MMP-8 in saliva was similar in composition to its counterpart within the gingival sulcus (Gangbar et al., 1990), and a similar pattern of elevated MMP-8 was observed in the gingival sulcus of peri-implantitis to that observed at the site of periodontitis (Ma et al., 2000; Arakawa et al., 2012; Janska et al., 2016). The gene discussed is MMP8; the disease is periodontitis.