Predictable method to deliver physiologic force for extrusion of palatally impacted maxillary canines

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IntroductionOrthodontic treatment of palatally impacted maxillary canines raises many difficulties; to minimize complications, careful planning of orthodontic extrusion and the use of physiologic force are crucial. The aim of this study was to quantitatively evaluate a simple and reproducible system for orthodontic extrusion of impacted canines that can provide the correct amount of force.MethodsTen specimens were constructed, consisting of a cantilever made with a 0.6-mm or 0.7-mm stainless steel wire modeled around a transpalatal bar with 3, 5, or 7 loops in the shape of a helical torsion spring. A mechanical testing machine was used to measure the force produced by the cantilever at 3, 6, 9, 12, and 15 mm of activation.ResultsThe force values ranged from 1.24 ± 0.13 N for the 0.7-mm wire with 3 loops to 0.48 ± 0.04 N for the 0.6-mm wire with 7 loops. The forces measured for the 0.6-mm wire with 3 loops and the 0.7-mm wire with 7 loops were similar at 15 mm of deflection.ConclusionsThe proposed system has a simple and robust design, is easy to construct and manage, and can provide the desired amount of force by changing the wire diameter and number of loops.Graphical abstractHighlightsFew studies have evaluated the force used by devices for maxillary canine extrusion.The appliance uses a stainless steel cantilever arm with a helical torsion spring.Changing the wire diameter and the number of loops produces different forces.Physiologic force values below the recommended 0.6 N can be predictably reached.This device is simple, economical, easy to manage, stiff, and resistant to breakage.

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