As key inflammation biomarkers, it is well-documented that periodontitis is linked to increased levels of proinflammatory cytokines [IL-6, tumour necrosis factor alpha-TNF-α, matrix metalloproteinase-8 (MMP-8), IL-1β][37] and reduced levels of anti-inflammatory cytokines (IL-8 and IL-10) in saliva and periodontal tissues[38-42]. This evidence concerns the gene MMP8 and periodontitis.