Analytical study for prediction of stress distribution on orthodontic archwire considering short-term stress loss

This article proposes a method to predict the stress distributions on orthodontic archwires by considering the short-term stress losses. First, finite element (FE) analysis and numerical analysis using stress-loss formulations were performed. The FE models of the upper teeth and archwire were generated, and the initial stresses along the archwire were predicted from the FE model. The initial stresses on the wire were released in a relatively short amount of time due to shortening of the teeth, and slip and friction between the wire and brackets. Therefore, the formulations for the short-term stress losses were adopted from prestressed concrete design techniques and used to calculate the wire stress releases. To validate, loading tests and image processing were conducted, and the stresses were calculated from the deformations and curvatures of the loaded wire images. FE analyses without considering the stress losses predicted the stress distributions are unrealistically large; hence, including losses from elastic shortening, anchorage slip, and friction area could reduce the initial stresses by 16-34%. Comparing the average wire stress from FE analysis with image processing, a difference of only 0.82% was noted, which validates the method for predicting stress distribution using FE analysis and the method for stress loss calculations.