The plotted ROC curves showed a good predictor value for the MMP-9/TIMP-1 ratio, the (MMP-8 + MMP-9)/TIMP-1 ratio and the MMP-8 + MMP-9 sum (as top three), followed by the MMP-8/TIMP-1 ratio, HGF, MMP-2, and OPG for differentiation of periodontitis versus gingivitis conditions (AUC ≥ 0.85). This evidence concerns the gene MMP9 and gingivitis.