Rizkalla, Amin - University of Western Ontario - Department of Chemical and Biochemical Engineering

研究领域

Dr. Rizkalla’s main area of research is in wet chemical synthesis and physical and mechanical and biological characterization of glasses, ceramic, nanocomposite and hybrid biomaterials that are used for dental and orthopaedic applications. Nano-Ceramic Fillers for Composite Biomaterials Functionalized nano-ceramic particles, fibers and nanotubes are being synthesized by so-gel chemistry, hydrothermal and electrospinning processes. These nanofillers exhibit unique shapes and provide mechanical interlocking with the resin matrix. These modifications result in a significant increase in the elastic moduli and fracture toughness of dental composites. Additional work is being conducted in the synthesis and characterization of nano-composites. Synthesis of High Strength Machinable Glass-Ceramics for the CEREC System Wet chemical synthesis provides glass-ceramics of controlled chemistries and improved strength, modulus of elasticity and fracture toughness. A wide range of glass formulations in the system K2O-Na2O-CaO-F-A2O3-SiO2-X are being synthesized by wet chemical methods where X is a network modifier such as TiO2, ZrO2, La2O3, CeO2, and Y2O3. Synthesized powders are processed using novel sol-gel chemistry. From DTA exotherms of resultant glasses, kinetics of crystallization is studied. Optimum heating schedule for each glass will depend upon chemical composition. Effect of structure and composition on mechanical and wear properties of glass-ceramics are studied and compared with Commercial CEREC systems. Kinetics of Crystallization of Synthesized Glasses The control of the heating schedule, nucleation and crystallization of glasses is important to optimize the physical chemical and mechanical properties of these materials. The kinetics of crystallization of ion leachable and bioactive and castable glass formulations was determined by differential thermal analysis (DTA). We have demonstrated that DTA is a valuable technique for the optimization of heat treatment that leads to superior properties of biomedical glass-ceramics. on Leachable Glasses We have developed ion leachable glasses that contain a high percentage fluoride. When these glasses were reacted with poly (acrylic acid), experimental glass-ionomer cements were obtained. These cements exhibited superior mechanical properties & fluoride release that was significantly higher than any commercial material available on the market. The main advantage of high fluoride release is the reduction of secondary caries and stimulation of bone growth. Bioactive Glass-Ceramics-Polymer Composites We have conducted preliminary research dealing with the synthesis and characterization of bioactive glasses and glass-ceramic-polymer composites. We found that the ionic release of calcium and phosphorus from the glass is dictated by the concentration of non-bridging oxygen within the glass materials. We also found that the silane treatment can produce a barrier to ionic release. In contrast to conventional methacrylate bone cement, the range of dynamic elastic moduli values for the experimental composite systems were significantly higher and within the typical range of values for cortical bone. This finding has the potential of reducing stress-shielding effect between the implant and bone. More research is being developed in the area of thin film coating of hydroxyapatite and bioactive glasses onto metal substrates and high strength bioceramics to be used for dental and orthopaedic implants. Additional work on the synthesis of porous bioceramics, biodegradable polymers and biocomposites is being conducted for scaffolds used for dental and orthopaedic applications. Other research interest is in micro-encapsulation and controlled release of bio-effectors as well as immobilization of proteins for promotion of mineralization.

