Читать книгу Biological Mechanisms of Tooth Movement - Группа авторов - Страница 65

These agents are zinc‐ion‐dependent proteolytic enzymes, produced by a wide variety of cells during developmental processes, inflammatory diseases, degenerative articular diseases, tumor invasion, and wound healing. These enzymes are classified into several subgroups, i.e., collagenases (MMP‐1, 8, and 13), gelatinases (MMP‐2 and 9), stromelysins, membrane‐type MMPs, and other subfamilies. Most of the MMPs are produced as pro‐enzymes, cleaved at the specific site to become a mature form, and then secreted and activated in the presence of zinc and calcium ions. The activation of MMPs is also regulated by a group of endogenous proteins named tissue inhibitors of metalloproteinases (TIMPs), which are each capable of inhibiting almost every member of the MMP family in a nonspecific way. The MMPs/TIMPs ratio is supposed to determine the turnover rate of periodontal tissues, and consequently to influence the outcome of OTM (Garlet et al., 2007).

In vivo studies demonstrated that MMP‐1, 2, 3, 8, 9, and 13 were expressed in the PDL and alveolar bone during OTM (Takahashi et al., 2003, 2006; Garlet et al., 2007; Leonardi et al., 2007). Further, in vitro studies also demonstrated that the expression of MMP‐1 and MMP‐2 mRNA in human PDL cells was detected after exposure to mechanical stress (He et al., 2004; Redlich et al., 2004). When MMPs and TIMPs were investigated simultaneously in PDL under orthodontic forces, higher MMP‐1 levels were found in the compression than in the tension side, while TIMP‐1 levels were upregulated in the tension area (Garlet et al., 2007), suggesting that there exists a differential pattern of expression providing distinct microenvironments favorable for extracellular matrix synthesis or degradation. The role of the MMP system in the regulation of OTM was experimentally confirmed, since the inhibition of MMPs activity with chemically modified tetracyclines, or by anti‐inflammatory or immunosuppressive drugs (such as potassium diclofenac and dexamethasone), inhibited experimental tooth movement in rats (Bildt et al., 2007; Molina Da Silva et al., 2017).