Macrophages, T lymphocytes, and other types of cells release chemical mediators, such as interleukin 1β (IL-1β), tumor necrosis factor-alpha (TNF-α), interleukin 17 (IL-17), prostaglandins, and bradykinins, which on reaching high levels indirectly activates the osteoclastogenesis process [5] and can play a fundamental role in the bone resorption associated with apical periodontitis. This evidence concerns the gene IL17A and periapical periodontitis.