Effect of applied moment on resistance to sliding among esthetic self-ligating brackets

Objective: To determine the effect of mode of ligation and bracket material on resistance to sliding (RS) by comparing various esthetic brackets of conventionally ligated and self-ligating (SL) designs under an increasing applied moment in the second-order dimension. Materials and Methods: Eight different commercially available esthetic brackets of SL and conventional elastomeric-ligated (CL) designs were mounted on a testing apparatus to simulate canine retraction using sliding mechanics and the application of a moment on 0.019″×0.025″ stainless steel archwire. The samples examined were the CL brackets Clarity™, Inspire Ice™, SpiritMB™, and Mystique™, and the SL brackets ClaritySL™, In-OvationC™, In-OvationR™, and Smartclip™. The RS at calculated moments of 2000 g-mm and 4000 g-mm was determined and compared between the various brackets. Descriptive measures and one-way analysis of variance were used to calculate means and statistical differences among the bracket types. Results: The CL monocrystalline bracket displayed significantly greater (P < .05) RS than all other brackets tested. Among the other brackets, the range of RS values was 145.8–191.7 g and 291.9–389.2 g at moments of 2000 g-mm and 4000 g-mm, respectfully, though these differences were not significant (P < .05). All brackets tested displayed greater levels of RS (P < .05) at 4000 g-mm than at 2000 g-mm. Conclusion: With the exception of the CL monocrystalline bracket, all brackets displayed comparable amounts of RS regardless of mode of ligation or bracket slot material.