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Figure 3. Representative TEM micrographs of collagen fibrils that were present along the surfaces of post spaces in the 10–12-year group of endodontically treated teeth. (A) A low-magnification view of the surface of the root dentin, depicting a surface zone of 1–4 µm thick (between dotted lines) in which the collagen fibrils were denatured and appeared different from the banded collagen fibrils that were present in the underlying intact root dentin (D). Within this surface zone, there were also regions in which the collagen fibrils were completely broken down (asterisk). The root dentin surface was covered with bacteria (B), some of which had disintegrated with only the electron-dense cell walls remaining (open arrowheads). Remnant luting cement could also be identified (arrows). ER: epoxy resin. (B) A high-magnification view of the denatured zone, showing the breakdown of denatured, unbanded collagen fibrils into a mesh of disorganized microfibrils (open arrowhead). Adjacent collagen fibrils were sparsely arranged (asterisk) and were thinner than the intact banded fibrils (arrow) from the underlying root dentin. (C) A high-magnification view taken from a region in which the collagen fibrils had partially disappeared (between open arrows), with only traces of microfibrillar strands remaining. Intact, banded collagen fibrils (arrow) could occasionally be seen in the underlying root dentin (D). B: bacteria. (D) Distribution of exposed collagen fibrils on dentin surface lining post-space over clinical service in years. Values are percent of the total specimens per time period.
