The Experts below are selected from a list of 1101 Experts worldwide ranked by ideXlab platform
Ulrich Lohbauer - One of the best experts on this subject based on the ideXlab platform.
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mechanical and hydrolytic degradation of an Ormocer based bis gma free resin composite
Clinical Oral Investigations, 2019Co-Authors: Elena Klauer, Renan Belli, Anselm Petschelt, Ulrich LohbauerAbstract:The aim of the study was to evaluate the mechanical stability of bisphenol A-glycidyl methacrylate (Bis-GMA) and Ormocer-based resin composites before and after water absorption and to examine water saturation. Disc-shaped specimens of the Bis-GMA (Grandio SO, Voco) and the Ormocer-based (Admira Fusion, Voco) dental resin composites were produced, stored in water, and weighed after pre-determined times to measure the absorbed water. Bend bars were produced and stored for 24 h in dry conditions as well as in distilled water for 14 days or 60 days at 37 °C. The initial flexural strength (FS) under quasi-static loading and flexural fatigue strength (FFS) under cyclic loading were determined under 4-point bending. Fracture toughness (KIc) of both composites was measured using the single-edge-V-notch-beam (SEVNB) technique after the same storage conditions under 3-point bending. Within the first 14 days, storage conditions did not affect the initial FS of Grandio SO, while a significant drop in initial FS was observed for Admira Fusion after 2 weeks in water and most of the water was absorbed within this time. FFS for the Bis-GMA composite was not reduced before 2 months in water, whereas for the Ormocer®-based composite, there has been a significant decrease in strength after cyclic fatigue already at 2 weeks of water storage. KIc of Admira Fusion decreased significantly after both storage periods, while KIc of Grandio SO decreased only significantly after 2 weeks of water storage. All mechanical properties of the Bis-GMA composite were superior to those of the Ormocer®-based material, except water sorption. Water storage seems to have a much more pronounced effect on the mechanical properties of Ormocer®-based dental composites in comparison to Bis-GMA-based composites.
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tailoring of physical properties in highly filled experimental nanohybrid resin composites
Dental Materials, 2011Co-Authors: Barbara Pick, Michal Pelka, Roberto Ruggiero Braga, Renan Belli, Ulrich LohbauerAbstract:Abstract Objectives To assess the elastic modulus (EM), volumetric shrinkage (VS), and polymerization shrinkage stress (PSS) of experimental highly filled nanohybrid composites as a function of matrix composition, filler distribution, and density. Methods One regular viscosity nanohybrid composite (Grandio, VOCO, Germany) and one flowable nanohybrid composite (Grandio Flow, VOCO) were tested as references along with six highly filled experimental nanohybrid composites (four Bis-GMA-based, one UDMA-based, and one Ormocer ® -based). The experimental composites varied in filler size and density. EM values were obtained from the “three-point bending” load–displacement curve. VS was calculated with Archimedes’ buoyancy principle. PSS was determined in 1-mm thick specimens placed between two (poly)methyl methacrylate rods ( O = 6 mm) attached to an universal testing machine. Data were analyzed using oneway ANOVA, Tukey's test ( α = 0.05), and linear regression analyses. Results The flowable composite exhibited the highest VS and PSS but lowest EM. The PSS was significantly lower with Ormocer. The EM was significantly higher among experimental composites with highest filler levels. No significant differences were found between all other experimental composites regarding VS and PSS. Filler density and size did not influence EM, VS, or PSS. Significance Neither the filler configuration nor matrix composition in the investigated materials significantly influenced composite shrinkage and mechanical properties. The highest filled experimental composite seemed to increase EM by keeping VS and PSS low; however, matrix composition seemed to be the determinant factor for shrinkage and stress development. The Ormocer, with reduced PSS, deserves further investigation. Filler size and density did not influence the tested parameters.
Boris N. Chichkov - One of the best experts on this subject based on the ideXlab platform.
