Matrix metalloproteinases and tissue inhibitors of metalloproteinases in gingival crevicular fluid during orthodontic tooth movement

Orthodontic tooth movement requires extensive re-modelling of the periodontium. Matrix metalloproteinases (MMPs) degrade the extracellular matrix during re-modelling, while their activity is regulated by the tissue inhibitors of metalloproteinases (TIMPs). The aim of this study was to investigate differences in MMP and TIMP levels in the gingival crevicular fluid (GCF) at the resorption and apposition sides of orthodontically moved teeth, and to compare these with control teeth. GCF samples were collected from eight orthodontic patients wearing fixed appliances with superelastic nickel-titanium coil springs. The samples were analysed by gelatin zymography, which allows detection of both active and latent MMPs, and reverse zymography for analysis of TIMPs. Western blotting was performed to confirm the identity of MMPs. The data were analysed using either the one-way analysis of variance or the Kruskal-Wallis test. In general, higher levels of MMPs and TIMPs were found at both the resorption and apposition sides compared with the control teeth. Remarkably, partially active MMP-1 was found in GCF from both the resorption and the apposition side but was barely present at the control teeth. TIMP-1 was strongly increased at the apposition side. Gelatinases were mainly present at the resorption side, while gelatinolytic fragments were exclusively detected at the apposition side. MMP-9, which is known to be involved in bone degradation, and a 48 kDa gelatinase were increased at the resorption side. The small increase in TIMP-1 at the resorption side might stimulate bone resorption, whereas the large increase at the apposition side reduces bone resorption. The analysis of MMPs and TIMPs may contribute to the improvement of orthodontic treatment regimens.