Force Delivery From Various Forms of Nickel-titanium Preformed Orthodontic Archwires

Objectives: To compare the magnitude and direction of the force delivered to each tooth in the mandibular dental arch by various forms of light round nickel-titanium (NiTi) preformed orthodontic archwires
Methods: Thirty-four types of commercially available 0.016-in round NiTi preformed archwires from 12 manufactures were selected and classified by cluster analysis into Small, Medium, and Large groups according to the inter-first molar widths. Sets of brackets and three-dimensional force sensors were fixed at each tooth position of the mean mandibular dental arch based on an analysis of 30 adult non-orthodontic normal subjects (15 females, 15 males). The archwires were individually ligated to the brackets from the central incisors to the first molars in a randomized order using conventional elastic modules. The magnitude and direction (perpendicular to the dental arch in the horizontal plane) of forces at 6 brackets from the right central incisor to the right first molar were recorded. The median force magnitude at each bracket for each archwire group was calculated and these values were compared among the three groups using the Kruskal-Wallis test and a post-hoc test with Bonferroni correction (P < 0.05).

Results: Significant differences in the force magnitude were observed among the three groups for all brackets, except the lateral incisor (P < 0.05). The force magnitude delivered by the Large group of archwires was significantly greater than the force delivered by the other groups in the lingual direction at the first premolar and first molar and in the opposite direction at the remaining teeth (P < 0.05).


Conclusions: Significant variation in the magnitude and direction of the orthodontic force delivered to each bracket in the mandibular dental arch, except the lateral incisor, was observed among the three groups of light round NiTi preformed archwires.