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Our aim in this study was to compare conventional, active self-ligating and passive self-ligating mechanisms using first order archwire deflections. A cantilever and three point bend model were used to assess degree of bracket play, deactivation force, and superelastic range. Methods: We studied five different bracket types: victoryTM( 3M-Unitek, St. Paul, MN), smartClipTM( 3M-Unitek, St. Paul, MN), Damon hYTM( ~ rmc oG, lendora, CA), CarriereTM( Ortho Organizers, Carlsbad, CA) and In- Ovation R~~ (GAC Intl., Bohemia, NY). These brackets were tested with round superelastic nickel titanium wires varying in diameter: 0.014", 0.016", 0.018" and 0.020" (Ultimate Wireforms Inc., Bristol, CT). Using a mechanical testing apparatus with custom fixture we recorded the load-deflection curve generated by the deflected archwire over a span of 4mm. The wire was deflected at a rate of 10mmImin and measurements were taken at a rate of 20Hz. Data was compared and analyzed using a single factor ANOVA with the bracket type as the discriminating variable. Group differences were further analyzed using post-hoc T-tests (a = 0.01). Results: Bracket play was significant for both wire diameters (p50.01). The 0.014" wire showed significantly less play with the Victory and In-Ovation R brackets when compared to the passive self ligating brackets (PSLBs). For PSLBs, the Smartclip bracket had significantly less bracket play than the Damon MX and Carriere, which were not significantly different. Both the ligation mechanism and the archwire diameter had a significant effect on deactivation load. Victory and In-Ovation R brackets provided a measurable deactivation load at lmm, while the PSLBs provided no such force with the 0.014" wire. During the cantilever test, PSLBs produced the lowest deactivation forces for all wires tested. The three point bend test showed similar results with small diameter wires. As the degree of deflection and archwire diameter increased, the PSLBs displayed reduced deactivation forces, which are related to significant binding and increased sliding frictional resistance. The superelastic range varied significantly for the various bracket types (p_<0.01). Victory provided the largest superelastic range for all wires except the 0.020". Of the SLBs tested, In-Ovation R displayed the larger superelastic range. The 0.014," test showed a significant difference in superelastic range for all brackets except the Damon MX and Carriere, which were not significantly different from each other. Conclusions: The type of ligation has a significant effect on the degree of bracket play, force of deactivation and superelastic range. These factors influence the clinician's ability to achieve full first-order correction and to maintain light, continuous forces over a wide range of activation. The clinician should consider the degree of correction needed and type of ligation when selecting the appropriate alignment wire.

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