In-vivo evaluation of salivary nickel and chromium levels in conventional and self-ligating brackets

Abstract

Our objective was to evaluate and compare the salivary levels of nickel and chromium before and 1, 7, and 30 days after placement of conventional and self-ligating appliance systems. Twenty women were randomly divided into 2 groups. Patients in group 1 had conventional brackets bonded to their teeth; in group 2, self-ligating brackets were bonded. Four samples of unstimulated saliva were collected from each patient 1 hour before placement of the fixed appliance, and 1, 7, and 30 days after placement of the appliance. The chemical analyses for nickel and chromium levels were performed with an atomic absorption spectrometer (PerkinElmer, Shelton, Conn). Two-way repeated measures analysis of variance by ranks (Friedman test) were used to test the statistical significance of differences in the concentrations of nickel and chromium before and after placement of the appliances. Post-hoc pair-wise comparisons among groups of the same element were calculated by using the Wilcoxon signed rank test. A value of P≤0.05 was considered significant. Nickel and chromium released into saliva from conventional and self-ligating brackets progressively increased from days 1 to 7 and then decreased at day 30. Nickel release was less, and chromium release was greater in the conventional bracket group. Both the conventional and the self-ligating brackets did not seem to affect significantly the nickel and chromium concentrations in saliva during the first month of treatment.