CXCL8 and periodontal disorder: Among the 12 cytokines, seven had undetectable concentrations at BL (IL‐1β, IL‐8, b‐FGF, G‐CSF, GM‐CSF, MIP‐1β, and TNF‐α), a finding that suggests that these specific biomarkers are not the most appropriate when studying the relationship of periodontal disease and/or periodontal treatment with the systemic response.