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Synthesis and optical properties of silver nanoparticles in Ormocer
Applied Physics A, 2012Co-Authors: Andrey L. Stepanov, Aleksandr Ovsianikov, Roman Kiyan, Vladimir I. Nuzhdin, Valery F. Valeev, Yuri N. Osin, Boris N. ChichkovAbstract:Experimental results on synthesis of metal nanoparticles in Ormocer by ion implantation are presented. Silver ions were implanted into organic/inorganic matrix at an accelerating energy of 30 keV and doses in the range of 0.25⋅10^17 to 0.75⋅10^17 ion/cm^2. The silver ions form metal nanoparticles, which demonstrate surface plasmon absorption at the wavelength of 425–580 nm. The nonlinear absorption of new composite materials is measured by Z-scan technique using 150 fs laser pulses at 780 nm wavelength. Ormocer matrix shows two-photon nonlinear absorption, whereas Ormocer with silver nanoparticles demonstrates saturated absorption. Some optical applications of these composite materials are discussed.
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Pulsed laser deposition of antimicrobial silver coating on Ormocer microneedles.
Biofabrication, 2009Co-Authors: Shaun D. Gittard, Chunming Jin, Roger J. Narayan, Aleksandr Ovsianikov, Boris N. Chichkov, Nancy A. Monteiro-riviere, Shane J. Stafslien, Bret J. ChisholmAbstract:One promising option for transdermal delivery of protein- and nucleic acid-based pharmacologic agents involves the use of microneedles. However, microneedle-generated pores may allow microorganisms to penetrate the stratum corneum layer of the epidermis and cause local or systemic infection. In this study, microneedles with antimicrobial functionality were fabricated using two-photon polymerization–micromolding and pulsed laser deposition. The antibacterial activity of the silver-coated organically modified ceramic (Ormocer®) microneedles was demonstrated using an agar diffusion assay. Human epidermal keratinocyte viability on the Ormocer® surfaces coated with silver was similar to that on uncoated Ormocer® surfaces. This study indicates that coating microneedles with silver thin films using pulsed laser deposition is a useful and novel approach for creating microneedles with antimicrobial functionality.
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Three-Dimensional Cell Growth on Structures Fabricated from Ormocer® by Two-Photon Polymerization Technique
Journal of Biomaterials Applications, 2007Co-Authors: Sabrina Schlie, Aleksandr Ovsianikov, Anaclet Ngezahayo, Tilman Fabian, Hans-albert Kolb, Heinz Haferkamp, Boris N. ChichkovAbstract:Two-photon polymerization technique was applied to generate three-dimensional (3D) scaffold-like structures using the photosensitive organic—inorganic hybrid polymer Ormocer. The structures were studied with respect to potential applications as scaffold for tissue engineering. Cell counting and comet assay, respectively, demonstrated that doubling time and DNA strand breaks of CHO cells, GFSHR-17 granulosa cells, GM-7373 endothelial cells, and SH-SY5Y neuroblastoma cells were not affected by Ormocer. Ormocer related alteration of formation of tissue specific cell-to-cell adhesions like gap junctions was ruled out by double whole-cell patch-clamp technique. Additionally, growth of cells on the vertical surfaces of 3D structures composed of Ormocer is shown.
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two photon polymerization technique for microfabrication of cad designed 3d scaffolds from commercially available photosensitive materials
Journal of Tissue Engineering and Regenerative Medicine, 2007Co-Authors: Aleksandr Ovsianikov, Sabrina Schlie, Anaclet Ngezahayo, A Haverich, Boris N. ChichkovAbstract:We report on recent advances in the fabrication of three-dimensional (3D) scaffolds for tissue engineering and regenerative medicine constructs using a two-photon polymerization technique (2PP). 2PP is a novel CAD/CAM technology allowing the fabrication of any computer-designed 3D structure from a photosensitive polymeric material. The flexibility of this technology and the ability to precisely define 3D construct geometry allows issues associated with vascularization and patient-specific tissue fabrication to be directly addressed. The fabrication of reproducible scaffold structures by 2PP is important for systematic studies of cellular processes and better understanding of in vitro tissue formation. In this study, 2PP was applied for the generation of 3D scaffold-like structures, using the photosensitive organic–inorganic hybrid polymer Ormocer® (ORganically MOdified CERamics) and epoxy-based SU8 materials. By comparing the proliferation rates of cells grown on flat material surfaces and under control conditions, it was demonstrated that Ormocer® and SU8 are not cytotoxic. Additional tests show that the DNA strand breaking of GFSHR-17 granulosa cells was not affected by the presence of Ormocer®. Furthermore, gap junction conductance measurements revealed that Ormocer® did not alter the formation of cell–cell junctions, critical for functional tissue growth. The possibilities of seeding 3D structures with cells were analysed. These studies demonstrate the great potential of 2PP technique for the manufacturing of scaffolds with controlled topology and properties. Copyright © 2008 John Wiley & Sons, Ltd.
