MMP9 and Peri-Implantitis: Although MMP-8 is considered as the main collagenase in active peri-implantitis [92], MMP-9 has also been shown to be involved in the pathogenesis of peri-implantitis [93] via a LOX-1 (lectin-like oxidized low-density lipoprotein) and Erk1/2 (extracellular signal-regulated protein kinase) mechanism that has been suggested as a potential target for decreased inflammation and increase apoptosis in peri-implantitis.