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.