MMP8 and Peri-Implantitis: Regarding the irreversible tissue destruction pathogenesis of oral diseases, periodontitis and peri-implantitis, as well as systemic diseases such as diabetes, sepsis, meningitis, kidney diseases, pancreatitis, chronic obstructive pulmonary disease (COPD), cardiovascular diseases (CVD) and cancers; the key collagenolytic MMP has been demonstrated to be aMMP-8 (i.e., collagenase-2/neutrophil collagenase) [18,19,20,21,22,23,24,25,26,27,28,29,30,31,32].