Pathogen-associated molecular patterns (PAMPs) are conservative molecules associated with groups of pathogens or their products. These molecules are recognized by relevant receptors. PAMPs induce the expression of inflammatory cytokines through the signal cascade. The role of PAMPs in the initiation and development of periodontitis is recently attracting attention. PAMPs induce the expression of inflammatory mediators after they are recognized in the periodontium. This process damages the periodontal soft tissue and osseous tissue, thus resulting in periodontitis. The results of this study will provide an excellent resolution for the treatment of periodontitis by blocking the pathogenic pathway of PAMPs.