The presence of Porphyromonas gingivalis can increase the RANKL/OPG ratio at periodontitis sites (Belibasakis, Meier, Guggenheim, & Bostanci, 2011; Sakellari, Menti, & Konstantinidis, 2008), and a high RANKL/OPG ratio can facilitate inorganic matrix dissolution by cathepsin‐K and metalloprotease (Bostanci et al., 2008; Mogi & Otogoto, 2007). This evidence concerns the gene CTSK and periodontitis.