometry (i.e., bone to implant contact [BIC] and bone volume [BV]). Results: The BIC and BV around the implants were analysed for HASi-and HA-coated implants with and without the use of HASi and HA bone substitute material. Comparison of HASi-and HA-coated implants showed similar BIC for HASi( 55.7 + 11.0) and HA-coated implants (50.3 + 19.7). When coated implants were combined with bone substitute materials, HASi-coated and particle-filled implants showed higher BIC (64.3 +/- 6.8%) compared with HA-coated and HA-filled implants (54.5 +/- 10.9%). Similarly, the BV within the region of interest showed significantly higher values for the HASi-coated and HASi-filled implants (21.1 +/- 1.7%) compared with HA-coated and HA-filled implants (12.8 +/- 4.9%). Conclusions and Clinical Implications: Within the limitations of this study, it can be concluded that silicon substitution in HA favors bone regeneration compared with HA, especially when used as bone substitute material. Further studies using different healing periods will elucidate the resorption pattern of HASi granules in comparison with HA.
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    Combined Treatment Effects Using Bioactive-Coated Implants and Ceramic Granulate in a Rabbit Femoral Condyle Model.
    (Clinical Implant Dentistry and Related Research, 2015-06) Reghunathan, SP; Rajesh, P; Varma, H; Sukumaran, AS; Jansen, JA; Beucken, JJP
    Background: Resolution of peri-implant defects resulting from implant placement in the freshly extracted site demands for a bone graft substitute that stimulates bone regeneration and hence facilitates implant integration. In view of this, the addition of silica to hydroxyapatite (HASi) could enhance the bioactive behavior of ceramic materials and implant surfaces coated with bioactive ceramics might benefit the interaction between bone and implant. Purpose: To evaluate the bone response to implants coated with hydroxyapatite-silica (HASi) or hydroxyapatite (HA) and either or not combined with HASi and HA ceramic bone substitute particles, respectively, on bone-to-implant contact (BIC) and bone formation using a rabbit femoral condyle implant model with a gap design. Material and Methods: A total of 32 custom-made, titanium implants (Ti: diameter 5 mm, length 8 mm) with two-sided gaps were fabricated and coated with either HASi or HA using pulsed laser deposition (PLD). The implants were installed bilaterally in the femoral condyles of 16 New Zealand white rabbits. According to a randomization protocol, one gap of HASi-coated and HA-coated implants was filled with HASi particles and HA particles, respectively, and the other gap was left empty. After an implantation period of 8 weeks, the retrieved specimens were analyzed via histology and histomorphometry (i.e., bone to implant contact [BIC] and bone volume [BV]). Results: The BIC and BV around the implants were analysed for HASi- and HA-coated implants with and without the use of HASi and HA bone substitute material. Comparison of HASi- and HA-coated implants showed similar BIC for HASi- (55.7 + 11.0) and HA-coated implants (50.3 + 19.7).When coated implants were combined with bone substitute materials, HASi-coated and particle-filled implants showed higher BIC (64.3 1 6.8%) compared with HA-coated and HA-filled implants (54.5 1 10.9%). Similarly, the BV within the region of interest showed significantly higher values for the HASicoated and HASi-filled implants (21.1 1 1.7%) compared with HA-coated and HA-filled implants (12.8 1 4.9%). Conclusions and Clinical Implications: Within the limitations of this study, it can be concluded that silicon substitution in HA favors bone regeneration compared with HA, especially when used as bone substitute material. Further studies using different healing periods will elucidate the resorption pattern of HASi granules in comparison with HA.
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    Development of an injectable bioactive bone filler cement with hydrogen orthophosphate incorporated calcium sulfate
    (J Mater Sci Mater Med., 2015-03) Sony, S; Suresh Babu, S; Nishad, KV; Varma, H; Komath, M
    Calcium sulfate cement (CSC) has emerged as a potential bone filler material mainly because of the possibility of incorporating therapeutic agents. Delivery of the cement through a needle or cannula will make it more useful in clinical applications. However, it was not possible to make CSC injectable because of the inherent lack of viscosity. The present work demonstrates the design development of a viscous and fully-injectable CSC by incorporating hydrogen orthophosphate ions, which does not hamper the biocompatibility of the material. The effect of addition of hydrogen orthophosphate on the rheological properties of the CSC paste was studied using a custom made capillary rheometer. The physicochemical changes associated with cement setting process were examined using X-ray diffraction and Fourier transform infrared spectroscopy and the thermal changes were measured through isothermal differential scanning calorimetry. Micromorphological features of different compositions were observed in environmental scanning electron microscopy and the presence of phosphate ions was identified with energy dispersive X-ray spectroscopic analysis and inductively coupled plasma–optical emission spectroscopy. The results indicated that HPO4 2− ions have profound effects on the rheological properties and setting of the CSC paste. Significant finding is that the HPO4 2− ions are getting substituted in the calcium sulfate dihydrate crystals during setting. The variations of setting time and compressive strength of the cement with the additive concentration were investigated. An optimum concentration of 2.5 % w/w gave a fully-injectable cement with clinically relevant setting time (below 20 min) and compressive strength (12 MPa). It was possible to inject the optimised cement paste from a syringe through an 18-gauge needle with thumb pressure. This cement will be useful both as bone filler and as a local drug delivery medium and it allows minimally invasive bone defect management.
