Biomechanical and histological evaluation of hydrogel implants in articular cartilage

We evaluated the mechanical behavior of the repaired surfaces of defective articular cartilage in the intercondylar region of the rat femur after a hydrogel graft implant. The results were compared to those for the adjacent normal articular cartilage and for control surfaces where the defects remained empty. Hydrogel synthesized by blending poly(2-hydroxyethyl methacrylate) and poly(methyl methacrylate-co-acrylic acid) was implanted in male Wistar rats. The animals were divided into five groups with postoperative follow-up periods of 3, 5, 8, 12 and 16 weeks. Indentation tests were performed on the neoformed surfaces in the knee joint (with or without a hydrogel implant) and on adjacent articular cartilage in order to assess the mechanical properties of the newly formed surface. Kruskal-Wallis analysis indicated that the mechanical behavior of the neoformed surfaces was significantly different from that of normal cartilage. Histological analysis of the repaired defects showed that the hydrogel implant filled the defect with no signs of inflammation as it was well anchored to the surrounding tissues, resulting in a newly formed articular surface. In the case of empty control defects, osseous tissue grew inside the defects and fibrous tissue formed on the articular surface of the defects. The repaired surface of the hydrogel implant was more compliant than normal articular cartilage throughout the 16 weeks following the operation, whereas the fibrous tissue that formed postoperatively over the empty defect was stiffer than normal articular cartilage after 5 weeks. This stiffness started to decrease 16 weeks after the operation, probably due to tissue degeneration. Thus, from the biomechanical and histological point of view, the hydrogel implant improved the articular surface repair.30731

A Contribution To The Development Of A Human-machine Exoskeleton Device Using Rapid Prototyping Technology

In the present paper it is presented a finger exoskeleton able to acquire the position of the joints to be used as a guide to an avatar. The goal was to develop a cheap, reliable and comfortable device. The methods employed were CAD and Rapid Prototyping technology. © 2011 IEEE.17891794IEEE Robotics and Automation Society,Chinese University of Hong Kong,Chiba Institute of Technology,The Robio Foundation,Air Force Office of Scientific ResearchTorre, G.R.D.L., Grant, D., Cruz-Hernandez, M., Astley, O.R., Hayward, V., Haptic interfaces and devices (2004) Sensor Review, 24 (1), pp. 16-29Bergamasco, M., Antonio, F., Carlo, A.A., Exoskeletons as Man- Machine Interface Systemsfor Teleoperation and Interaction in Virtual Environments (2007) Advances in Telerobotics, STAR, 31, pp. 61-76Rosário, J.M., Princípios de Mecatrônica, , São Paulo: Prentice HallProvenza, F., (1976) Desenhista de Máquinas, , São Paulo: Escola Pro-Tec. 3°.edAhrens, C.H., Ferreira, C.V., Petrusch, G., De Carvalho, J., Santos, J.R.L., Da Silva, J.V.L., Volpato, N., (2007) Prototipagem Rápida, p. 266. , Editora Edgard BlücherSrinivasan, M.A., Basdogan, C., Haptics in Virtual Environments: Taxonomy, Research Status, and Challenges (1997) Computer and Graphics, 21 (4), pp. 393-404. , JulyMavroidis, C., DeLaurentis, K.J., Won, J., Alam, M., Fabrication of Non-Assembly Mechanisms and Robotic Systems Using Rapid Prototyping (2001) Journal of Mechanical DesignI, 123 (4), pp. 516-524Koyama, T., Yamano, I., Takemura, K., Maeno, T., Multi-fingered exoskeleton haptic device using passive force feedback for dexterous teleoperation (2002) IEEE/RSJ International Conference on Intelligent Robots and System, 3, pp. 2905-2910Iwata, H., Artificial Reality with force-feedback: Development of Desktop Virtual Space with Compact Master Manipulator (1990) Computer Graphics, 24 (4), pp. 165-170Stergiopoulos, P., Fuchs, P., Laurgeau, C., Design of a 2-Finger Hand Exoskeleton for VR Grasping Simulationm EuroHaptics 2003Bouzit, M., Burdea, G., Popescu, G., Boian, R., The Rutgers Master II - New Design Force-Feedback Glove (2002) IEEE/ASME Transactions on Mechatronics, 7 (2), pp. 256-26

Study Of The Sol-gel Processing Of Glass-ceramic Powders In The Sio2-al2o3-cao-caf2 System. I. Effect Of Powder Composition On Gel Time And Temperature

