TNF and periodontal disorder: Various components of the GCF, such as cytokines and metalloproteinases (MMPs), like IL-1, IL-6, IL-12, TNF-alpha, VEGF, and MMP9 can be considered periodontal inflammatory markers, their identification in the GCF being used to study the common pathways between periodontal disease and other conditions such as type 1 and 2 diabetes, heart disease, and rheumatoid arthritis [80–82], since the presence of several of these biomarkers has been detected in serum and gingival epithelium of the periodontal-affected patients with some comorbidities [82–85].