Figure 2. Unstained, undemineralized TEM micrographs of oxalate-desensitizer-treated acid-etched dentin specimens that were bonded with single-bottle total-etch adhesives. The bonded specimens were immersed in an ammoniacal silver nitrate tracer solution before laboratory dehydration and epoxy resin embedding. U: undemineralized dentin. (A) A specimen from the PB-SS subgroup, showing extensive nanoleakage (open arrowheads) in the hybrid layer (H) and the dentinal tubule (T). Electronlucent spherical globules (pointer) were depicted in the adhesive layer (A). Silver deposits were occasionally seen within the spherical globules. Discontinuous electronlucent structures with a scalloped margin could be identified along the adhesive-hybrid layer interface (open arrow). Electronlucent crystals, probably representing the calcium oxalate crystals (arrow), were also seen in the dentinal tubules at a position that was 8–10 µm from the dentin surface. (B) A specimen from the OB-BB subgroup, showing fairly extensive nanoleakage (arrowhead) within the hybrid layer (H). Discontinuous electronlucent deposits, with scalloped margins resembling conglomerates of spherical globules (pointer), could be identified along the adhesive-dentin interface. Subsurface electronlucent deposits (asterisk) were also observed in the dentinal tubules (T). (C) A high-magnification view of the hybrid layer in the SB-BB subgroup. Only isolated spots of silver grains (arrowhead) were observed in the hybrid layer (H). No globular structures were identified on the surface of the hybrid layer. The dentinal tubules (beneath the position of the hybrid layer) were blocked by subsurface electronlucent deposits (asterisk). P: polyalkenoic acid copolymer component of the adhesive. (D) A high-magnification view of subsurface angular crystalline deposits (asterisk) within the dentinal tubule (T) in the OS-BB subgroup. No surface globular structures could be identified. Silver deposits (arrowhead) were occasionally observed within the hybrid layer (H). A: adhesive.