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Santos, M. J. M. C., Driessen, C.H., De Freitas, A. P., Rizkalla, A. S. and Santos Jr., G. C., (2012) “In Vitro Shear Bond Strength of Resin-Based Luting Cements to Dentin.” General Dentistry, 60 (4) 215-20. Sprinath, D., Shigang, L., Rizkalla, A. S., Mequanint, K., (2012), “Fibrous Biodegradable L- Alanine Based Scaffold for Vascular Tissue Engineering.” Accepted for publication in Tissue Engineering and Regenerative Medicine. Allo, B. A., Costa, D. O., Dixon, S. J., Mequanint, K. And Rizkalla, A. S., (2012) “Bioactive and Biodegradable Nanocomposites and Hybrid Biomaterials for Bone Regeneration.” J. Funct. Biomater., 3, 432-462. Costa, D.O., Dixon, S. J. and Rizkalla, A. S., (2012) “One-and Three Dimensional Growth of Hydroxyapatite Nanowires during Sol-Gel Hydrothermal Synthesis.” ACS Applied Materials and Interfaces, 4, 1490-99. Costa, D.O., Allo, B.A., Klassen, R., Hutter, J.L., Dixon, S.J. and Rizkalla, A.S., (2012) “Synthesis and Characterization of Novel Biomimetic Calcium Phosphate Coatings with Controlled Surface Topographies”. In Press Langmuir. Bapoo, H., Rizkalla, A.S., Santos, M.J. (2011) “Effect of Dedntin Cleaning Techniques on the Shear Bond Strength of Self Adhesive Resin”. In Pres Operative Dentistry. Nong, Z., O’Neil, C., Lei, M., Gros, R., Rizkalla, A. S., Mequanint, K., Li, S., Frontini, M. J., Fang, O. and Pichering, J. G. (2011) “Type I Collagen Cleavage is Essential for Effective Fibrotic Repair Following Myocardial Infarction”. Am. J. of Pathology, In Press. Passos, S. P., Santos, M.J.C.M., El Mowafi, O., Rizkalla, A. S. and Santos Jr, G.C. (2011) Diametral Tensile Strength of Composite Core Materials with Cured and Uncured Fiber Posts”. General Dentistry, 59, (2), 125-28. Dreissen, C. H., Santos, Jr, G. C. and Rizkalla, A. S. (2011) “Diametral Tensile Strength of Four Composite Resin Core Materials with and without Centered Fiber Dowels”. General Dentistry, In Press. Santos, M.J.C.M., Driessen, C.H., Freitas, A.P., Rizkalla, A.S. and Santos Jr, G.C. (2011) “In Vitro Sgear Bond Strength of Resi-Based Luting Cements to Dentin”. General Dentistry, In Press. Sui, R., Rizkalla, A. S. and Charpentier, P. A., “Experimental Study on the Morphology and Porosity of TiO2 Aerogels synthesized in Supercritical Carbon Dioxide”. Accepted for publication in Microporous and Mesoporous Materials, January, 2011 Dreissen, C. H., Ji, D. Y-J, Rizkalla, A. S. and Santos Jr, G. C., (2011) “Diametral Tensile Strength of Core Composite Material with Cured and Uncured Fiber Posts”. General Dentistry, Nov/Dec, 219-223. Mohammadi, H., Bahramian, H. and Rizkalla, A. S., (2010) “A Numerical Technique to Evaluate Flexural Stiffness of Long Bones Affected by Cracks and Porosities”. Journal of Mechanics in Medicine and Biology, 0(1), 1-39. Allo, B. A., Rizkalla, A. S. and Mequanint, K., (2010) “Synthesis and Electrospinning of e-Polycaprolactone-Bioactive Glass Hybrid via Sol-Gel Process, Langmuir, 26(23), 18340-18348. Passos, S.P., Santos, MJMC, El Mowafy, O., Rizkalla, A. S. and Santos Jr, G. C., “Diametral Tensile Strength of Composite Core Materials of Cured and Uncured Fiber Posts”. Accepted for publication in General Dentistry, June, 2010. Karimi, P., Rizkalla, A. S. and Mequanint, K. (2010) “Versatile Biodegradable Poly (Ester Amide)s Derived from a-Amino Acids for Vascular Tissue Engineering”. Materials, 3, 2346-2368. Khaled, S. M. Z., Charpentier, P. A. and Rizkalla, A. S. (2010)“Synthesis and Characterization of PMMA Based Experimental Bone Cements Reinforced with TiO2-SrO Nanotubes” Acta Biomaterialia,6(8), 3178-3186. Khaled, S. M. S., Charpentier, P. A. and Rizkalla, A. S. (2010) “Physical and Mechanical Properties of PMMA Bone Cement Reinforced with Nano-Sized Titania Fibers” J. of Biomaterials Application. Published on line before print Mar 5, 2010, doi: 10.1177/0885328209356944. Chan, W. D., Goldberg, H. A., Hunter, G. K., S. J. Dixon and Rizkalla, A. S., (2010) Modification of Polymer Networks with Bone Sialoprotein Promotes Cell Attachment and Spreading“, J. Biomed.Mater. Res. Part A 94A, 945-952 Khaled, S. M. Z., Miron, R. J., Hamilton, D. W., Charpentier, P. A., and Rizkalla, A. S., (2009) “Reinforcement of Resin Based Cement with Titania Nanotubes”, Dent. Mater. 26 (2), pp. 169-178. Chan, W. D., Perinpanayagam, H., Goldberg, H. A., Hunter, G. K., Dixon, S. J. and Rizkalla, A. S., (2009) “Tissue Engineering Scaffolds for the regeneration of Craniofacial Bone” J. Can. Dent. Assoc. 75 (5), pp. 373-377. Santos, Jr., G. C., Santos, M. J. M. C., and Rizkalla, A. S., (2009) “Adhesive Cementation of Etchable Ceramic Esthetic Restorations” J. Can. Dent. Assoc. 75 (5), pp. 379-384. Sui, R., Rizkalla, A. S., Charpentier, P. A., (2008) “Kinetics Study on the Sol-Gel Reactions in Supercritical CO2 by using in situ ATR-FTIR Spectroscopy: Crystal Growth and Design 8 (8), pp. 3024-3031 Alibeik, S., Sheardown, H., Rizkalla, A. S. and Mequanint, K., (2007) “Protein Adsorption and Platelet Adhesion onto Ion-Containing Polyurethanes”. ”Journal of Biomaterials Science: Polymer Edition 18 (9), pp. 1195-1210. Alibeik, S., Rizkalla, A. S. and Mequanint, K., (2007) “The Effect of Thiolation on the Mechanical and Protein Adsorption Properties of Polyurethanes.” European Polymer Journal 43 (4), pp. 1415-1427.