TNF and periodontitis: sTNF-α: Serum tumor necrosis factor-alpha, sIL-10: Serum interleukin-10, sNO: Serum nitric oxide, sPGE2: Serum prostaglandin E2, GCF: Gingival crevicular fluid, PSS: Periodontitis staging system (due to the insufficient number of PSS 1 and PSS 2 samples, both were included in the same group and evaluated)