Differential DNA methylation at the promoter regions of 12 genes (DCC, KCNA3, KCNA2, RIMS2, HOXB7, PNOC, IRX1, JSRP1, TBX1, OPCML, CECR1, SCN4B) has been detected between periodontitis and clinically healthy tissues [41]. Here, IRX1 is linked to periodontitis.