RANKL and OPG are related to periodontal disease, and a balance between them is essential in bone destruction processes.40 In this study, the ephrin/Eph system was modulated by P. gingivalis LPS challenge with a concurrent significant decrease in the RANKL/OPG ratio, which is in accordance with the report14 that the stimulation of PDLFs with LPS leads to increased RANKL expression. This evidence concerns the gene TNFSF11 and periodontal disorder.