Comparing the Healing Potential of Late-Stage Periodontitis and Peri-Implantitis
Peri-implantitis is defined as an inflammatory disease affecting the tissues around osseointegrated functioning implants. Unfortunately, detailed peri-implantitis pathogenesis is not well understood and current treatments lack predictability. Compare the healing potential of late-stage ligature-induced periodontitis and peri-implantitis after ligature removal. Four-week-old C57BL/6J male mice had their left maxillary molars extracted. After 8 weeks, implants were placed in healed sockets and allowed to osseointegrate. Mice were separated into control (no ligature) and experimental (ligature) groups. In the experimental group, ligatures were placed around the implant and the contralateral second molar. Four weeks later, the ligature group was randomly divided into ligature-retained and ligature-removed groups. Mice were sacrificed at 2 time points: 1 and 2 weeks after ligature removal. The samples were analyzed by microcomputed tomography (micro-CT) and histology. Ligature-induced significant bone loss in peri-implantitis and periodontitis were compared with respective controls. At the 2-week time point, bone formation was observed in the ligature-removed groups compared with respective controls; however, more bone was regained in periodontitis ligature-removed compared with the peri-implantitis ligature-removed group. Histologically, the peri-implantitis ligature-retained group had higher inflammatory levels and a higher number of osteoclasts compared with the periodontitis ligature-retained group. Moreover, in the peri-implantitis ligature-retained group, collagen appeared less organized compared with the periodontitis ligature-retained group at both time points; although collagen tended to reorganize following ligature removal in both conditions. Peri-implantitis does not respond to treatment as well as periodontitis. Future work includes understanding peri-implantitis pathogenesis and developing predictable treatment protocols.
Schematic diagrams. (a) Schematic diagram depicting the timing of the experimental design. (b) Schematic diagram specifying the number of samples that were used for the study.
Representative clinical images and micro-computerized tomography (micro-CT) analysis of periodontitis and peri-implantitis after insult removal. (a) Representative clinical images of control (no ligature), ligature-retained, and ligature-removed groups of teeth (periodontitist) and implants (perio-implantitis) at magnification ×50. Images were taken after 1 (top row) and 2 (bottom row) weeks of insult removal. Soft tissue edema present in periodontitis and peri-implantitis ligature-retained groups subsided following ligature removal for both conditions. (b) Representative sagittal micro-CT images of control (C), ligature-retained (L), and ligature-removed (Rx) groups of teeth (periodontitis) and implants (peri-implantitis) 1 and 2 weeks after insult removal. (b) Graphs represent the averaged distance from the cementoenamel junction to the alveolar bone crest in teeth and from the implant head to the alveolar bone. Data are mean ± SEM. *P < .05, **P < .01, ***P < .001 (n ≥ 3 for all groups/time points). Note that once ligature was removed, the teeth regained more bone compared with the implant ligature-removed group.
Histologic evaluation after insult removal in periodontitis and peri-implantitis. Representative sagittal hematoxylin and eosin (H&E) images of control (C), ligature-retained (L), and ligature-removed (Rx) groups 1 and 2 weeks after insult removal in periodontitis and peri-implantitis. (a, b) 1-week time point of periodontitis and peri-implantitis at magnifications ×100 and ×200 (c, d) 2-week time point of periodontitis and peri-implantitis at magnifications ×100 and ×200. Note higher levels of inflammation in peri-implantitis control, ligature-retained, and ligature-removed groups as compared with the respective periodontitis groups. Also note new bone formation in periodontitis, which is concentrated around the periodontal ligament area. New bone formation was minimal in peri-implantitis groups. Yellow arrows point at bone formation sites, evident by reversal lines.
Osteoclast numbers after insult removal in periodontitis and peri-implantitis. (a) Representative sagittal of tartrate-resistant acid phosphatase (TRAP) stained images of control, ligature-retained, and ligature-removed groups 1 and 2 weeks after insult removal in periodontitis and peri-implantitis at magnification ×10. (b) Graphs represent the averaged number of osteoclasts at 1 and 2 weeks after insult removal in periodontitis and peri-implantitis groups normalized to their respective controls (n = 3/group/time point). *P < .05, **P < .01 (n ≥ 3 for all groups/time points).
Collagen organization after insult removal in periodontitis and peri-implantitis. Representative sagittal images of picrosirius red staining under polarized light of control, ligature-retained, and ligature-removed groups 1 and 2 weeks after insult removal in periodontitis and peri-implantitis at magnification ×10. Note greater and more organized type 1 collagen (yellow birefringence) in periodontitis vs peri-implantitis across all groups and time points.
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