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    Effect of Surface Functionalization on the Physicomechanical Properties of a Novel Biofunctional Copolymer
    (JOURNAL OF APPLIED POLYMER SCIENCE, 2011) Sailaja, GS; Ramesh, P; Varma, H
    The physicomechanical properties of functionally active poly(hydroxyethyl methacrylate-co-methyl methacrylate) [poly(HEMA-co-MMA)] are evaluated. It has been reported that the surface phosphorylated poly(HEMA-co-MMA) is capable of eliciting direct bone bonding when implanted in vivo. Hence, it is important to examine the physicomechanical property of the copolymer as a function of surface modification. The properties assessed are differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), equilibrium swelling, compressive strength, and dynamic mechanical analysis. According to the DSC data, the glass transition temperature, T-g of poly(HEMA-co-MMA) is not significantly altered by surface phosphorylation. The TGA results demonstrated that unmodified and surface phosphorylated copolymers have similar degradation profile. The differential thermal analysis further supports the data. The equilibrium swelling of functionalized poly(HEMA-co-MMA) in phosphate buffer saline ascertained that surface phosphorylation significantly increased the hydrophilicity of the copolymer. The study further illustrated that the percentage of equilibrium swelling appreciably increases with increase in HEMA content in the copolymer and reached a plateau after 100 h. Both compressive strength and compressive modulus of poly (HEMA-co-MMA) decreased due to surface phosphorylation while dynamic storage modulus value was not altered. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 3509-3515, 2011
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    Electrospun PVA-PCL-HAB scaffold for Craniofacial Bone Regeneration
    (TISSUE ENGINEERING PART A, 2015) Prabha, RD; Kraft, DC; Melsen, B; Varma, H; Nair, PD; Kjems, J; Kassem, M
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    High surface area sol-gel nano silica as a novel drug carrier substrate for sustained drug release
    (MATERIALS RESEARCH BULLETIN, 2012) Nampi, PP; Mohan, VS; Sinha, AK; Varma, H
    Among various carrier materials for drug delivery, silica has been found to be significant for loading and sustained release of the drug. In the present study, the antibiotic gentamicin was incorporated in various amounts on to a silica matrix, using a sol-gel subcritical drying route. Crack free silica rods with a length of 1-1.5 cm, diameter of 0.5 cm and density of 1.35 g/cm(3) incorporated with gentamicin were obtained. The incorporation of gentamicin into the silica matrix was revealed by FTIR. The adsorption-desorption isotherms and pore size distribution were studied in detail. The drug elution patterns were analysed and show a biphasic mode of release. After the initial burst release, a constant release pattern is observed. A release value above the minimum inhibitory concentration (MIC) is always maintained. The amount of drug released is higher than that of many other bioactive ceramic materials. An attempt has been made to correlate the functional properties with the porosity features. (C) 2012 Elsevier Ltd. All rights reserved.
