Pain and discomfort experienced after placement of a conventional or a superelastic NiTi aligning archwire

Two nickel-titanium archwire types commonly used for initial tooth alignment were compared with regard to the pain/discomfort patients experience during the initial phase of tooth movement. The two archwires used were a superelastic nickel-titanium alloy, 0.014 inch Sentalloy, Light (GAC International Inc. Central Islip, NY, USA) and a 0.014 inch Nitinol (unitek, Monrovia, CA, USA), a conventional nickel-titanium aligning archwire.One hundred and twenty-eight consecutive patients attending an orthodontic university clinic and 2 private practices for routine placement of a fixed appliance were randomly assigned one of these 2 initial archwires. Assessments of pain/discomfort were made daily by means of a 100 mm visual analog scale (VAS) over the first 7-day period after bonding. On the first day, recordings were made every hour for the first 11 hours.The results showed that the level of discomfort increased continuously every hour after the insertion of either a Sentalloy or a Nitinol as first archwires, with a peak in the first night, remaining high on the second day and decreasing thereafter to baseline level after 7 days. During the first 10 hours it was apparent that the pain/discomfort experienced after placement of a Sentalloy was less than that found with the Nitinol archwire, although a significant difference could be found at 4 hours only. No significant gender-specific differences were found in either archwire group. A significant difference between the upper and lower dental arches was observed during the first 11 hours after placement of either a Sentalloy or a Nitinol archwire, with the lower arch having the higher pain experience.