Figure 2. TEM of undemineralized specimens of resin-bonded caries-affected dentin. (A) Stained TEM of undemineralized specimens following the application of the self-etch ABF system to caries-affected dentin. The hybrid layer (H; between arrows) was about 3 µm thick, and the underlying undemineralized dentin (U) was highly porous (arrowhead). The dentinal tubule was covered with a smear plug (SP) and was partially obliterated with large caries crystals (pointer). A, filled adhesive. (B) Stained section of the total-etch Single Bond adhesive bonded to caries-affected dentin. A hybrid layer (H) between 15 and 19 µm thick could be seen, with a partially demineralized zone (open arrows) above the undemineralized caries-affected dentin (U). T, dentinal tubule. C, composite. (C) Higher magnification of the basal part of the unusually thick hybrid layer (H) shown in Fig. 2A. Banded collagen fibrils (open arrow) were separated by unusually wide and porous interfibrillar spaces (open arrowheads). A partially demineralized zone (Pd) was present along the demineralization front. This zone was not seen in phosphoric-acid-etched sound dentin (Fig. 1B). U, undemineralized caries-affected dentin.