MMP9 and periodontitis: These include tetraspanins (CD9 and CD81), soluble urokinase plasminogen activator receptor (suPAR), galectin-1, matrix metalloproteinase 9 (MMP-9), S100 calcium-binding protein A8 (S100A8), lactate dehydrogenase (LDH), aspartate aminotransferase (AST), and cytokines (IL-1β, IL-6, and TNF-α), which reflect the complex pathophysiology of periodontitis [15,16].