Figure 4. TEM images of regions that were close to the GIC-dentin interfaces. (A). The GIC-dentin interface in ChemFlex showed the presence of a 3-µm-thick, partially demineralized, intermediate layer (IL; between open arrows) between the dentin (D) and the fractured GIC (GIC). The originally intact GIC was fractured during ultramicrotomy. FASG fillers (pointer) with a peripheral siliceous hydrogel layer (arrowhead) could be seen within the remnant GIC. T, dentinal tubule. (B) A high-magnification view of the polyalkenoate matrix (M) from a dentin specimen that was bonded with the experimental GIC K-136 (Dentsply DeTrey). Siliceous hydrogel layers (pointer) could be seen along the periphery of the FASG fillers (G). Within the siliceous hydrogel layer, numerous "seed-like", electron-dense fluoride-rich phases could be observed (open arrows). (C) A high-magnification view of the polyalkenoate matrix that was sectioned close to the GIC-dentin interface in ChemFlex. A portion of the wall of a hollow spherical body (S) could be seen. This wall resembled the adjacent polyalkenoate matrix (M) in ultrastructural appearance, but was separated from the latter. ESp, empty space that was occupied by the Formvar-coated copper grid.