Evaluation of Salivary Nickel and Chromium Levels in Two Different Bracket and Ligation Types

Objectives: The aim of this study was to evaluate the levels of nickel and chromium released into saliva by self-ligating brackets and conventional brackets ligated with elastomeric ligatures.
Methods: Twenty-eight orthodontic patients (mean age 13.9 ± 1.8 years) were included in this study. The patients were randomly assigned to two groups of 14 each. All patients had brackets bonded to maxillary and mandibular teeth (central tooth to first molar tooth). The first group had conventional edgewise brackets (Dentaurum equilibrium® 2, Pforzheim, Germany) bonded to their teeth, while the second group had self-ligating brackets (Damon Q; Ormco, Orange, Calif) bonded to their teeth. The conventional edgewise brackets were ligated with elastomeric ligatures (Versa-Tie^TM Ligature Tie, G&H, Franklin, USA). A 0.016-in nickel titanium archwire was inserted for the initial leveling. During the study period, no additional materials, coil springs, or stainless steel ligature wires, which contain metals, were used. Four unstimulated salivary samples were obtained from each patient before orthodontic treatment, 2 weeks later and prior to placement of Ni-Ti archwires, 2 weeks after wire placement, and 4 weeks after wire placement. The salivary samples were analyzed using inductively coupled plasma mass spectrometry (ICP-MS). Statistically significant differences for salivary Ni and Cr levels among the two groups were determined using the Mann–Whitney U test. The Friedman test was used for salivary Ni and Cr levels to determine the differences in the means within each group. The significance for all statistical tests was predetermined at P<.05. Differences in the mean changes in salivary levels of Ni and Cr within each group were determined using the Wilcoxon signed rank test.
Results: No statistically significant differences in levels of salivary Ni and Cr were found between self-ligating brackets and conventional brackets (P > .05). Ni and Cr levels at T1, T2, and T3 were significantly increased when compared with T0 in both groups (P < .05).
Conclusions: No differences existed between self-ligating brackets and conventional brackets ligated with elastomeric ligatures in terms of salivary levels of nickel and chromium.