Abstract
The annual failure rates of composite restorations are low, though most of these failures are due to recurrent caries, fractures of the tooth structure or restorative materials. Volumetric shrinkage has received significant attention because of the role it plays in recurrent decay. In this study, low stress formulations were designed with the ability to release ions through the use of microcapsule technology to combat the causes of recurrent decay. To meet the recommendations of the Scientific Committee on Emerging and Newly Identified Health Risks, the formulations were also designed to be Bis-GMA free. This study examines the flexural strength and fracture toughness of these formulations and explores the effects of different variables on these mechanical properties. The variables include: the type of low stress monomer in the continuous phase, the UDMA/TEGMA ratio within the continuous phase, the amount of glass loaded, the amount of fumed silica loaded, and the inclusion of low viscosity monomers. The study confirms that these variables affect the flexural strength and fracture toughness of the formulations and suggest that there is potential for developing a low stress, BPA free, ion eluting flowable composite/ base liner.