Pulpitis and periapical periodontitis, periodontal disease are commonly characterized by the chronic inflammation caused by Gram- negative bacteria infection. Lipopolysaccharide（LPS） is a major component of the outer membrane of Gram- negative bacteria. CD14 and Toll - like receptor 4（TLR4） belong to the class of LPS receptors. TLR4 has received much attention as a member of LPS receptors recently and may be a key factor in the pathogenesis of pulpitis and periapical periodontitis and periodontal disease. The article reviews the recent progress of TLR4.
