Purpose: To evaluate the marginal adaptation of mixed Class V cavities restored with Clearfil Protect Bond (Kuraray), Clearfil SE Bond (Kuraray), and two experimental combinations of both marketed adhesives, after fatigue and water storage. Materials and Methods: Four groups (Clearfil Protect Bond, Clearfil SE Bond, Exp. 1 and Exp. 2) of Class V cavities were restored with a microhybrid restorative composite (Clearfil APX, Kuraray). The marginal quality of these restorations was quantified by evaluation of gold-coated epoxy replicas with scanning electron microscopy before loading, after loading, and after a 12-month period of water storage. Data from marginal adaptation along the total margin length, on enamel, and on dentin were analyzed with the Wilcoxon signed rank test for differences within a group and with Kruskal-Wallis in order to assess the differences between groups. The Bonferroni test was used for post-hoc comparisons, and the confidence level was set to 95%. Results: The mean percentages (±SD) of "continuous margin" of the total marginal length ranged from 79.5% (±13.3) to 62.2% (±10.4) and from 70% (±11) to 61% (±15.1) after loading and after storage, respectively. No significant differences could be detected among the different groups. However, the marginal adaptation of Clearfil Protect Bond remained the most stable of all materials tested, as no significant differences were detected between the percentages of continuous margins before loading, after loading, or after storage. Conclusions: The use of an antibacterial adhesive system was as effective as the conventional two-step self-etching adhesive in the marginal adaptation of Class V restorations. Schlagwörter: marginal adaptation, water storage, MDPB, antibacterial monomer, hydrolytic stability, enamel, dentin