An article pointed out that periodontitis is mostly correlated with NCOA4-mediated ferritinophagy in intracellular iron level regulation [20], p38/hypoxia inducible factor-1α pathway activation, and bromodomain-containing protein 4 and cyclin-dependent kinase 9 transcription modulation mediated butyrate-triggered NCOA4 expression in periodontal ligament fibroblasts [19]. This evidence concerns the gene CDK9 and periodontitis.