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two photon polymerization of polymer ceramic hybrid materials for transdermal drug delivery
International Journal of Applied Ceramic Technology, 2007Co-Authors: Aleksandr Ovsianikov, Roger J. Narayan, Boris N. Chichkov, Peter Mente, Nancy A Monteiroriviere, Anand DoraiswamyAbstract:Three-dimensional microneedle devices were created by femtosecond laser two photon polymerization (2PP) of organically modified ceramic (Ormocer®) hybrid materials. Arrays of in-plane and out-of-plane hollow microneedles (microneedle length=800 μm, microneedle base diameter=150–300 μm) with various aspect ratios were fabricated. The fracture and penetration properties of the microneedle arrays were examined using compression load testing. In these studies, the microneedle arrays penetrated cadaveric porcine adipose tissue without fracture. Human epidermal keratinocyte viability on the Ormocer® surfaces polymerized using 2PP was similar to that on control surfaces. These results suggest that 2PP is able to create microneedle structures for transdermal drug delivery with a larger range of geometries than conventional microfabrication techniques.
Renan Belli - One of the best experts on this subject based on the ideXlab platform.
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mechanical and hydrolytic degradation of an Ormocer based bis gma free resin composite
Clinical Oral Investigations, 2019Co-Authors: Elena Klauer, Renan Belli, Anselm Petschelt, Ulrich LohbauerAbstract:The aim of the study was to evaluate the mechanical stability of bisphenol A-glycidyl methacrylate (Bis-GMA) and Ormocer-based resin composites before and after water absorption and to examine water saturation. Disc-shaped specimens of the Bis-GMA (Grandio SO, Voco) and the Ormocer-based (Admira Fusion, Voco) dental resin composites were produced, stored in water, and weighed after pre-determined times to measure the absorbed water. Bend bars were produced and stored for 24 h in dry conditions as well as in distilled water for 14 days or 60 days at 37 °C. The initial flexural strength (FS) under quasi-static loading and flexural fatigue strength (FFS) under cyclic loading were determined under 4-point bending. Fracture toughness (KIc) of both composites was measured using the single-edge-V-notch-beam (SEVNB) technique after the same storage conditions under 3-point bending. Within the first 14 days, storage conditions did not affect the initial FS of Grandio SO, while a significant drop in initial FS was observed for Admira Fusion after 2 weeks in water and most of the water was absorbed within this time. FFS for the Bis-GMA composite was not reduced before 2 months in water, whereas for the Ormocer®-based composite, there has been a significant decrease in strength after cyclic fatigue already at 2 weeks of water storage. KIc of Admira Fusion decreased significantly after both storage periods, while KIc of Grandio SO decreased only significantly after 2 weeks of water storage. All mechanical properties of the Bis-GMA composite were superior to those of the Ormocer®-based material, except water sorption. Water storage seems to have a much more pronounced effect on the mechanical properties of Ormocer®-based dental composites in comparison to Bis-GMA-based composites.
