In the oral cavity, local cells of the connective tissue (fibroblasts and endothelial cells) form IL-1β, or they are released from leukocytes such as mononuclear cells, macrophages, and polymorphonuclear cells.23 IL-1β results in the widespread expression of the cyclooxygenase 2 gene to produce nitric oxide synthase and metalloproteinase matrix.24 These enzymes themselves activate osteoclasts and bone erosion and collapse type 1 collagen in the bone.25 IL-1β is more important in the stimulation of bone absorption and is an isoform of IL-1 which is more common in periodontitis.26 This evidence concerns the gene PTGS2 and periodontitis.