Methods: GCF, from mesiobuccal and distopalatal locations of maxillary canine teeth, was collected on Periopaper™ strips for 30s from volunteers (n=21) at: baseline, before appliance placement and tooth extraction (B); three months into orthodontic treatment and post-tooth extraction, having followed a normal archwire progression (T1); at four hours (T2); 1 week (T3); and 6 weeks after a distalising force had been applied to the maxillary canine teeth (T4). GCF volumes were recorded and proteins eluted into sterile water and stored at -80°C. Cytokines (GM-CSF, interferon-&gamma, IL-1&beta, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10 and TNF&alpha), tissue (MMP9, TIMP1 & 2) and bone metabolism (RANKL and OPG) biomarkers were measured using muliplex assays in a Luminex 200™.
Results: The tension site at the maxillary canines showed increases in IL-1&beta, IL-8, TNF&alpha, MMP9 and TIMPs 1&2 across time points T2-T4, whereas the compression site for these teeth showed increases in IL-1&beta and IL-8 only at T2, MMP9 at T3 and T4 and RANKL at T4. GCF volume increased from T2 to T4 but plaque or bleeding on probing did not increase over this time. More biomarkers were consistently detected at sites of tension than compression. Other biomarkers were below assay detection limits.
Conclusions: These data demonstrate that high levels of GCF pro-inflammatory cytokines and tissue and bone metabolism biomarkers are associated with orthodontic force application and highest levels arise at sites of tension rather than compression. Elevated levels were evident at 4h but continued for longer periods of time (up to 6weeks).