TNF and obstructive sleep apnea syndrome: There were significant positive correlations of periodontal parameters and cytokine concentrations in saliva between PI and IL-6 in G3 (OSA) (rs = 0.675), PD and TNF-α in G1 (H) (rs = 0.572), and a significant negative correlation between BOP (%) and TNF-α in G3 (OSA) (rs = -0.543).