Comparison of ion release from new and recycled orthodontic brackets

Bracket corrosion can occur in the oral environment. The purpose of this st udy was to compare the release of metal ions from new and recycled brackets in artificial saliva and buffers with different pH values over a 12-week i mmersion period. The brackets were divided into 2 groups: new and recycled. The recycled bracket bases were coated with adhesive and the brackets were heat treated. Nickel, chromium, iron, and manganese ions were detected by atomic absorption. The surface characteristics of the brackets were examine d by energy dispersive radiographic analysis. The results were as follows: (1) Recycled brackets released more ions than did the new brackets. (2) Gre ater amounts of nickel, iron, and manganese ions were released in artificia l saliva than in the other buffers tested. (3) ion release from brackets in a pH 4 buffer was greater than that observed in pH 7 or pH 10 buffers. (4) The total amount of ion release increased with time. (5) After a 12-week i mmersion, the total ion release averaged over the period did not exceed the recommended daily intake.