Click on image to view larger version.
Figure 1. Representative scanning electron micrographs (SEM) of the dentin side of fractured specimens in different groups. (a-c) Immediate testing, control; (a'-c') immediate testing, chlorhexidine-treated; (d) six-month control, stored in artificial saliva without protease inhibitors; (d') six-month chlorhexidine-treated, stored in artificial saliva without protease inhibitors. C = resin composite; A = adhesive; H = hybrid layer. (a) Low-power magnification demonstrates a mixed failure (partially cohesive in A and C, partially in H). Magnification: 85x. (b) Higher magnification of the area limited by a rectangle in (a), showing cohesive failure in the adhesive layer (A), and failure localized at the bottom (between black arrows) or top (between white arrowheads) of the hybrid layer. Magnification: 500x. (c) Highest magnification of the area limited by the circle in (a), showing cohesive failure in the resin composite and adhesive (R) and in different depths of the hybrid layer (H) (areas separated with dashed line). Magnification: 1500x. (a') Low-power magnification evidences a mixed failure, partially cohesive in A and C and partially in H. Magnification: 85x. (b') Higher magnification of the area limited by a rectangle in (a'), confirming the partial cohesive failures in the adhesive (A) and composite (C). Magnification: 500x. (c') Highest magnification of the circled area in (a'), showing cohesive failure within the adhesive (A), the rest being located at the top of the hybrid layer (T). Most of the exposed dentinal tubules are filled by resin tags (black arrows), while the intertubular dentin seems to be completely covered by adhesive (asterisk). Magnification: 1500x. (d) Highest magnification of control specimen after 6 months’ storage, showing a failure localized in the bottom of the hybrid layer, as evidenced by a high density of the dentinal tubules and an uncovered intertubular dentin, with naked collagen fibrils (asterisk). Magnification: 1500x. (d') Highest magnification of chlorhexidine-treated specimen after 6 months’ storage shows a cohesive failure localized in the middle of the hybrid layer. Dentinal tubules are completely filled by resin tags (black arrow), and intertubular dentin is covered by adhesive (asterisk). Magnification: 1500x.
