BACKGROUND: Heat-activated nickel-titanium (HANT) wire is a new type of arch wire in orthodontic treatment, characterizing by well memory alloy ability and uneasily deformation. However, environmental temperature may affect its performance.OBJECTIVE: To compare the effects of HANT and common nickel-titanium wire in clinical application.METHODS: A total of 80 patients who have accepted and finished orthodontic treatment in the First Affiliated Hospital of Sun,Yat-sen University from July 2006 to November 2008 were randomly divided into two groups. The common group was treated with common arch wire in aligning and leveling stages, while the HANT group was treated using HANT in aligning and leveling stages. Tooth extracted cases were matched to non-tooth extracted cases. Indicators, such as time span for alignment, total treating time, times for wire breaking, times for bracket shedding, and times for return visits, were measured.RESULTS AND CONCLUSION: There was significant difference in treating time and times for wire breaking between the two groups (P < 0.05), but there was no significant difference in the times for bracket shedding. Anaphylactic response, toxic reaction,and other adverse reactions were not observed in the HANT group. Therefore, HANT wire can simplify orthodontic operation,shorten operation time beside the chair, save the total treating time, and reduce chances of shedding brackets and breaking wires.