Salivary interleukin (IL)-1β [12], matrix metalloproteinase (MMP)-8 [13], pyridinoline cross-linked carboxyterminal telopeptide of type I collagen (ICTP) [14], and Porphyromonas gingivalis (Pg) [15] display high prevalence in the populations of interest and are strongly related to periodontitis. This evidence concerns the gene MMP8 and periodontitis.