The expression distribution of methyltransferase-related genes was further analyzed, and it was observed that EZH2, DNMT1 and DNMT3B were significantly upregulated in normal samples (Figure 1B, 1C, 1E), whereas that of DNMT3A was sharply downregulated (Figure 1D), indicating that histone methylation and DNA methylation were abnormal in periodontitis. This evidence concerns the gene EZH2 and periodontitis.