Permeability of dental adhesives less sensitive and simpler to apply. To make ad- As silver particles are carried through poly- hesives able to demineralize, infiltrate and bond mers while dissolved in water, silver tracer pen- with dentin in fewer steps, hydrophilic monomer etration within polymerized adhesives may be and organic solvent contents have been increased interpreted as a visual exhibition of the water in the formulation of adhesives. Hence, it is not diffusion process. Thus, factors related to the in- surprising that the most simplified systems tested creased water sorption in these adhesive systems in this study (AP and OU), the so-called “all-in- may also explain the greater silver permeation one” adhesives, exhibited a higher amount of sil- and deposition. Water sorption into polymer net- ver deposits than the adhesives SB, EX, and OS, works is predominantly controlled by two main which represent the two-step “etch-and-rinse” factors: resin polarity, which is dictated by the adhesives. Conversely, the bonding agents of the concentration of polymer polar sites available to systems SE and MP, which are composed of more form hydrogen bonds with water,22,23 and network hydrophobic comonomers (i.e., Bis-GMA), exhib- ited significantly lower depositions of silver, which were restricted to the specimen’s surfaces. There- fore, the hypothesis that there is no difference in permeability to silver nitrate solution among the tested adhesives cannot be accepted. Figure 3. SEM micrographs of a specimen obtained with the mixture of the primer Figure 4. SEM micrographs of a specimen of the adhesive Single Bond 2 (SB). (A) and the bond components of the Clearfil SE Bond system (SE-PB). (A) At low mag- At low magnification (90 X), two patterns of silver infiltration can be identified: a nification (90 X), it appears that the deposits of silver were restricted to the 50-µm granular deposition localized in the outer portions (upper and lower) of the speci- outer surface of the specimen, in contact with the epoxy resin (narrow arrows). men that extends to its center (large unfilled arrows); and a reticular impregnation (B) However, at higher magnification (400 X), a multi-phase material can be seen; in the center of the specimen, forming thin, elongated structures (black arrows). whereas in the center of the specimen the silver is sparsely deposited, its periphery (B) Higher magnification (400 X) of the area shows that it is impregnated with the is densely impregnated (*) by a foggy line that extends along the interface of the granular pattern of silver deposition (large unfilled arrows). (C) Higher magnifica- adhesive-epoxy resin. Such phase variability denotes that the primer and the bond tion (1,200 X) of the area wherein the silver impregnation formed shows elongated components of the Clearfil SE system did not mix well. R-epoxy resin. structures (black arrows). R- epoxy resin. 434 European Journal of Dentistry