Force Delivery From Different Forms of Nickel-titanium Alloy Preformed Archwires

Objectives: The magnitude and direction of the force from nickel-titanium preformed archwires to the brackets and teeth in the dental arch has not been fully clarified. Therefore, this study compared the magnitude and direction of the force from 2 nickel-titanium alloy preformed round archwires with different forms to the lower brackets in a simulation of the mandibular dental arch.
Methods: A multi-sensor measuring system was used to simultaneously measure the magnitude and direction of forces at brackets on 7 teeth. The system consists of brackets welded to the metal blocks aligned to the average shape of the Japanese mandibular dental arch, to which seven six-axis force sensors were connected from the right lateral incisor to the left second premolar block. The force in the horizontal direction (Fx) was recorded with positive (lingual direction) or negative (labio/buccal direction) values. Nickel-titanium alloy preformed archwires with a diameter of 0.016 inch with two different archforms (tapered and square) were ligated to the brackets using elastic modules. Fx at the 7 brackets were measured using 10 new archwires for each archform. The force direction for each bracket was analyzed and the mean forces (mN) were compared between the two archwire forms using the Mann–Whitney U test (p<0.05).
Results: Significant differences between the 2 archwire forms were observed for the force magnitude at the central incisors, lateral incisors and left canine (p <0.05). The tapered archwire form produced significantly larger labial force than the square form at the central incisors bracket (p <0.01), whereas, it produced significantly larger lingual force at the lateral incisors and left canine bracket (p<0.05).
Conclusions: The magnitude of the force at the central incisors, lateral incisors and left canine brackets may be affected by the use of different archwire forms.