Research Seminar Series: Ion-releasing restorative dental composites: materials development and remineralization potential
Prof. Roberto R. Braga
Dept of Biomaterials and Oral Biology, University of São Paulo, Brazil
Long-term clinical studies show overall satisfactory results for resin composite restorations placed in posterior teeth. However, the development of new caries lesions at the margins of composite restorations remains a problem, most noticeably in patients with high caries risk. The formation of new lesions is facilitated by the fact that resin composites retain more biofilm than other restorative materials or enamel. Also, the inevitable presence of retention sites at the restoration margins due to debonding caused by poor adhesive technique, composite polymerization stress, and both hydrolytic and enzymatic degradation of the adhesive layer over time contribute to additional biofilm accumulation. Therefore, the development of restorative composites with some sort of “defense mechanism” against acidogenic bacteria is sought after by numerous research groups. Experimental dental resin composites containing calcium orthophosphate (CaP) nanoparticles were shown to protect enamel against demineralization in the presence of cariogenic biofilm in vitro and in situ. Unfortunately, the incorporation of CaP particles in the composite leads to significant reductions in its mechanical properties due to lack of chemical interaction between the nanoparticles and the resin matrix and also due to the formation of nanoparticles agglomerates with low cohesive strength. This impaired mechanical behavior may limit the clinical use of these bioactive composites to low stress areas. Functionalization of CaP nanoparticles with organic molecules is a viable strategy to reduce agglomeration and improve particle-resin interaction. In this lecture, the challenges of synthesizing organo-modified CaP particles with chemical compatibility with dimethacrylate-based resins and reduced agglomeration will be discussed. Additionally, the effects these nanoparticles have on mechanical properties, long-term stability, ion release and remineralizing potential of experimental bioactive resin-based dental composites will be presented.
Roberto R. Braga graduated in Dentistry in 1992 at the University of São Paulo (USP) School of Dentistry (Brazil) and received both MSc (1995) and PhD degrees (1999) in Dental Materials from USP. He is currently Full Professor and vice-chair of the Department of Biomaterials and Oral Biology at USP. He was visiting professor at Oregon Health & Science University (USA, 2000-2002) and at the University of Sydney (2009-2010). Over the last two decades, his research has focused on dental restorative composites, understanding the influence of compositional variables on their mechanical behavior and polymerization stress development. Recently, he started researching on the synthesis of calcium phosphate nanoparticles, aiming at the development of ion-releasing fillers that could be applied in the development of remineralizing restorative dental composites. He has had several projects funded by FAPESP (The State of São Paulo Research Foundation) and CNPq (National Council for Scientific and Technological Development). He is a fellow of the Academy of Dental Materials and member of Dental Materials editorial board.
For more information, please contact Professor Jay Kruzic.