In addition to typical bone collagen matrix degradation, MMP-13 regulates bone resorption in periodontal disease through osteoclast differentiation (by inactivating galectin-3, an inhibitor of osteoclastogenesis) and osteoclast activation (by activating osteoclast-secreted pro-MMP-9 and favoring RANKL and TGF-β1 signaling). This evidence concerns the gene MMP9 and periodontal disorder.