MMP2 and periodontitis: In periodontal tissue, when there is dental plaque stimulation and periodontal disease, the expression and activity of matrix metalloproteinases (MMPs) are pathologically increased [26], especially MMP-2, which is a key enzyme involved in connective tissue degradation and tissue remodeling that is overexpressed in gingival crevicular fluid, gingival tissue, and saliva samples from patients with chronic periodontitis [27].