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Chronic periodontitis is a chronic inflammatory disease that results in the destruction of the supporting connective and osseous tissues of the teeth 1) . A group of enzymes thought to be important in this degenerative process is the matrix metalloproteinase familly (MMPs) 2,3) . Gingival fibroblasts, keratinocytes, resident macrophages and polymorphonuclear leukocytes (PMNLs) are capable of expressing MMP-1, MMP-2, MMP-3, MMP-8 and MMP-9 2) . Collagen is the major extracellular matrix component of gingiva and thus is implicated in pathological states such as periodontitis. It is now recognized that during active periodontitis, degradation of gingival tissue (mainly collagen) is due in part to matrix metalloproteinases (MMPs) expressed in situ by inflammatory cells (monocyes, macrophages, lymphocytes, PMNLs) and resident cells (fibroblasts, epithelial cells, and endothelial cells) 3) .1) Matrix metalloproteinases (MMPs) are a family of metal dependent proteolytic enzymes that mediate the degeneration of extracellular matrix and basement membranes 4,5) . MMPs are composed of at least 23 related zinc or calcium dependent endopeptidases that are able to degrade extracellular matrix proteins at a pH close to neutral 6) . MMPs are secreted as inactive form (proenzyme) and are activated in the extracellular compartment or in the vicinity of the cell membranes by other MMPs or serine proteinases through peptide cleavage. Three major types of MMPs have been identified: the collagenases degrade interstital collagen types I, II and III; the gelatinases (also called type IV collagenases) degrade type IV collagen and denatured interstitial collagens; and the stro