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    Hydroxyapatite scaffolds constituting highly oriented crystals derived from synthetic precursors by hydrothermal reactions
    (CERAMICS INTERNATIONAL, 2016) Mohan, N; Palangadan, R; Varma, H
    A series of hydroxyapatite scaffolds having oriented crystal morphologies were fabricated through hydrothermal exchange reactions of tri calcium phosphate porous precursors in different solutions by the regulation of reaction parameters. The newly developed scaffolds have unique crystal morphologies and a preferred orientation with hybrid micro and nano dimensional structures such as fibres, rods, tubes and flowers. These crystals of apatite grow in the a(b)-plane of the hydroxyapatite lattice with orientation along the c-axis. The developed scaffolds were subjected to in vitro bioactivity evaluation in simulated body fluid (SBF). Physicochemical characterisation of the materials were performed by scanning electron microscopy, X-ray diffraction and fourier transform infra-red spectroscopy. This study shows the transformation of a lower calcium phosphate material to a fast resorbing hydroxyapatite scaffold with a preferred orientation along the c-axis and a higher aspect ratio of crystals which is intended for use in the field of dentistry and orthopaedics as a scaffold for tissue regeneration. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
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    In vitro characterisation of bone cell activity on triphasic ceramic composites from calcium silicate-tricalciumphosphate and hydroxyapatite
    (Journal of Clinical Rehabilitative Tissue Engineering Research., 2009) Bernhardt, A; Lode, A; Babu, SS; Vogel, A; Hanke, T; Thieme, S; Varma, H; Angela, R; Sen-Wolff; Gelinsky, M; John, A
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    Microwave sintering of nanosized hydroxyapatite powder compacts
    (MATERIALS LETTERS, 2002) Vijayan, S; Varma, H
    Gel cast sample of nanocrystalline hydroxy apatite powder has been sintered to high densities by short-time microwave processing and is characterised by X-ray diffractornetry (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SCM), density measurements and Vickers microhardness (Hv) measurements. The basic crystallite size of the precipitated HAP was found to be around 35 mn by XRD and TEM studies. The gel cast samples of the above powder could be sintered to above 95% by exposing to microwave radiation for a period of 5 min. The sintered grainsize of the sample was 200 300 mn having microhardness in the range of 5.25 GPa and the effect of microwave exposure time on the densification and grainsize is reported. (C) 2002 Elsevier Science B.V. All rights reserved.
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    Novel nanoporous bioceramic spheres for drug delivery application: A preliminary in vitro investigation
    (Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology., 2013-05) Simon, D; Manuel, S; Varma, H
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    Osteogenesis of a Bioactive Ceramic-Calcium Phosphosilicate Composite System in Goat Femur Defect
    (INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, 2011) John, A; Mani, S; Gopalakrishnan, S; Babu, S; Lal, AV; Varma, H
    In spite of the array of synthetic bone grafts available, the pursuit for an ideal graft continues. In view of this, a synthetic bioactive calcium phosphosilicate composite (HABGS) has been developed combining the properties of hydroxyapatite and silicate system. The in vivo performance of HABGS granules in goat femur defect stimulated a favorable environment for de novo bone formation with faster resorption. The ceramic composite is attractive for its low Si content together with its negligible levels at implanted sites and vital organs postimplantation. Herein, we propose the safety and efficacy of this composite as a promising bone substitute.
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    Preparation of hydroxyapatite porous scaffolds from a coral like synthetic inorganic precusrsor for use as a bone graft substitute and a drug delivery vehicle
    (Materials Science and Engineering C, 2018-11) Nimi, N; Palangadan, R; Fernandez, FB; Varma, H
    A novel surfactant free hydrothermal method was developed for the preparation of large hydroxyapatite scaffolds. Synthetic calcium carbonate (calcite) was used as the starting material which when mixed with an inorganic setting solution containing phosphoric acid and sodium hydroxide forms the porous precursor body with pore size 20-700 μm. The porous precursor body was then hydrothermally converted to hydroxyapatite scaffolds when treated in basic phosphate solution of pH 10.5 at 150 °C and 15 bar pressure maintaining the structural stability and integrity. X-ray diffraction and the Fourier transform infrared spectroscopy confirmed that the developed material consist of single phase crystalline hydroxyapatite. Surface morphology and microstructures were studied using scanning electron microscopy and porosity was evaluated by micro CT analysis. The cell material interactions evaluated by cell viability assays and live cell staining methods confirmed the cell compatibility. The drug release study at physiological pH implied that the developed materials could be promising in sustained long-term release. The results emerged have shown that the hydrothermal conversion of inorganic coral-like precursor is effective to produce porous bioactive hydroxyapatite scaffolds for bone regeneration as well as drug delivery vehicles for the treatment of infectious bone diseases such as osteomyelitis.
