Figure 1. Representative SEM micrographs of the status of the collagen fibrils that were present along the coronal third of the root canal walls (i.e., post spaces) of endodontically treated teeth. In the control group, the surfaces were treated with zinc phosphate cement for comparison with the other groups that were retrieved after clinical aging and examined without additional demineralization. (A) Control group. A three-dimensional network of collagen fibrils that covered the entire root dentin surface could be observed. (B) 3–5-year group. The collagen fibrillar network was sparser in appearance, with the entrapment of globular structures (pointers) within the intertubular collagen matrix and the dentinal tubules. (C) 6–9-year group. The structural integrity of the collagen network was lost. Individual collagen fibrils could not be recognized. (D) 10–12-year group. The demineralized collagen matrix was partially missing from the root canal surface, exposing the underlying unetched mineralized dentin (asterisk) and the lateral branches of the dentinal tubules (open arrowhead). Bacteria-like structures were also present (pointer).