TLR4 and periodontitis: Periodontitis is a chronic inflammatory disease triggered by plaque microorganisms in which bacterial components (e.g., lipopolysaccharides) activate the IκB kinase (IKK) complex by binding to host cell-surface receptors (e.g., TLR2/TLR4), leading to the phosphorylation and degradation of IκB, the release of NF-κB into the nucleus, and the initiation of proinflammatory factors (e.g., TNF-α, IL-1β, and IL-6) and matrix metallo proteases (MMPs) transcription [38].