Influence of adhesive resin application on shear bond strength of repaired aged-resin composite

Objectives: To assess the efficiency of different adhesive systems on the repair bond strength of resin composite to aged-resin composite substrates and evaluate whether using a silane containing adhesive or introducing silane as an additional step makes a difference.
Methods: A total of 105 cylindrical substrates were fabricated from a nanofill resin composite (Clearfil Majesty Esthetic,Kuraray), aged and treated with silicone carbide paper to standardize the surfaces. Then they were divided into 7 groups of adhesive systems (n=15) which were used as intermediate repairing agents: 1.no tretament, used as control 2. Single Bond Universal Adhesive (3M ESPE) 3. Composite Primer (GC Europe) 4. PQ1 (Ultradent Products) 5. Silane + PQ1 (Ultradent Products) 6. Clearfil Universal Bond (Kuraray) 7. All Bond Universal (Bisco). After the application of adhesives according to the manufacturers' recommendations, specimens were repaired with the same resin composite used to fabricate the substrates. The shear bond strengths were measured using a universal testing machine. Data were analysed by one-way ANOVA and Tukey's post-hoc tests (p=0.05).
Results: The highest bond strength was obtained with Single Bond Universal Adhesive while the lowest result was obtained when resin composite was repaired without using any adhesive layer (control group) (p<0.05). Silane+PQ1 showed statistically higher results than PQ1 and control groups (p<0.05).
Conclusions: Overall, higher shear bond strengths were demonstrated when aged composite resin was repaired with silane-based adhesive systems. Using a silane containing adhesive or introducing silane as an additional step has the same effects on repair. However the results of the study indicate that repair bond strengths of the adhesive systems used are material dependent.