MMP8 and periodontitis: However in Heikkinen’s [31] and Yucel’s [35] studies, salivary MMP-8 was significantly elevated in periodontitis patients compared to gingivitis patients, and in Syndergaard’s [10], Yucel’s [35], and Noack’s [36] studies, there were no significant difference in MMP-8 between gingivitis groups and healthy groups.