MMP8 and Peri-Implantitis: [34] When proinflammatory and matrix degrading responses of gingival and granulation tissue fibroblasts to an in vitro challenge to Porphyromonas gingivalis (P. gingivalis) were compared between subjects with healthy periodontium and patients with periodontitis and peri-implantitis lesion, MMP-8 expression was found higher in nonchallenged peri-implantitis fibroblasts than in fibroblasts from healthy periodontium.