Pivotal role of filler/matrix interface in dental composites: Review

Dental material research has improved the application and performance of the polymer-based restorative dental composite materials. In spite of these advances, some deficiencies exist in their behaviour. Long term performance of composites is vulnerable due to its polymerization shrinkage and associated shrinkage stresses and also degradation of the filler/matrix interface. Development of low shrinkage resin systems that hinder the volumetric shrinkage and enhancing the quality of the filler/matrix interface has been the ultimate destination for the recent studies. A wide variety of coupling agent materials and techniques are currently available for surface treatment of inorganic fillers in composite materials, however there are still some concerns related to the best coupling agent at the interface that guarantee long term stability and crack resistance of these restorations. The surface modification of the inorganic part of a composite filling material possess a strong potential more than just a bond between the two different phases and can therefore be considered as a medium to compensate the deficits of dental composites. The objective of this article is to review available literatures regarding the improvements made in surface treatments of composite filler particles. Articles that were recently published on this subject focused on the polymer-grafted particles that can be designed with the preferred properties through an appropriate selection of grafting monomers and condition. Application of long chain hydrophobic polymers at the particle surface of composite materials, not only improve hydrolytic stability and uniform dispersion of fillers, but also reduce the polymerization shrinkage and associated stresses which would be very advantageous for restorative dental composites.