IL18 and periodontal disorder: Given that the anti-inflammatory cytokine IL-10 positively impacts periodontal diseases and the pro-inflammatory cytokine IL-18 is associated with the progression of periodontal disease, the concept that the balance of pro-inflammatory and anti-inflammatory cytokines may be a crucial determinant of clinical outcomes has been explored through studying the IL-18/IL-10 ratio [11, 21–23, 25–27, 35–37].