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

The objective of this study was to test the hypothesis that toxic metallic ions in silver solder used in orthodontics are released into saliva.

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.

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 μg/L) and the lowest mean for zinc (0.07 μg/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.

Great amounts of these ions were released, with the highest concentrations immediately after placement of the appliance.