Controlled space closure with a statically determinate retraction system.

We designed a variant of a cantilever spring, the statically determinate retraction system, and studied its mechanical characteristics. This novel system consisted of a single-force cantilever arm made of 0.017 x 0.025-inch titanium molybdenum alloy wire for active retraction and a passive rigid stabilizing unit. Since the active component for space closure is a cantilever, it is simple to measure the force system of the spring with a force gauge (ie, the system is a statically determinate system). A torque tester apparatus was used to examine the property of this retraction spring with a helix at the posterior and a simple bend at the anterior. Both a standard shape and modified shapes of the spring were studied. At full activation, the standard spring delivered 163 g with a load-deflection rate of six g/mm. When the magnitude of the anterior bend of the spring was increased, the horizontal component of the force increased more than the vertical component. In contrast, when the posterior bend of the spring increased, the vertical component of the force increased more than the horizontal component. A clinical case presented here clearly demonstrates the versatility and applicability of the spring.