Carmem Pfeifer, DDS, PhD. Dr. Carmem Pfeifer is a Associate Professor in the Department of Restorative Dentistry, Division of Biomaterials and Biomechanics at OHSU School of Dentistry. Dr. Pfeifer teaches Dental Materials and serves as an instructor in several Restorative Dentistry pre-clinical disciplines. She also serves as advisor to graduate theses in the School of Dentistry, Department of Pediatric Dentistry. Dr. Pfeifer obtained her DDS (2001) and PhD (2007) from the University of São Paulo, Brazil. She was a post-doc fellow (2008-2011) at the University of Colorado (Aurora/Boulder). Dr. Pfeifer has published over 60 research articles in the field of Dental Materials Sciences and Polymer Chemistry and serves as the reviewer for several journals in polymer science and biomaterials, as well as for the National Institute of Dental and Craniofacial Research at NIH. Her research focuses on the development of innovative polymeric materials for restorative dentistry, as well as on the development of analytical tools to characterize polymer properties evolution in real-time. Recently, she has received the inventor of the year award from OHSU. Her research and career development has been successfully funded by the Oregon Medical Research Foundation, National Science Foundation and National Institutes of Dental and Craniofacial Research.
Department of Restorative Dentistry, Division of Biomaterials and Biomechanics at OHSU School of Dentistry
The increasing demand for esthetic dental restorations, both by patients and dentists, has stimulated the improvement of resin composites. Currently these materials are used in the vast majority of direct, chair-side restorations delivered each year. However, hydrolysis and enzymatic attack, together with polymerization shrinkage, pose a challenge to the bonded interface between the tooth and the restorative material, which reduces the life-time and reliability of the restorations. Recently, several researchers have proposed to synthesize novel monomer systems, based on tertiary methacrylamides, copper catalyzed azide-alkyne reactions, vinyl sulfones, epoxy-methacrylate hybrids and coavalent adaptable networks to be used as the organic matrix of dental composites and adhesives, completely departing from the conventional methacrylate chemistry used by nearly all current materials. The main challenge of new monomers is to resist hydrolysis and enzymatic attack, while being able to be polymerized in situ on command using the same photoactivation protocols already in place, thus facilitating its acceptance by dentists. In addition, various types of oligomeric additives (thiourethanes, nanogels and other low profile additives) are being designed to be incorporated into the resin matrix to harness advantages such as the production of more homogeneous networks with enhanced toughness, as well as enhanced depth of cure due to improved refractive index match with the inorganic fillers. In our laboratory, the results with thiol-functionalized thio-urethane oligomers in methacrylate matrices have shown significant reduction in polymerization stress accompanied by increase in conversion and fracture toughness. The materials are biocompatible and easily incorporated into commercial formulations, as already demonstrated for dual-cure cements (Bacchi, 2014, JDR). Results for highly filled composites have shown the same trend of decreased stress with similar conversions compared to the control and significantly improved mechanical properties. While reducing polymerization shrinkage and stress and improving mechanical properties are very important milestones, the main goal of composite development for the future is to substantially reduce the organic matrix degradation in the oral environment, as well as reduce the biofilm re-colonization and secondary decay. Ultimately, the goal is to overcome the major drawbacks of current direct polymeric restoratives and improve their service life.