Resin based composite materials are the most used materials for the direct restoration of posterior teeth today. They have significantly improved over the years, leading to better mechanical and esthetic properties and clinical durability, but the polymerization shrinkage and polymerization stress, as well as time-consuming placement due to limited polymerization depth remain the greatest disadvantages. In response to a part of the problem bulk-fill composite materials have appeared. Low-shrinkage monomers, more potent photoinitiators, modifications in size and volume of fillers are some of the alterations made in regard to conventional composite resins. Owing to them the filling process is faster because it is possible to place them in 4-5 mm thick layer. While innovating properties reduce polymerization stress, the degree of conversion remains satisfactory. The placement technique of the bulk-fill composite materials is conditioned by their composition,thus low-viscosity, high-viscosity, sonic-activated and dual-polymerizing bulk-fill materials can be distinguished. Low-viscosity bulk-fill composites require at least one additional layer of a high-viscosity composite, whether it is conventional or bulk-fill composite, to protect them from the abrasive action of antagonistic teeth. Unlike them, high-viscosity bulk-fill composites can be used on their own. Sonic-activated bulk-fill composite materials are in fact high-viscosity materials whose visosity is reduced by ultrasonic vibrations from a special handpiece used for their application. Thanks to sonic activation, a better cavity adaptation is achieved. Dual-polymerizing bulk-fill composites can be placed in layers thicker than 4-5 mm due to the chemical polymerization which enables monomer cross-linking even in deep parts of the cavity with no light penetration from the curing unit. At the same time, light polymerization of the superficial layer of the filling protects it from the influences of the oral cavity. Laboratory and clinical studies made up to this point have demonstrated that the quality and longevity of bulk-fill composites are equal those of conventional composites.