Evaluation of moment-force ratio of two different loops: A finite element study.

Biomechanics of space closure is an integral stage of orthodontic treatment wherein, the understanding of the mechanical system utilized for closing extraction space is critical. Loop mechanics is a more convenient method of space closure in that a known force system is delivered to the teeth and no friction involved. Two popular loops used for en-masse space closure are Double Keyhole loop and Continuous T-loop. However, they are biomechanical properties and their retraction efficiency has not been studied previously in literature. Therefore, the present study aimed to involve the moment-force ratio of Double Keyhole loop and Continuous T-loop for en-masse space closure with two different methods of activation using a finite element method. The resultant stress, displacement and moment-force ratio was calculated for two loops at 0, 15 and 30 degree gable bends at 1 mm activation using cinch back and ligature tie. Results show that there was no significant difference in the overall stress distribution and displacement of the teeth with both the loops. Nevertheless, the moment-force ratio achieved a desirable ratio of 8-10 and increased with increase in gable bend with both Double Keyhole loop and Continuous T-loop. Therefore the study conclusively proves that both the loops, though different in design and morphology was equally efficient for en-masse space closure producing bodily or translatory tooth movement without anchor loss in maximum anchorage cases