Figure 2. TEM micrographs of bonding of Single Bond to laser-ablated, deep dentin. (a) A low-magnification overall view of the resin-dentin interface. A 3- to 5-µm-thick laser-modified layer (Ab) could be observed that had separated from the underlying intertubular dentin (D). The resultant space (S) was infiltrated by the laboratory-embedding resin. Remnant dentinal tubules (arrow) could be seen within the laser-modified layer. A, adhesive layer. Bar = 1 µm. (b) A high-magnification view of the superficial part of the laser-modified layer that was partially infiltrated by the polyalkenoic acid copolymer (P). Roughly parallel plates of rippled materials could be identified (arrow). Bar = 1 µm. (c) A high-magnification view of the basal portion of the laser-modified layer. Collagen fibrils in this region were fused together to form an amorphous layer (F) that was completely devoid of interfibrillar spaces. This layer probably restricted resin infiltration into the laser-ablated intertubular dentin (D). Above the fused layer, a circumferential layer of mineral-rich peritubular dentin (arrow) could be seen around a dentinal tubule (T). Because of its higher mineral content, peritubular dentin was ablated to a lesser extent than the adjacent collagen-rich intertubular dentin. E, epoxy resin. Bar = 300 nm. (d) A very high-magnification view of the base of the laser-modified layer. Beneath the fused layer (F), collagen fibrils from the subsurface intertubular dentin were also partially denatured and appeared as unraveled, microfibrillar strands (arrow). No collagen banding could be seen along the intact collagen fibrils in the subsurface zone for several microns in the underlying dentin. Bar = 100 nm.