Correlation Between the Force From Orthodontic Archwires and Archwire Form

Objectives: To determine whether a relationship exists between the force delivered by various forms of stainless steel (SS) orthodontic preformed archwires to each bracket from the central incisors to the first molars and the archwire form that is expressed by the ratio of the archwire widths.
Methods: The ratio of the inter-canine width to the inter-molar width was calculated for 20 commercially available .016-in round SS preformed archwires. Sets of brackets and three-dimensional force sensors were fixed at each tooth position on a mandibular dental arch model created based on the mean measurements of 30 adult non-orthodontic normal subjects (15 females and 15 males). Each .016-in round SS preformed archwire was ligated to the brackets from the central incisors to the first molars in random order. The magnitude of the force delivered by each archwire to the six brackets from the right central incisor to the right first molar was recorded. Spearman’s rank correlation coefficients were calculated to evaluate the relationships between the magnitude of the force at each bracket and the ratio of the widths of the 20 commercially available archwires.
Results: Significant correlations were found between the ratio of the widths and the magnitude of force at the right first premolar (rs = -0.639, P = 0.02), second premolar (rs = 0.488, P = 0.03), and first molar bracket (rs = -0.548, P = 0.01). However, no significant correlations were found between the ratio of the widths and the magnitude of force at the anterior brackets.
Conclusions: These results suggest that the magnitude of force delivered by 20 types of commercially available .016-in round SS preformed archwires to the posterior brackets is related to the archwire form expressed by the ratio of the inter-canine width to the inter-molar width.