To determine the effect of powder composition on gel time and temperature, 12 sol-gel derived glasses in the SiO2-Al2O3-CaO-CaF2 system with different compositions chosen from a 21-point design generated through the mixture design technique were synthesised. Gel times varied from a few seconds at room temperature to a few hours at 75°C, as the fluoride content was increased. The longest gel times were observed for those compositions with the largest amounts of aluminium regardless of their fluoride ion concentrations. As the fluoride ion concentration was increased, the effect of both silicon and calcium concentrations on the gel times became gradually smaller. Accordingly, gel temperatures were found to vary from 75°C, for glasses with low fluoride content (3 mol% as H2SiF6), to room temperature, for those with higher fluoride contents (9 and 15 mol% as H2SiF6). Experimental data on the compositional dependence of gel time for the system studied was fitted using a quadratic model, with a square multiple correlation coefficient of 0.9962.2475057Williams, J., Billington, R., Pearson, G., (1992) Br. Dent. J., 173, p. 195McLean, J.W., (1992) Br. Dent. J., 173, p. 437McLean, J.W., (1991) Clin. Mater., 7, p. 283Brook, I.M., Craig, G.I., Lamb, D.J., (1991) Clin. Mater., 7, p. 295Lindeque, B.P., Jonck, L.M., (1993) Clin. Mater., 14, p. 49Hill, R.G., Goat, C., Wood, D., (1992) J. Am. Ceram. Soc., 75 (4), p. 778Li, R., Clark, A.E., Hench, L.L., (1991) J. Appl. Biomater., 2, p. 231Rabinovich, E.M., Kopylov, N.A., Brucem, A.J., Trevor, P.L., (1993) J. Non-Cryst. Solids, 160, p. 126James, P.F., (1995) J. Non-Cryst. Solids, 181, p. 1Jaymes, I., Douy, A., (1995) J. Sol-Gel Sci. Technol., 4, p. 7Taira, M., Yamaki, M., (1995) J. Mater. Sci. Mat. Med., 6, p. 197Cornell, J.A., (1990) Experiments with Mixtures, Designs, Models and the Analysis of Mixture Data, , Wiley, New YorkHill, R.G., Wilson, A.D., (1978) Glass Technol., 4, p. 150Wilson, A.D., McLean, J.W., (1988) Glass Ionomer Cement, , Quintessence, Chicago, ILZolotar, M.S., Zavaglia, C.A.C., Cardoso, L.P., Fraymann, J.A., (1998) Proceeding of the 11th International Symposium on Bioceramics in Medicine, , New York, USA, Bioceramics, 11 NovemberIller, R.K., (1979) The Chemistry of Silica, , Wiley, New YorkBrinker, C.J., Scherrer, G.W., (1990) Sol-Gel Science, , Academic Press, New Yor

Complex Glasses To Dental Composite

The characterization of the complex glasses, obtained by the sol-gel process and the melting of the corresponding oxides, using scanned electron microscopy was studied. The microanalyses study results indicated that the ceramic synthesized by the sol-gel process presents a homogeneous and uniform distribution of the components in the maximization interval studied. The analysis of the mechanical study results demonstrated the best mechanical behavior of the composites prepared with ceramics proceeding of the sol-gel process (SGC). It was found that the sol-gel process represent an easy, quickly and ship method to obtain different ceramic with high grade of homogeneity.975Wilson, A.D., Glass ionomer cements: Origins, development and future (1991) Clinical Materials, 7, pp. 275-282Fruits, T.J., Uses and properties of current glass ionomer cements: A review (1996) General Dentistry, SEPT-OCT, pp. 410-418Watts, D., Dental materials: 1997 literature review (1999) Journal of Dentistry, 27, pp. 401-43

Degradation Physico-mechanical Of Poly(l-lactide Acid)

The physico-mechanical properties of amorphous and crystalline rods were observed for osteosynthesis applications. Molded polylactide acids were submerged in buffer phosphate and were analyzed by Differential scanning calorimetry (DSC). Their microstructures are investigated by SEM and their bending strengths were evaluated in a MTS. The control of crystallinity has a significant effect on the degradation process and application for osteosynthesis.29

Ftir Studies On The Effect Of Network Connectivity In The Cement Forming Ability Of Sol-gel Glasses In The Sio2-al2o3-cao-caf2 System

