MMP9 and periodontitis: The results showed significant differences in the detection of P. gingivalis (p < 0.001), P. intermedia (p < 0.01), P. nigrescens (p < 0.001) and T. forsythia (p < 0.001), but also in the levels of MMP-8 and MMP-9 in GCF between patients with and without periodontitis.