According to the logistic regression model for MMP-9 (Table 3), MMP-9 algorithm was MMP-9-score = -14.936 + 0.052*MMP-9(ng/ml) + 0.009*age(year)+ 1.87*sex+ 2.433*smoking—2.517*drinking + 1.53* education level -0.447*physical exercise + 0.825*periodontitis + 0.512* obesity—0.302*diabetes + 2.741*hypertension + 3.434*hypercholesterolemia. The gene discussed is MMP9; the disease is periodontitis.