Martins, Ayala, D'Alpino, Calixto, Gomes, Gomes demineralization depths and heterogeneous mono- mer interdiffusion into the dentinal tissue.43 Besides water as a solvent, Adper Single Bond 2 contains ethanol, which has a higher vapor pressure and low dielectric constant and produces hydrogen bridges with water, resulting in a better evaporation rate.3,37 Ethanol also produces a stiffening effect on demineralized collagen, which maintains inter- fibrillar spaces after evaporation.44,45 However, the water molecules contained in the Adper Single Bond 2 adhesive are not sufficient to compensate for the collapsed collagen fibers, which requires previously wet dentin,3 thus increasing the bonding sensibil- ity. Adper Prompt L-Pop and Adper Single Bond 2 have polyalkenoic copolymers, which offer greater resistance to humidity.43 However, this molecule cannot dissolve adequately in adhesive solution; rather it separates into phases, producing globular formations in the adhesive layer.46 According to the manufacturer, the water present in the composition of AdheSE composition does not work as a solvent. ASE has bis-acrilamide molecules, which improve its resistance to degradation. Its methacrylamide molecule has a -CO-NH- or -CO-N- group, which differs from conventional acrilates and methacry- lates in an ester group (-CO-O-R-). It has a simi- larity to collagen amino acids, which promote the formation of hydrogen bridges between carboxyl groups and the amide of the monomers with the carboxyl groups of the collagen.47 The present study indicated the importance of interface integrity over time. It was demonstrated that the conventional etch-and-rinse adhesive sys- tem achieved the highest bond strength values. It is true that the bonding strength values decreased with time, but the results observed for Adper Single Bond 2 after 6 months were still significantly higher than with self-etching systems. Also, despite the lower values, both self-etching adhesive systems demonstrated bond strength stability with time. It was also pointed out that AdheSE was able to ex- hibit lower gap widths under conditions of stress. Based on the results of the present study, the im- portance of obtaining high bond strength levels can be questioned in terms of longevity. It is true that most manufacturers claim higher bond strength values as one of their main advantages. It is true that the self-etching adhesives exhibited lower bond strength values, but the advantages of the simplicity of the technique and the elimination of April 2012 - Vol.6 the rinsing and drying steps cannot be ignored. In this way the possibility of over-wetting or over-dry- ing, which are deleterious to the interface integrity, is reduced. Future clinical studies are necessary to confirm that these characteristics are important to restoration’s longevity. conL usIon Within the limitations of this study, it was con- cluded that: • Despite the higher values, the bonding effec- tiveness of the two-step etch-and-rinse Adper Sin- gle Bond 2 was reduced after water storage; • The one-step, self-etching AdheSE and Adper Prompt L-Pop were not affected by water storage, presenting similar µTBS before and after water storage; and • None of the adhesive systems tested were affected by thermo-mechanical cycling, showing similar microleakage and adhesive gap width be- fore and after cycling stresses. rEFErEncEs 1. De Munck J, Van Landuyt K, Peumans M, Poitevin A, Lam- brechts P, Braem M, Van Meerbeek B. A critical review of the durability of adhesion to tooth tissue: methods and re- sults. J Dent Res 2005;84:118-132. 2. Eick JD, Gwinnett AJ, Pashley DH, Robinson SJ. Current concepts on adhesion to dentin. Crit Rev Oral Biol Med 1997;8:306-335. 3. Van Landuyt KL, Snauwaert J, De Munck J, Peumans M, Yoshida Y, Poitevin A, Coutinho E, Suzuki K, Lambrechts P, Van Meerbeek B. Systematic review of the chemical com- position of contemporary dental adhesives. Biomaterials 2007;28:3757-3785. 4. Leloup G, D'Hoore W, Bouter D, Degrange M, Vreven J. Me- ta-analytical review of factors involved in dentin adherence. J Dent Res 2001;80:1605-1614. 5. Sadek FT, Pashley DH, Ferrari M, Tay FR. Tubular occlusion optimizes bonding of hydrophobic resins to dentin. J Dent Res 2007;86:524-528. 6. Spencer P, Swafford JR. Unprotected protein at the dentin- adhesive interface. Quintessence Int 1999;30:501-507. 7. De Munck J, Van Meerbeek B, Yoshida Y, Inoue S, Vargas M, Suzuki K, Lambrechts P, Vanherle G. Four-year water deg- radation of total-etch adhesives bonded to dentin. J Dent Res 2003;82:136-140. 8. Prati C, Chersoni S, Acquaviva GL, Breschi L, Suppa P, Tay FR, Pashley DH. Permeability of marginal hybrid layers in composite restorations. Clin Oral Investig 2005;9:1-7. 175 European Journal of Dentistry