Department of Chemical and Biochemical Engineering
Chair of the Division of Biomaterials Science
Faculty of Medicine and Dentistry
B.Sc. (Cairo Egypt) 1974
M.Eng. (McGill) 1977
Ph.D. (Halifax, NS) 1987
Dr. RIZKALLA’s main area of research is in wet chemical synthesis and physical and mechanical characterization of glasses and ceramic biomaterials that are used for dental and orthopaedic applications.
Ceramic Fillers for Dental Composites: Ceramic filler particles were synthesized by so-gel chemistry. These fillers exhibit unique shapes and provide mechanical interlocking with the resin matrix., resulting in a significant increase in the elastic moduli and fracture toughness of dental composites.
Castable Glass-Ceramics: Castable glass ceramics were synthesized by sol-gel chemical techniques. These materials provide superior mechanical properties over conventional castable glass-ceramics. These glasses have great potential use for all ceramic dental crowns.
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 glass formulations was determined by differential thermal analysis (DTA). DTA is a valuable technique for the optimization of heat treatment that leads to superior properties of biomedical glass-ceramics.
Ion 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.
Bioactive Glass-Ceramics: 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 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 is being conducted for scaffolds.
KEYWORDS: Biomaterials, synthesis, bioactive glass-ceramic, dental, crystallization, cement, composite, sol-gel, mechanical, physical, chemical, coating, scaffold