MMP8 and Peri-Implantitis: Therefore, it is of interest to evaluate the diagnostic efficacy of salivary biomarkers-interleukin-1β (IL-1β), matrix metalloproteinase-8 (MMP-8) and tumour necrosis factor-alpha (TNF-α)-by comparing their concentrations in patients with healthy peri-implant tissues and those with peri-implantitis.