Malacarne-Zanon et al topology, which is related to the density of the volume by swelling occur with high hydrophilic polymer network.22,24,25 Thus, water may diffuse polymers as longer is the time they stay immersed freely through polymers’ nanoporosities as “un- in a fluid solution.29 This could explain the intense bound” water or it may diffuse tightly attached to silver deposition and the inner penetration of ions polar domains via hydrogen bonding. in materials that are more hydrophilic. According to the “free volume theory,” water In addition to methacrylate monomers, primers can diffuse freely inside the polymer network as and simplified adhesives also contain water and/ unbound water that fills its free volume (pores).26 or organic solvents. Researchers have observed On the other hand, the “interaction theory” de- that the addition of volatile solvents to adhesive fends the idea that water can also diffuse as formulations implies greater water sorption in the “bound” water that tends to disrupt interchain hy- polymerized resin,30 and this corresponds with the drogen bondings, inducing swelling and thus the results obtained in this study. In fact, the exten- opening of additional interchain spaces.27,28 Thus, sion of silver deposition into SB, EX, and OS speci- as the percentage of relatively hydrophilic mono- mens increased if there was more solvent pres- mers (i.e., HEMA, BPDM, PENTA) increases in the ent in their composition, i.e., 25-35%wt, < 20%wt adhesive blend, more sites for hydrogen bonding and 40-70%wt, respectively (Table 1). Although a become available for “bound” water diffusion. For protocol to aid solvent evaporation had been per- consequence, higher opening of additional free formed, it is known that complete solvent elimina- Figure 5. SEM micrographs of a specimen of the adhesive Excite (EX). (A) At low magnification (90 X), a dense granular pattern of permeation (large arrows) can be observed at the interface with adhesive-epoxy resin (R). (*). (B) A higher magnifica- tion (450 X) of the area disignated with * shows a granular deposition of silver along the outer 70-µm of the specimen (large unfilled arrows). October 2010 - Vol.4 Figure 6. SEM micrographs of a specimen of the One-Step adhesive (OS). (A) At low magnification (95 X), an intense silver impregnation can be observed all over the specimen (narrow black arrows and large unfilled arrows). At the interface with ad- hesive-epoxy resin and extending a few microns toward the center of the specimen a granular pattern of deposition is observed (narrow black arrows). A reticular pattern of deposition (large unfilled arrows) can be observed extending through almost the entire thickness of the specimen. The bent surface (narrow white arrows) indicates that the specimen deformed when it was left to dry. (B) A higher magnification (650 X) of areas impregnated with both granular and reticular silver depositions (narrow black arrows and large unfilled arrows). R - epoxy resin. 435 European Journal of Dentistry