Permeability of dental adhesives tion is difficult, if not impossible, especially from trees was also observed in OS micrographs. In high hydrophilic blends.31-33 Therefore, residual previous work,35 a great agitation of molecules was volatile solvents diluted in the liquid adhesive observed during the polymerization of an acetone- may have prevented the approximation between solvated resin. Researchers pointed out that such reactive pendant species, making cross-linking agitation was due to the fast acetone volatilization, reaction more difficult.34 Thus, instead of achiev- which is favored by the increase in temperature, ing optimal macromolecular packing density, the that results from the polymerization reaction, and polymer backbone may have had its free volume by acetone’s low boiling point (56°C) and high va- greatly augmented to a level directly related to the por pressure (200 mmHg at 25°C).35 We speculate amount of organic solvent present during polym- that the reticular pattern of infiltration observed in erization, even though a good degree of conver- OS occurred due to the great agitation of acetone sion was achieved.34 molecules that could not escape from the speci- The effect of solvent presence in an adhesive men because of the presence of the glass slide. composition seemed to be more marked in OS, A greater silver deposition, accompanied by the system with the higher concentration of sol- several cracks, was observed in AP micrographs. vent (acetone). Beyond the granular pattern of The higher amount of hydrophilic monomers in silver deposition, which is the result of silver pre- AP, compared to the other tested materials, could cipitation in free space, a reticular pattern of silver be responsible for the faster and larger uptake of precipitation resembling what is known as water- silver8,36 that ended up permanently damaging the Figure 7. SEM micrographs of a specimen of the adhesive Adper Prompt (AP). (A) At Figure 8. SEM micrographs of a specimen of the adhesive One-Up bond F (OU). (A) At the lowest magnification (110 X), an intense silver deposition can be observed over low magnification (100 X), a granular deposition occupies much of the outer surfaces the entire thickness of the specimen. Irregular margins represent the distortion (upper and lower) (narrow black arrows), becoming more sparse in the center of that occurred in the specimen during storage in the tracer solution (narrow arrows). the specimen. A reticular silver deposition was also observed, but it was restricted A crack is observed emerging from the specimen (◄). (B) At a higher magnification to a few areas (large unfilled arrows). (B) A higher magnification (330 X) of the area (350 X), one can see that the silver deposition occurred predominantly in the form limited with a rectangle in A. R- epoxy resin. of thin, elongated structures (large unfilled arrows), similar to the ones observed in the SB specimens (Fig. 4). R – epoxy resin. 436 European Journal of Dentistry