Methods: Dentin samples were allocated to 8 groups (each n = 10). The contamination of caries infiltrant system (Icon, DMG) was simulated by applying either hydrochloric acid (15% HCl, Icon Etch, 15 s), the resin infiltrant (Icon infiltrant, 4 min) or both prior to the application of the respective adhesives. In the control groups, the etch&rinse adhesive (Optibond FL, Kerr) and the self-etching adhesive (iBond Self Etch, Hereaus) were applied without former contamination with the infiltrant system. Shear bond strength of a nano-hybrid composite was analysed after thermo-cycling (5000x, 5o to 55oC) of the samples. Failure mode was inspected under stereomicroscope at 25× magnification. Data were statistically analysed by two-way ANOVA and Bonferroni-post hoc tests (p < 0.05).
Results: Contamination with hydrochloric acid or with hydrochloric acid and the resin infiltrant reduced shear bond strength (MPa) of the adhesives (Optibond FL: 20.5 ± 3.6, iBOND Self Etch: 17.9 ± 2.6) significantly, while the contamination with the resin infiltrant alone did not impair shear bond strength. Contamination with hydrochloric acid or with hydrochloric acid and the resin infiltrant increased the number of adhesive failures.
Conclusion: The contamination with the caries infiltrant system impaired the shear bond strength of conventional dental adhesives, while the contamination with hydrochloric acid, but not with the resin infiltrant alone was detrimental for the adhesive performance.