IL17A and periodontitis: Unlike Th1 cells, Th17 cells mainly secrete the pro-inflammatory factors IL-6, IL-17 and IL-23 to regulate the development of periodontitis, among which IL-17 can promote periodontal connective tissue and alveolar bone destruction by regulating the expression levels of prostaglandin E2 (PGE2), matrix metalloproteinases (MMPs) and RANKL (Cheng et al., 2014; Dutzan and Abusleme, 2019; Huang et al., 2021; Kini et al., 2022).