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    Pulsed laser deposition and in vitro characteristics of triphasic - HASi composition on titanium
    (JOURNAL OF BIOMATERIALS APPLICATIONS, 2014) Palangadan, R; Sukumaran, A; Fernandez, FB; John, A; Varma, H
    Pulsed laser deposition was used to deposit bioactive triphasic glass-ceramic composition (HASi) over titanium substrate using dense HASi target. Bioactive glass compositions are considered the most useful synthetic materials for immediate bone attachment because of its bioresorption, osteoconduction and osteointegration characteristics under invivo conditions. The disadvantage of its brittleness associated with bioactive glass-ceramics has prompted its coating over metallic implants for the combination of duo mechanical and bioactive properties. The hard HASi target was able to undergo laser ablation under ambient gas pressure without bulk erosion of the target. Laser deposition was found to be efficient in depositing triphasic composition for immediate bone integration. The target and deposits were analyzed for the phase, composition and microstructural characteristics by means of X-ray diffraction, Fourier transform infrared spectroscopy, energy-dispersive X-ray analysis and scanning electron microscopy. Simultaneously, the adherent nature and mechanical behaviour of deposits were confirmed by scratch test and micro-indentation methods. Further, the invitro dissolution and bioactivity were assessed by soaking in simulated body fluid followed by elemental analysis using inductively coupled plasma spectroscopy. The deposits were found to be cell-friendly, which was indicated by the phenomenology of stem cells under invitro conditions.
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    Pulsed laser deposition and in vitro characteristics of triphasic ? HASi composition on titanium
    (Journal of Biomaterials Applications., 2014-02) Palangadan, R; Sukumaran, A; Fernandez, FB; John, A; Varma, H
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    Sodium yttrium fluoride based upconversion nano phosphors for biosensing
    (6TH INTERNATIONAL CONFERENCE ON OPTICAL, OPTOELECTRONIC AND PHOTONIC MATERIALS AND APPLICATIONS (ICOOPMA) 2014, 2015) Nampi, PP; Varma, H; Biju, PR; Kakkar, T; Jose, G; Saha, S; Millner, P
    In the present study, NaYF4-Yb3+/Er3+ having the composition NaYF4-18%Yb3+/2%Er3+ and NaYF4-20%Yb3+/2%Er3+ with and without the addition of PVP (polyvinyl pyrolidone) have been synthesised by a solution method using NaF, yttrium nitrate, ytterbium nitrate and erbium nitrate as precursors. Upconversion spectra of prepared nanomaterial under 980 nm laser excitation have been studied. The variation in upconversion spectra with new born calf serum and myoglobin has been studied. Myoglobin (Mb) may be helpful when used in conjunction with other cardiac markers for rapid determination of acute myocardial ischemia, especially in patients with a typical chest pain or nonspecific ECG changes. The variation of UC fluorescence with addition of Mb indicates the suitability of using NaYF4 based UC nanoparticles in cardiac marker detection. The detailed study is currently under progress.
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    Synthesis and Characterization of Iron Oxide Embedded Hydroxyapatite Bioceramics
    (JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 2012) Ansar, EB; Ajeesh, M; Yokogawa, Y; Wunderlich, W; Varma, H
    A homogeneous dispersion of nano iron oxide (IO) crystallites inside the hydroxyapatite (HA) particles was achieved by a co-precipitation method. This highly stable colloidal dispersion of magnetic nano composite (HAIO) was made without the use of any surfactants. The in situ generated dispersion of the composite powders showed submicron HA particles with 5 nm iron oxide inside. The phase analysis results showed the presence of hydroxyapatite (HA) and iron oxide with no tertiary phase. The enhancement of relative peak intensities with increased percentage of iron oxide phase in X-ray diffraction analysis suggests the formation of iron oxide together with HA without affecting the phase purity of the latter, which is important when the biological behavior of HA is concerned. This also confirms the quantitative nature of the precipitated nanocomposites. The High Resolution Transmission Electron Microscope (HRTEM) of the composite shows elongated crystal flakes or platelike surfaces of HA crystallites having particle sizes in the range 70-100 nm. HRTEM with XRD analysis matches HAIO only with iron oxide particles of Magnetite (Fe3O4) and HA phases. The FTIR data confirm that the introduction of iron oxide did not produce any considerable change in the chemical structure of HA.
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    Transparent hydroxyapatite ceramics through gelcasting and low-temperature sintering
    (JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 2002) Varma, H; Vijayan, SP; Babu, SS
    Transparent hydroxyapatite (HAP) was prepared by sintering gel-cast powder compacts at 1000degreesC for 2 h; the resultant HAP material was studied using X-ray diffractometry, transmission electron microscopy, scanning electron microscopy, and microhardness measurement. Nanoscale HAP crystallites were prepared using a precipitation method that involved calcium nitrate and ammonium dihydrogen orthophosphate solutions; the preparation was conducted at a temperature of 0degreesC. The precipitate was gel-cast and sintered at 1000degreesC in the form of a transparent ceramic that had a uniform grain size of 250 mum. The maximum Vickers microhardness obtained for a sample sintered at 1000degreesC was 6.57 GPa. The sintering behavior of gel-cast samples prepared from high-temperature-precipitated HAP was compared with that of material prepared at 0degreesC.