The amount of IL-1, IL-8, MMP-8, MMP-9, and MMP-13 in saliva samples from patients with periodontal disease and healthy controls have been analyzed and compared [16,17,18], and one study compared hemoglobin levels in blood samples with biomarkers in saliva samples from patients with periodontal disease [19]. The gene discussed is MMP8; the disease is periodontal disorder.