Mechanical Characteristics of Nanofiller Containing Resin Composites and Clinical Significance

A wide variety of dental resin composites both for use in anterior and posterior areas are available in the dental market. Apart from traditional hybrid, microhybrid and microfilled materials, nanofilled and nanohybrid composites were recently introduced. According to manufacturer claims, these latter products are characterized by high mechanical strength and good wear resistance, low polymerization contraction strain and stress, superior polish and gloss retention. Generally, handling characteristics and clinical performance of resin composite restorations depend on their composition, i.e. the type and amount of matrix monomers and fillers used, the efficacy of the coupling between matrix and filler, and finally the activation system. Although new monomers have been introduced to reduce curing shrinkage and stress, modification of filler concepts, reduction of the filler particle size and increase of filler load seem to be the most significant changes, that might have a direct impact on mechanical characteristics. According to a recent review article on clinical challenges with resin-based restorations, secondary caries and restoration fracture proved to be the most common clinical problems in the long term. Composite fracture was the most frequent type of restoration failures identified within the first five years. Although in vitro trials cannot adequately mimic the complex in vivo conditions, comparative evaluations of basic mechanical characteristics of resin-based restorative materials might hint at their susceptibility to mechanical failure during clinical service. Therefore, the objective of this investigation was to determine several common mechanical characteristics and the degree of cure by depth of six recent nanofiller containing resin composites, compared to one microhybrid and one microfilled reference material. In this presentation composition-property relations will be discussed and clinical recommendations given.