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Figure 2. Representative TEM micrographs of collagen fibrils that were present along the surfaces of post spaces in the 3–5-year group of endodontically treated teeth. (A) A low-magnification view of the surface of the root dentin, showing the presence of electron-dense luting cement (asterisk) and cement particles (arrow) within the dentinal tubules (T). The surfaces of the collagen fibrils (pointer) appeared more sparse than those from the underlying intact root dentin (D). ER: epoxy resin. (B) A high-magnification view, showing a region immediately beneath the luting cement (asterisk) in which the collagen fibrils were sparsely arranged and denatured (pointer). ER: epoxy resin. (C) A high-magnification view of the root dentin surface, showing the disappearance of collagen banding and partial unraveling of the microfibrils (open arrowheads) within the collagen fibrils. These features are indicative of the presence of collagenolytic activity along the surface of the post space that was probably in contact with oral fluid. Banded collagen fibrils could be identified only occasionally (open arrow) from the underlying root dentin.
