Dental composites were a revelation when they were introduced into the market. Even though they have kept evolving by becoming mechanically stronger, less technique sensitive and aesthetically appealing, they are still not easy to place and fail due to bacterial microleakage which leads to recurrent caries. Therefore, they have not been the staple material of choice for paediatric patients since they are not as reliable as preformed metal crowns long-term. AIMS AND OBJECTIVES: The aim of this project was to develop novel SMART composites which will target the paediatric patient. They have antibacterial polylysine and remineralising MCPM incorporated in them which could potentially address the bacterial microleakage problem of existing materials. They are self-etching and can be used as a bulk filling after soft caries removal. Good monomer conversion at depth and dimensional stability are essential for bulk filling and prevention of microleakage respectively and therefore the focus of this work. METHODS: An FTIR machine was used to measure the monomer conversion at 2 different sample depths (1mm, 2mm) with three different curing times (10s, 20s, 40s) in order to determine the effect of low versus high MCPM and PLS. In addition, mass and volume change was measured and shrinkage was calculated in order to determine the volumetric stability of the SMART composites. To assess microleakage, a dye test was performed in natural primary teeth drilled and directly filled with the SMART composite. This had the highest MCPM and PLS content. Three commercial materials which included Activa (following tooth etching) and two glass ionomer cements were used as comparators. RESULTS: Antibacterial polylysine and remineralising MCPM had negligible effect on monomer conversion. Volume change (2%) upon water sorption could help balanced polymerization shrinkage (3%). Microleakage of the SMART composite was equivalent to Activa but less than the glass ionomer cements. CONCLUSION: SMART composites good monomer conversion, volumetric stability, microleakage resistance and ease of placement should enable a more viable and predictable composite restorative paediatric option in the future
