The effect of storage on shear bond strength of three composite resins to dentin

The aim of this study was to determine the effect of storage time on shear bond strength of three composite resin, two utilize total etch technique and one utilize self etching bonding agent. One hundred twenty maxillary and mandibular molars were used in this study. The teeth were prepared by cutting the occlusal enamel with diamond bur to expose dentin and ground wet with silicone carbide papers. The specimens were then divided into three groups and stored in distilled water. Scotchbond Multipurpose Plus was used in the first group and a stainless steel round mould, with a central hole of 4 mm in diameter and 2 mm in height was used to build up the composite Z100. The composite resin was inserted in two increments, each one was light cured for 40 seconds. This gro-up is divided into four subgroups each of ten according to the storage time (one day, fifteen days, three months and six months) then stored in distilled water accordingly. The same procedure was repeated in the second and third groups. The composite used in the second group was Tetric with Excite bonding agent. In the third group, Definite composite and its bonding agent Etch and Prime was used. The bond strength was measured and the data were statistically analyzed. Z100 composite had the greatest shear bond strength followed by Tetric and Definite. One day and fifteen days storage time for all types of composite had greater shear bond strength than the three months and six months storage time. In conclusion there was a gradual decrease in bond strength with increased storage time up to six months irrespective of the type of composite.