MMP9 and periodontal disorder: Increased MMP-8 and MMP-9 levels were observed in advanced periodontal disease compared with healthy subjects; with the discovery of red complex periodontal pathogens (e.g., Porphyromonas gingivalis and Treponema denticola), these biomarkers are used for a more detailed classification of the periodontal disease [14, 21, 22].