Composite resins have been used for more than 30 years in the posterior zones (Opdam et al., 2010 ; Pallesen and Van Dijken, 2015). The adhesion of these materials to dental tissues thanks to an adhesive system allowed to develop the tissue-saving concept. They also meet the patients' esthetic demands. Moreover, direct restorations are time- and cost-saving techniques compared with indirect restorations and it is relatively easy to repair them, which is why they are the most commonly used restoration materials in daily practice.
The mechanical and physical properties of these materials have been improved over the years but there are still drawbacks among which the removal as well as the polymerization stress and depth. Indeed, the cure shrinkage increases the risk of adhesion and sealing loss, generating in the short or longer term recurrent caries. These and the fractures are always the main causes of failure in posterior restorations (Astvaldsdottir et al., 2015). Polymerization shrinkage which is the weak link of methacrylate-based composite resins (Leprince et al., 2013) is proportional to the quantity of resin and the depth of polymerization does not exceed two millimeters (standard ISO 1.5mm dentin, 2mm enamel). Practitioners must thus work with increments (Wieczkowski et al., 1988) and this technique cannot reduce polymerization stress (Verslui et coll., 1996).