Release of toxic ions from silver solder used in orthodontics: An in-situ evaluation

Introduction: The objective of this study was to test the hypothesis that toxic metallic ions in silver solder used in orthodontics are released into saliva. Methods: The sample included 60 children, 8 to 14 years of age, divided into 2 groups (n = 30 in each group): the control group and the study group (needing maxillary expansion with the hyrax appliance). For analysis of the release of metallic ions, saliva samples from each patient were collected at 6 times in both groups: before placement of the appliance and 10 minutes, 24 hours, and 7, 30, and 60 days after placement. The analysis of saliva was performed by atomic absorption spectrophotometry in a graphite oven to determine the concentrations of cadmium, copper, zinc, and silver ions. Statistical analyses were performed by the mixed model for repeated-measures covariance structure of the symmetrical component type, at P <0.05. Results: The ion concentrations in the control group had low values for cadmium, copper, and zinc (P >0.05); for silver ions, the values did not reach the detection limit. In the study group, all ions showed expressive concentrations at 10 minutes after placement of the appliance (P <0.001), with the highest mean for copper (70.60 mu g/L) and the lowest mean for zinc (0.07 mu g/L). Comparison between groups revealed significant differences for copper (all periods), zinc (10 minutes, 24 hours, 7 and 30 days), and for cadmium only at 10 minutes. Conclusions: Great amounts of these ions were released, with the highest concentrations immediately after placement of the appliance. (Am J Orthod Dentofacial Orthop 2011;140:177-81)