Current dental restorative materials include tooth-colored materials called composite resins, which are made of a resin matrix and an inorganic filler coated with a silane coupling agent. Composite resins can shrink considerably upon setting. This shrinkage stress can generate gaps along the composite/dentin interface. Low-viscosity fluid resins and primers have been used to bond composite resins to dentin. The adhesive resin layer may be able to act as an elastic medium and compensate for the polymerization stresses that develop within the composite resin. The hypothesis tested in this study was that the use of a “stress-absorbing” intermediary dentin adhesive would result in lower incidence of gaps at the restoration/cavity interface and in a thicker resin/dentin interdifusion layer or hybrid layer.

Dentin disks with a thickness of 900 um±100 μm were obtained from extracted human molars and assigned to two adhesive systems (One-Step [OS] and Single Bond [SB]), three degrees of intermediary “stress-absorbing” treatments (none, Scotchbond Multi-Purpose [SBMP], and OptiBond FL [OB]) and two composite resins (Ælite-Flo [ÆF] and Z100