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Incorporation of metal and color alteration of enamel in the presence of orthodontic appliances.

OBJECTIVE
To test the null hypothesis that it is not possible to incorporate metal ions arising from orthodontic appliance corrosion into tooth enamel with resulting tooth color change.


MATERIALS AND METHODS
This in vitro study used atomic absorption spectrophotometry to evaluate the presence of nickel, chromium, and iron ions in tooth enamel in three groups: a group submitted to cyclic demineralization and remineralization processes with solutions in which orthodontic appliances were previously immersed and corroded, releasing metallic ions; a control group; and another group, submitted to cycling only, without the presence of orthodontic appliances. The influence of the incorporation of these metals on a possible alteration in color was measured with a portable digital spectrophotometer using the CIE LAB system.


RESULTS
At the end of the experiment, a significantly higher concentration of chromium and nickel (P < .05) was found in the group in which corrosion was present, and in this group, there was significantly greater color alteration (P ≤ .001).


CONCLUSIONS
There was chromium and nickel incorporation into enamel and tooth color change when corrosion of orthodontic appliances was associated with cycling process. The null hypothesis is rejected.