In wild‐type periodontitis mice, NAC‐S2 administration decreased the cemento‐enamel‐junction–alveolar bone crest (CEJ‐ABC) distance and the relative mRNA expression of TNF, IL‐6, and IL‐1β, while such phenomena could not be observed in TLR4 deficiency or Myd88 deficiency mice. Here, TLR4 is linked to periodontitis.