Collagen Degradation in Endodontically Treated Teeth after Clinical Function
M. Ferrari1,
P.N. Mason2,
C. Goracci1,
D.H. Pashley3, and
F.R. Tay1,4,*
1 Dental Materials and Restorative Dentistry Department, University of Siena, Italy;
2 Restorative Dentistry Department, University of Padua, Italy;
3 Department of Oral Biology and Maxillofacial Pathology, School of Dentistry, Medical College of Georgia, Augusta, GA 30912-1129, USA; and
4 Pediatric Dentistry and Orthodontics, Faculty of Dentistry, The University of Hong Kong, Prince Philip Dental Hospital, 34 Hospital Road, Hong Kong SAR, China;
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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).
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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.
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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.
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