TRAF2 and periodontitis: In the model of periodontitis induced by oral pseudomonas gingivalis in mice, 4-phenylbutyric acid (4-PBA, an ER stress inhibitor) reversed the significant expression of BIP, XBP1, total XBP1, CTSK, and TRAP genes and the increase in the osteoclast number and bone resorption in alveolar bone.