This study evaluated the gene expression of IL-1ß, IL-6, TNF-α, MMP-1, MMP-2, MMP-8, MMP-9, TIMP-1, and TIMP-2 in the gingival tissue of individuals with periodontitis or peri-implantitis compared to individuals without periodontal or peri-implant disease. The gene discussed is MMP9; the disease is periodontitis.