The biomechanical differences between labial and lingual constriction arch wire

Objective: Orthodontists use many types of arch wires and have to know the biomechanics of each arch wire to use them effectively. However, the force systems and effects produced from arch wires still are not completely known. The purpose of this study was to clarify the biomechanics of constriction ach wires from the labial and lingual sides. Methods: A three-dimensional model of human maxilla fabricated using different birefringent materials to simulate bone and teeth. The test model was made by using PL-2 and silicon impression material for bone and periodontal membrane simulants. The upper arch model for anterior teeth retraction was fabricated with labial and lingual constriction arch wires. Digital image correlation method was employed for analysis of tooth displacement. Results: The results were that the canine was rotated distally and posterior teeth were rotated mesially on labial arch wire model. On the other hand, the canine showed parallel displacement on lingual arch wire model and no distinguished rotation at the posterior teeth. Conclusions: By using digital image correlation method, the biomechanics of constriction ach wires from the labial and lingual sides were clarified. It was suggested the differences between the labial and lingual results were caused mainly by the bracket position from the center of resistance.