Salivary Cobalt, Nickel, Chromium and Titanium After Fixed Orthodontic Appliance Removal: A 3-Month Pilot Longitudinal Study

Objective: Our objective was to determine the salivary levels of cobalt, nickel, chromium, and titanium ions at the end of fixed orthodontic treatment and during the post-removal period (1 and 3 months after removal of the fixed appliance). Methods: This pilot longitudinal study included fifteen individuals (10 females and 5 males). Five milliliters of saliva was collected at three time points: T1 (before withdrawal of orthodontic appliances), T2 (one month post-withdrawal), and T3 (three months post-withdrawal). The concentrations of nickel (Ni), titanium (Ti), chromium (Cr), and cobalt (Co) in the samples were analyzed using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). All samples were analyzed in triplicate. The data were analyzed by repeated-measures ANOVA, and differences were considered significant if the p-value was ≤0.05. Results: The concentrations of Co, Cr, and Ti at the three time points were low and decreased after the removal of the orthodontic appliance, while Ni showed an increase at T3. Co and Ni showed significant differences between T3 and T1 (p = 0.016 and p = 0.029, respectively). There was also significantly increased Ni ion release at T3 compared to T2 (p = 0.010). The Cr and Ti levels at all three time points were significantly different (Cr: p = 0.001; Ti: p = 0.001 and p = 0.005). Conclusions: The levels of cobalt, chromium, and titanium in saliva decreased after removal of the orthodontic appliance, whereas nickel increased at T3. However, the levels were below the mean dietary intake levels; therefore, these concentrations can be considered non-toxic. This study has limitations that should be considered when interpreting the results.