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.
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.