Moment-to-force characteristics of preactivated nickel-titanium and titanium-molybdenum alloy symmetrical T-loops

Autor: Michael V. Swain, Peter Herbison, Darnell Rose, Andrew N. Quick
Rok vydání: 2009
Předmět:
Zdroj: American Journal of Orthodontics and Dentofacial Orthopedics. 135:757-763
ISSN: 0889-5406
DOI: 10.1016/j.ajodo.2007.06.015
Popis: This in-vitro study investigated the loads (forces), moments, and moment-to-force ratios (M:F) generated during the activation and deactivation of T closing loops made of rectangular nickel-titanium (NiTi) and titanium-molybdenum alloy (TMA) wires incorporating either 0 degrees, 15 degrees, or 30 degrees of preactivation.T-loop designs were formed in the wires by using a standard template, and, for the NiTi alloys, a temperature of 510 degrees C for 9 minutes was used. Forces and moments of the T-loops were measured at 35.6 degrees C +/- 0.5 degrees C, and these were used to calculate the M:F ratio. Analysis of covariance was used to identify statistical differences between wire alloy and preactivation.Nonpreactivated (0 degrees) closing loops failed to produce an optimum M:F ratio for translational tooth movement. With increasing preactivation, the M:F ratio increased over the deactivation range for both alloys. The NiTi T-loops produced an M:F ratio of greater than 10:1 over a larger deactivation range (while still delivering a force of 50-150 g) than for the equivalent TMA T-loop. The difference in M:F between the 0 degrees and 30 degrees TMA loops was statistically significant (P0.000) but not between the equivalent NiTi loops (P0.136). There was no statistical difference between the NiTi wire alloys at any preactivation angulation.Optimum M:F ratios for orthodontic translation can be achieved by using preactivated NiTi and TMA T-loops, with NiTi loops maintaining the optimum M:F ratio over a greater range of deactivation.
Databáze: OpenAIRE
Externí odkaz: