Biomechanical Analysis of Extraction Space Closure with Various Loop Springs Incorporated into an Archwire

The purpose of this study was to compare the mechanical efficacies of the various loop springs in the extraction space closure. The long-term movement of the teeth was simulated by the finite element method. It was assumed that the tooth moved in the same direction as the initial movement due to elastic deformation of the periodontal ligament. After the spring was activated, the initial movement was calculated, and then the alveolar socket was moved. By repeating this calculation, the teeth moved by accumulating the initial movement. The anterior teeth first tipped lingually and then became upright; thereby, the extraction space was closed for a fixed distance. In all cases, the gable bends were effective in increasing the closing speed. A higher loop increased the closing distance. When the helical loop was replaced with the vertical loop, the closing distance decreased. A spring made of thick wire increased the closing speed but decreased the closing distance. No spring increased both the closing distance and the closing speed at the same time. In clinical settings, an appropriate spring should be selected for each case by giving priority to either the closing distance or speed