RESUMEN
<p><b>OBJECTIVE</b>To observe the color changes of nickel-titanium (Ni-Ti) orthodontic wires induced by fluoride.</p><p><b>METHODS</b>Each 40 samples of 4 kinds of nickel-titanium orthodontic wires (IMD, SL, TP, YY) were put into artificial saliva with sodium fluoride at different F concentrations (0.05%, 0.10%, 0.15%) and artificial saliva, separately. Dislodged the species and immersed them into artificial saliva with sodium fluoride for 3 minutes, then washed them with deionized water, and put back to artificial saliva, this course should be repeated 3 times per day. The whole immersion test lasted for 28 days. The color and micro-morphous changing were observed.</p><p><b>RESULTS</b>The color changes came to be more serious as the F- concentration growing (P < 0.05). At the same F- concentration, the color changes of IMD and YY were higher than SL and YP (P < 0.01), while there were no significant difference between IMD and YY, SL and TP (P > 0.05).</p><p><b>CONCLUSION</b>Fluoride can change the color of Ni-Ti wire. Different Ni-Ti wires get different changes at the same F- concentration.</p>