Receiver operating curve (ROC) analysis indicated better diagnostic precision to identify undiagnosed periodontitis for oral fluid biomarkers in adjunct with an interview/questionnaire compared with a plain questionnaire (i.e., risk factors): aMMP-8 AUC (95% confidence interval) = 0.834 (0.761−0.906), total MMP-8 = 0.800 (0.722–0.878), active MMP-9 = 0.787 (0.704–0.870), total MMP-9 = 0.773 (0.687−0.858) and calprotectin = 0.773 (0.687–0.858) vs. questionnaire = 0.764 (0.676–0.851). Here, MMP9 is linked to periodontitis.