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tailoring of physical properties in highly filled experimental nanohybrid resin composites
Dental Materials, 2011Co-Authors: Barbara Pick, Michal Pelka, Roberto Ruggiero Braga, Renan Belli, Ulrich LohbauerAbstract:Abstract Objectives To assess the elastic modulus (EM), volumetric shrinkage (VS), and polymerization shrinkage stress (PSS) of experimental highly filled nanohybrid composites as a function of matrix composition, filler distribution, and density. Methods One regular viscosity nanohybrid composite (Grandio, VOCO, Germany) and one flowable nanohybrid composite (Grandio Flow, VOCO) were tested as references along with six highly filled experimental nanohybrid composites (four Bis-GMA-based, one UDMA-based, and one Ormocer ® -based). The experimental composites varied in filler size and density. EM values were obtained from the “three-point bending” load–displacement curve. VS was calculated with Archimedes’ buoyancy principle. PSS was determined in 1-mm thick specimens placed between two (poly)methyl methacrylate rods ( O = 6 mm) attached to an universal testing machine. Data were analyzed using oneway ANOVA, Tukey's test ( α = 0.05), and linear regression analyses. Results The flowable composite exhibited the highest VS and PSS but lowest EM. The PSS was significantly lower with Ormocer. The EM was significantly higher among experimental composites with highest filler levels. No significant differences were found between all other experimental composites regarding VS and PSS. Filler density and size did not influence EM, VS, or PSS. Significance Neither the filler configuration nor matrix composition in the investigated materials significantly influenced composite shrinkage and mechanical properties. The highest filled experimental composite seemed to increase EM by keeping VS and PSS low; however, matrix composition seemed to be the determinant factor for shrinkage and stress development. The Ormocer, with reduced PSS, deserves further investigation. Filler size and density did not influence the tested parameters.
Aleksandr Ovsianikov - One of the best experts on this subject based on the ideXlab platform.
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Three-dimensional cell growth on structures fabricated from Ormocer by two-photon polymerization technique
2016Co-Authors: Sabrina Schlie, Aleksandr Ovsianikov, Anaclet Ngezahayo, Tilman Fabian, Hans-albert Kolb, Heinz HaferkampAbstract:ABSTRACT: Two-photon polymerization technique was applied to generate three-dimensional (3D) scaffold-like structures using the photosensitive organic–inorganic hybrid polymer Ormocer. The structures were studied with respect to potential applications as scaffold for tissue engineering. Cell counting and comet assay, respectively, demonstrated that doubling time and DNA strand breaks of CHO cells, GFSHR-17 granulosa cells, GM-7373 endothelial cells, and SH-SY5Y neuroblastoma cells were not affected by Ormocer. Ormocer related alteration of formation of tissue specific cell-to-cell adhesions like gap junctions was ruled out by double whole-cell patch-clamp technique. Additionally, growth of cells on the vertical surfaces of 3D structures composed of Ormocer is shown. KEY WORDS: tissue engineering, two-photon polymerization, Ormocer, 3D scaffolds, gap junction, comet assay, DNA strand breaks
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Synthesis and optical properties of silver nanoparticles in Ormocer
Applied Physics A, 2012Co-Authors: Andrey L. Stepanov, Aleksandr Ovsianikov, Roman Kiyan, Vladimir I. Nuzhdin, Valery F. Valeev, Yuri N. Osin, Boris N. ChichkovAbstract:Experimental results on synthesis of metal nanoparticles in Ormocer by ion implantation are presented. Silver ions were implanted into organic/inorganic matrix at an accelerating energy of 30 keV and doses in the range of 0.25⋅10^17 to 0.75⋅10^17 ion/cm^2. The silver ions form metal nanoparticles, which demonstrate surface plasmon absorption at the wavelength of 425–580 nm. The nonlinear absorption of new composite materials is measured by Z-scan technique using 150 fs laser pulses at 780 nm wavelength. Ormocer matrix shows two-photon nonlinear absorption, whereas Ormocer with silver nanoparticles demonstrates saturated absorption. Some optical applications of these composite materials are discussed.
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Pulsed laser deposition of antimicrobial silver coating on Ormocer microneedles.
Biofabrication, 2009Co-Authors: Shaun D. Gittard, Chunming Jin, Roger J. Narayan, Aleksandr Ovsianikov, Boris N. Chichkov, Nancy A. Monteiro-riviere, Shane J. Stafslien, Bret J. ChisholmAbstract:One promising option for transdermal delivery of protein- and nucleic acid-based pharmacologic agents involves the use of microneedles. However, microneedle-generated pores may allow microorganisms to penetrate the stratum corneum layer of the epidermis and cause local or systemic infection. In this study, microneedles with antimicrobial functionality were fabricated using two-photon polymerization–micromolding and pulsed laser deposition. The antibacterial activity of the silver-coated organically modified ceramic (Ormocer®) microneedles was demonstrated using an agar diffusion assay. Human epidermal keratinocyte viability on the Ormocer® surfaces coated with silver was similar to that on uncoated Ormocer® surfaces. This study indicates that coating microneedles with silver thin films using pulsed laser deposition is a useful and novel approach for creating microneedles with antimicrobial functionality.