The first studies on the cement forming ability of the glasses employed in the formulation of useful glass-ionomer cements attributed a crucial role to the Al2O3/SiO2 ratio, which was required to be higher than 1/2 by mass for cement formation. More recently, the use of the concepts such as network connectivity or crosslink density to formulate glass compositions with a good cement-forming ability has been proposed in the literature. In the present work, the effect of network connectivity on the cement-formation ability of high purity, homogeneous sol-gel glasses of different compositions in the SiO2-Al2O3-CaO-CaF2 system was qualitatively evaluated by FTIR spectroscopy. The cement-forming ability of the calcined sol-gel glasses was assessed at different powder/liquid ratios by determining their setting behaviour according to the procedure described in the ISO 9917 - Dental water-based cements. The network connectivities of the calcined sol-gel glasses were qualitatively evaluated by Fourier transform infrared (FTIR) spectroscopy. The analysis of the FTIR spectra provided useful qualitative information on the network connectivity of the sol-gel glasses, which proved to be more efficient than the Al2O3/SiO2 ratio as a way of evaluating and predicting the reactivity, and hence, the cement forming ability of these glasses.192-195749752McLean, J.W., Nicholson, J.W., Wilson, A.D., (1994) Quintessence International, 25, p. 577Wilson, A.D., McLean, J.W., (1988) Glass -Ionomer Cement, p. 2748. , Illinois Quintessence Publishing CoHill, R.G., (1996) J. Mater. Sci Letters, 15, p. 1122Darling, M., Hill, R., (1994) Journal of Dentistry, 5, p. 299Zolotar, M.S., Bavaresco, V.P., Zavaglia, C.A.C., (1999) J. Non-Cryst. Sol., 247, p. 50(1991) Dental Water-Based Cements, p. 138. , International Standard Organization,Genévre.ISO-9917Villegas, M.A., Navarro, J.M.F., (1988) J. Mater. Sci, 23, p. 2464Bansal, N.P., (1992) J. Mater. Sci, 27, p. 292

Biomechanical and histological evaluation of hydrogel implants in articular cartilage

We evaluated the mechanical behavior of the repaired surfaces of defective articular cartilage in the intercondylar region of the rat femur after a hydrogel graft implant. The results were compared to those for the adjacent normal articular cartilage and for control surfaces where the defects remained empty. Hydrogel synthesized by blending poly(2-hydroxyethyl methacrylate) and poly(methyl methacrylate-co-acrylic acid) was implanted in male Wistar rats. The animals were divided into five groups with postoperative follow-up periods of 3, 5, 8, 12 and 16 weeks. Indentation tests were performed on the neoformed surfaces in the knee joint (with or without a hydrogel implant) and on adjacent articular cartilage in order to assess the mechanical properties of the newly formed surface. Kruskal-Wallis analysis indicated that the mechanical behavior of the neoformed surfaces was significantly different from that of normal cartilage. Histological analysis of the repaired defects showed that the hydrogel implant filled the defect with no signs of inflammation as it was well anchored to the surrounding tissues, resulting in a newly formed articular surface. In the case of empty control defects, osseous tissue grew inside the defects and fibrous tissue formed on the articular surface of the defects. The repaired surface of the hydrogel implant was more compliant than normal articular cartilage throughout the 16 weeks following the operation, whereas the fibrous tissue that formed postoperatively over the empty defect was stiffer than normal articular cartilage after 5 weeks. This stiffness started to decrease 16 weeks after the operation, probably due to tissue degeneration. Thus, from the biomechanical and histological point of view, the hydrogel implant improved the articular surface repair

Synthesis Of Nanostructured Hydroxyapatite: A Comparative Study Between Sol-gel And Aqueous Solution Precipitation

Particle size is one of the most important factors to the successful application of calcium phosphate bioceramics as it may have an important role on its final properties such as mechanical resistance and reactivity. Thus, a process which results on very small and homogeneous particles is required, since it avoids further contamination derived from long milling times. On this context, a process such as sol-gel synthesis may be feasible, due to its simplicity on handling and its well known characteristic of producing homogeneous nanoparticles. Moreover, precipitated HA also may lead to satisfactory results regarding particle size and phase purity. The aim of this article was to demonstrate a preliminary characterization study of powders obtained by both methods and to compare them to a commercial sample available in Brazil. Characterization was made by XRD, Scherrer's equation, XRF, SEM-LV, SEM-FEG and SEM-EDS. It has been found out that all samples consist of pure nanostructured hydroxyapatite with crystallite size between 37nm and 62nm.396-398623626Quina, F.H., Nanotecnologia e o meio ambiente: Perspectiva e riscos. (2004) Química nova, 27 (6), pp. 1028-1029Kawachi, E.Y., Bertran, C.A., Reis, R.R., Alves, O.L., Biocerâmicas: Tendências e pespectivas de uma área interdisciplinar (2000) Química nova, 23 (4), pp. 518-522Villora, J.M., Callejas, P., Barba, M.F., Métodos de síntesis y comportamiento témico del Hidroxiapatito. (2002) Bol. Soc. Esp. Cerám. Vidrio, 41 (5), pp. 443-450Feng, W., Mu-sen, L., Yu-peng, L., Yong-xin, Q., (2005) Materials Letters, 59, pp. 916-919Rigo, E.C.S., (1995) Efeito das condições de precipitaç ão sobre as características físico-químicas da hidroxipatita, , MSc Dissertation, Universidade Federal de São Carlos, UFSCAR, BrasilSouza, E.A., Duque, J.G.S., Kubota, L., Meneses, C.T., (2007) Journal of Physics and Chemistry of Solids, 68 (4), pp. 594-59