Matrix metalloproteinases (MMPs) form a family of enzymes that mediate multiple functions both in the tissue destruction and immune responses related to periodontal inflammation. The expression and activity of MMPs in non-inflamed periodontium is low but is drastically enhanced to pathologically elevated levels due to the dental plaque and infection-induced periodontal inflammation. Soft and hard tissue destruction during periodontitis and peri-implantitis are thought to reflect a cascade of events involving bacterial virulence factors/enzymes, pro-inflammatory cytokines, reactive oxygen species and MMPs. However, recent studies suggest that MMPs can also exert anti-inflammatory effects in defence of the host by processing anti-inflammatory cytokines and chemokines, as well as by regulating apoptotic and immune responses. MMP-inhibitor (MMPI)-drugs, such as doxycycline, can be used as adjunctive medication to augment both the scaling and root planing-treatment of periodontitis locally and to reduce inflammation systematically. Furthermore, MMPs present in oral fluids (gingival crevicular fluid (GCF), peri-implant sulcular fluid (PISF), mouth-rinses and saliva) can be utilized to develop new non-invasive, chair/bed-side, point-of-care diagnostics for periodontitis and dental peri-implantitis.

Periodontitis are infectious diseases characterized by immune-mediated destruction of periodontal supporting tissues and tooth loss. Matrix metalloproteinases (MMPs) are key proteases involved in destructive periodontal diseases. The study and interest in MMP has been fuelled by emerging evidence demonstrating the broad spectrum of molecules that can be cleaved by them and the myriad of biological processes that they can potentially regulate. The huge complexity of MMP functions within the ‘protease web’ is crucial for many physiologic and pathologic processes, including immunity, inflammation, bone resorption, and wound healing. Evidence points out that MMPs assemble in activation cascades and besides their classical extracellular matrix substrates, they cleave several signalling molecules—such as cytokines, chemokines, and growth factors, among others—regulating their biological functions and/or bioavailability during periodontal diseases. In this review, we provide an overview of emerging evidence of MMPs as regulators of periodontal inflammation.

The aim of this study was to investigate the utility of incorporating active matrix metalloproteinase-8 (aMMP-8) as a biomarker into the new periodontitis classification system (stage/grade) presented in 2018. This study included 150 Greek adults aged 25–78, of whom 74 were men and 76 women. Participants were tested with an aMMP-8 point-of-care mouthrinse test, after which a full-mouth clinical examination was performed to assess their periodontal and oral health. The aMMP-8 levels in mouthrinse were significantly lower among healthy patients compared with patients in more severe periodontitis stages and grades (Kruskal–Wallis test and Dunn–Bonferroni test for pairwise post-hoc comparisons; p < 0.01 and p < 0.05, respectively). Furthermore, aMMP-8 levels were less correlated with plaque levels than bleeding on probing (BOP) (Spearman’s rho = 0.269, p < 0.001; Spearman’s rho = 0.586, p < 0.001); respectively). Thus, aMMP-8 was more robust to the confounding effects of oral hygiene than traditional periodontal parameter bleeding on probing. The aMMP-8 point-of-care mouthrinse test can be utilized as an adjunctive and preventive diagnostic tool to identify periodontal disease, classified by stage and grade, and ongoing periodontal breakdown chairside in clinical practice in only 5 min. Overall, integrating aMMP-8 into the new periodontitis classification system seems beneficial.

Objective— In culture studies matrix metalloproteinase (MMP)-8 thins the protecting fibrous cap of the atherosclerotic plaque thereby increasing its vulnerability. Results on the association of serum MMP-8 concentrations and cardiovascular diseases (CVD) are, however, scarce and contradictory. Methods and Results— We analyzed the association between CVD or subclinical atherosclerosis and serum MMP-8 and tissue inhibitor of metalloproteinase-1 (TIMP-1) concentrations of 1018 men with the follow-up time of 10 years. MMP-8 concentrations or MMP-8/TIMP-1 ratios were higher in men with prevalent CVD or subclinical atherosclerosis at baseline than those without. In men free of CVD at baseline, MMP-8 concentrations associated with acute myocardial infarction, death from coronary heart disease (CHD), CVD, or from any cause with relative risks (RR) (95% CI) of 1.138 (1.009 to 1.284), 1.188 (1.034 to 1.365), 1.171 (1.026 to 1.338), and 1.136 (1.018 to 1.269), respectively, and MMP-8/TIMP-1 ratio with CHD death with an RR of 1.206 (1.028 to 1.414) per standard deviation (SD) increase. In men with no prevalent CVD but with subclinical atherosclerosis at baseline, elevated serum MMP-8 concentration predicted CVD death with an RR of 3.03 (1.09 to 8.44). TIMP-1 concentrations alone had no predictive value. Conclusions— The results indicate that serum MMP-8 concentrations are elevated in prevalent or subclinical atherosclerosis and associate with the worst cardiovascular outcome.