Somatosensory, inflammatory and pain evaluation during Orthodontic Treatment

Experimental tooth movement has been shown to induce inflammation and release of chemical mediators. Inflammation can also alter nerve function that can be measured with Quantitative Sensory Testing (QST). Various authors have studied orthodontic pain and the different factors that modify it. But, to our knowledge none studied a possible individual endogenous analgesia effect on orthodontic induced-pain. The aim of the present study was to investigate the impact of orthodontic separator and short-term fixed orthodontic appliance on the somatosensory function and gingival cervicular fluid (GCF) levels of IL-1, IL-8, IL-6 and TNF-. Thirty patients were evaluated as follow: baseline, 24h-after elastomeric separator (24h-aES), 24h and 1 month after bonding the fixed appliance (aBFA) at maxillary and mandibular arch. The outcome variables were: self-reported pain, QSTs (current perception threshold, cold detection threshold, warm detection threshold, mechanical detection threshold, mechanical supra threshold and wind-up ratio, CPM and sample from the GCF in order to assess cytokines profile (IL-1, IL-8, IL-6 and TNF-). ANOVA and Tukeys post hoc analyses were performed (a = 5%). The participants were divided in two groups: G1) RESPONDERS (more than 10% decrease in WUR); G2) NON-RESPONDERS (not show more than 10% decrease in WUR). T-test for independent sample was performed. A Bonferroni correction lowered the significance level to 0.1% (p = 0.001) as the cut-off point to establish the statistical significance for the mean difference between CPM responders and non-responders. Patients were less sensitive to pin prick pain (MST) at 24h (p<0.020) and 1month-aBFA (p<0.002) when compared to baseline. Significant increases in IL-6 levels were observed 24h-aBFA (p<0.023) and in IL-1 (p<0.001) and TNF- (p<0.026) levels at 1 month-aBFA when compared to baseline values (p<0.023). There was no significant difference in somatosensory function, pain report and GCF cytokines when compared between G1 and G2. In conclusion, orthodontic-induced inflammation may have a modality specific effect on somatosensory function of the trigeminal system. In addition, elastic separators seem not an ideal model to study possible inflammatory changes following orthodontic tooth movement. Moreover, CPM efficiency may not significantly influence somatosensory function, pain intensity or released of inflammatory cytokines following orthodontic tooth movement up to 1 month. However, remained to be confirmed and further investigations are required in intraoral somatosensory assessment. (AU)