The Pg-LPS-induced increase in TNF-α production from gingival epithelial cells has been reported to correlate with the initiation of connective tissue destruction and bone resorption.36,37 TNF-α is thought to play both facilitative and suppressive roles in the pathogenesis of periodontal disease.10 The significance of the Pg-LPS-induced TNF-α observed in the present study in the pathogenesis of periodontal inflammation remains unclear. This evidence concerns the gene TNF and periodontal disorder.