A newly designed loop for en-masse anterior retraction - a finite element study

Objective : The present study was aimed to analyse the efficacy of specs loop, a newly designed closing loop. Materials and Methods : A finite element maxillary model for en-masse anterior retraction was made. The newly designed specs loop was tested with different preactivation bends (alpha-30 degree; beta-15 degree, 30 degree and 45 degree) and without preactivation bends. The horizontal and vertical forces and moments at both the alpha and beta nodes and overall moment to force ratio, range of crown tip, root tip and vertical movement of all the individual teeth, stress acting on the teeth and bone were calculated for each group for a horizontal activation of 3 mm using Abaqus software. Results : Stress acting on the teeth and bone decreased with increasing beta bend. Moment-to-force (M/F) ratio acting on the anterior teeth was approximately 10:1 with preactivation bends of alpha 30 degrees and beta degrees 15, 30 and 45 degrees whereas the M/F ratio was only 2:1 without the preactivation bends. With increasing beta bend, distal crown tip of the teeth and the extrusive movement of the posteriors increased while the extrusive movements of the anterior decreased. Conclusion : The specs loop with preactivation bends can be efficiently used for en-masse anterior retraction.