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Three-Dimensional Cell Growth on Structures Fabricated from Ormocer® by Two-Photon Polymerization Technique
Journal of Biomaterials Applications, 2007Co-Authors: Sabrina Schlie, Aleksandr Ovsianikov, Anaclet Ngezahayo, Tilman Fabian, Hans-albert Kolb, Heinz Haferkamp, Boris N. ChichkovAbstract:Two-photon polymerization technique was applied to generate three-dimensional (3D) scaffold-like structures using the photosensitive organic—inorganic hybrid polymer Ormocer. The structures were studied with respect to potential applications as scaffold for tissue engineering. Cell counting and comet assay, respectively, demonstrated that doubling time and DNA strand breaks of CHO cells, GFSHR-17 granulosa cells, GM-7373 endothelial cells, and SH-SY5Y neuroblastoma cells were not affected by Ormocer. Ormocer related alteration of formation of tissue specific cell-to-cell adhesions like gap junctions was ruled out by double whole-cell patch-clamp technique. Additionally, growth of cells on the vertical surfaces of 3D structures composed of Ormocer is shown.
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two photon polymerization technique for microfabrication of cad designed 3d scaffolds from commercially available photosensitive materials
Journal of Tissue Engineering and Regenerative Medicine, 2007Co-Authors: Aleksandr Ovsianikov, Sabrina Schlie, Anaclet Ngezahayo, A Haverich, Boris N. ChichkovAbstract:We report on recent advances in the fabrication of three-dimensional (3D) scaffolds for tissue engineering and regenerative medicine constructs using a two-photon polymerization technique (2PP). 2PP is a novel CAD/CAM technology allowing the fabrication of any computer-designed 3D structure from a photosensitive polymeric material. The flexibility of this technology and the ability to precisely define 3D construct geometry allows issues associated with vascularization and patient-specific tissue fabrication to be directly addressed. The fabrication of reproducible scaffold structures by 2PP is important for systematic studies of cellular processes and better understanding of in vitro tissue formation. In this study, 2PP was applied for the generation of 3D scaffold-like structures, using the photosensitive organic–inorganic hybrid polymer Ormocer® (ORganically MOdified CERamics) and epoxy-based SU8 materials. By comparing the proliferation rates of cells grown on flat material surfaces and under control conditions, it was demonstrated that Ormocer® and SU8 are not cytotoxic. Additional tests show that the DNA strand breaking of GFSHR-17 granulosa cells was not affected by the presence of Ormocer®. Furthermore, gap junction conductance measurements revealed that Ormocer® did not alter the formation of cell–cell junctions, critical for functional tissue growth. The possibilities of seeding 3D structures with cells were analysed. These studies demonstrate the great potential of 2PP technique for the manufacturing of scaffolds with controlled topology and properties. Copyright © 2008 John Wiley & Sons, Ltd.
Ralf Hellmann - One of the best experts on this subject based on the ideXlab platform.
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Waveguide Bragg gratings in Ormocer hybrid polymers.
Optics Express, 2016Co-Authors: Maiko Girschikofsky, M. Förthner, Lothar Frey, Mathias Rommel, Ralf HellmannAbstract:We report on the fabrication of Bragg gratings within rib-type waveguides of previously UV-cured inorganic-organic Ormocer hybrid polymers by applying the interferometric phase mask technique in conjunction with deep-UV laser radiation. The fabrication process as well as the influence of the applied laser fluence and the length of the Bragg grating on the characteristics of the Bragg grating’s transmission and reflection spectra are discussed and compared to numerical simulations and calculations. Depending on the applied laser fluence and the chosen grating length, waveguide Bragg gratings with strong reflectivities of up to 98 % and narrow bandwidths of down to 120 pm have been achieved.