| Introduction. Orthodontic tooth movement requires the precise coordination of a multitude of biological factors in order for proper bone remodeling to occur. Cytokines, such as Interleukin-6 (IL-6), play a critical role in the communication necessary for both bone resorption and bone apposition. IL-6 reacts with receptor proteins, such as soluble IL-6 receptor (sIL-6R), on target cells in order to transmit signals important to both osteoclast and osteoblast activities. Soluble glycoprotein 130 (sgp130), on the other hand, acts as a natural inhibitor to IL-6 activity. The purpose of this investigation was to evaluate the levels of IL-6, sIL-6R, and sgp130 in the gingival crevicular fluid (GCF) of human teeth undergoing orthodontic forces on both the tension and compression sides in the initial stages of orthodontic tooth movement. Methods. GCF samples were obtained from 9 healthy orthodontic patients [5 males, 4 females, age range 11 to 31 years (mean 17.445 years)] just prior to initial wire placement (0.012 or 0.014 Nickel Titanium archwire) with fixed orthodontic appliances. GCF samples were then collected 1, 6, and 24 hours after orthodontic force application. Patients returned in 5--7 weeks for a 2nd visit and orthodontic re-activation. GCF samples were again collected immediately before orthodontic activation, as well as 1, 6, and 24 hours after force application. Sampling sites included the mesiobuccal and distolingual of an experimental tooth, as well as the mesiobuccal of a control. GCF volumes were assessed with a Periotron 6000 (OraFlow, Smithtown, New York), while a Bradford assay was performed to obtain protein levels. Processing was carried out with a multiplex bead-based Luminex assay to detect IL-6, sgp130, and sIL-6R levels in the GCF samples. Results. GCF volumes were significantly higher in the experimental samples at both the initial (p=0.009) and recall visits (p=0.055). The greatest difference between GCF volumes for the experimental and control sites was after 6 hours of orthodontic activation (p=0.02). Relative to the control site, GCF IL-6 levels were significantly elevated for the mesiobuccal experimental site at 6 (p=0.001) and 24 hours (p=0.004) post-activation, whereas the IL-6 levels for the distobuccal experimental site were only elevated at 24 hours post-activation (p=0.034). GCF sgp130 levels were elevated for the mesiobuccal experimental site at 1, 6, and 24 hours post-activation relative to both the distobuccal experimental site (p=0.005, p=0.012, p=0.001) and the control site (p=0.005, p=0.001, p=0.000). Similarly, GCF sIL-6R levels were also elevated for the mesiobuccal experimental site at 1, 6, and 24 hours post-activation relative to both the distobuccal experimental site (p=0.035, p=0.029, p=0.001) and the control site (p=0.037, p=0.006, p=0.006). Conclusions. GCF volumes increase in a time-dependent fashion after orthodontic forces are applied to a tooth. Meanwhile, IL-6 levels in the GCF of orthodontically treated teeth increase earlier than previously reported. In the present study, IL-6 levels peaked at approximately 6 hours post-activation. Additionally, sgp130 and sIL-6R levels in the GCF are elevated throughout the first 24-hour post-activation period in orthodontic tooth movement. While there was a definitive difference in protein levels between opposing sides of the experimental teeth, further research is needed to differentiate the levels of IL-6, sgp130, and sIL-6R on the compression and tension sides during orthodontic tooth movement. |
