MMP8 and periodontitis: A statistical analysis revealed that MMP-8 level in PISF was significantly higher not only than in periodontally healthy subjects (P = 0.0099) but also than in patients with mild periodontitis (P = 0.0321), moderate periodontitis (P = 0.0489), and, which should be pointed out, with severe periodontitis (P = 0.0255).