Clinical application and research progress of bulk-fill resin-based composites

Traditional resin-based composites have been placed in cavities by incremental layering technique. The shrinkage stress may result in microleakage, post-operative sensitivity which lead to the failed restorations. In 2009, bulk-fill resin-based composites were reported to have the capability to be placed and cured in 4-5 mm increments, because of the improved resin matrix, modified nano-hybrid fillers and new photo initiators. This group of materials can simplify operation in clinical application in addition to decrease shrinkage stress and polymerization shrinkage. The aim of this review is to summarize the classification and properties of bulk-fill resin-based composites and to discuss the development of these new materials in the future.