A laboratory evaluation of bulk-fill versus traditional multi-increment-fill resin-based composites.

Some concerns exist, however, regarding bulk-fill composites. One proposed rationale for limiting composite increments to 2 mm is to allow the curing light to penetrate to the resin farthest away from the light source.1,2 A second reason for using 2-mm increments is to minimize the shrinkage and shrinkageinduced stress associated with composite polymerization. Contraction stresses that exceed the adhesive strength of the composite may result in gaps between composite and cavity walls.3-5 It is widely believed that these marginal gaps may lead to microleakage, sensitivity and secondary caries,1,6-11 although there is little clinical evidence to support that secondary caries are caused by this gap formation.3,12