ABSTRACT
Flowable composite is an appropriate choice for repairing old composite restorations because of its conservative nature, easy application and various colors available on the market, The aim of this study was to evaluate the shear bond strength between old hybrid and new flowable composite resins using Adhes, Single bond, Prompt L Pop and no dentin bonding agents. Eighty acrylic cylinders were fabricated with a standard cavity in the center. Tetric Ceram hybrid composite was placed in the cavities and cured. The cylinders were divided into two groups; one group was kept in water for one month and was then randomly divided into four subgroups. Dentin bonding agents were not used in the first subgroup but the selected bonding agents were applied to the cylinders in the other subgroups. Tetric Flow composite was placed on the primary composite. The same procedure was used for the second group except that the samples were not stored in water for one month. The shear bond strength was measured using a universal testing machine. The data were subjected to LSD variance and independent t-analysis. Shear bond strength values ranged from 33.27 to 16.62 MPa in the first group [in decreasing order: Adhes, Single-bond, control and Prompt L pop subgroups] and from 32.73 to 18.15 MPa in the second group [in decreasing order: Adhes, Single-bond, Prompt L pop and control subgroups]. In the first group, a significant difference was observed between the control versus Adhes and control versus Single bond subgroups and also between the Adhes and Prompt L pop and finally between the single bond and Prompt L pop subgroups. There was no significant difference between the control versus Prompt L pop and Adhes versus Single-bond subgroups. The results obtained in the 2nd group were similar to the first group. The shear bond strength between aged hybrid and new flowable composite resin may increase after application of dentin bonding agents