Methods: 30 patients were enrolled in this experiment. Saliva sample collection was performed at four time points: T1, before insertion of orthodontic appliances; T2, 3 months after the initiation of orthodontic treatment, before induction of stress; T3, 15 min following the induction of stress by Trier Social Stress Test; T4, 30 min following the induction of stress. Ion content was measured by atomic absorption Spectrophotometry. The obtained data were analyzed by repeated-measures analysis of variance (ANOVA) and post hoc Bonferroni test.
Results: The mean amount of salivary nickel increased from 11.88 ± 5.11 μg/L at T1 to 14.11 ± 5.31 μg/L at T4. This increase was found significant only at T4 compared to T1. The average salivary chromium content changed from 4.09 ± 2.33 μg/L at T1 to 5.10 ± 3.28 μg/L at T4. None of the differences was significant for chromium.
Conclusions: In this study induction of stress led to a significant increase in nickel release from orthodontic appliances into saliva. The salivary chromium content, however, was not significantly altered, yet gradually increased.