The korean journal of orthodontics (대한치과교정학회지)

The Korean Association Of Orthodontists (대한치과교정학회)
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Effect of activation and preactivation on the mechanical behavior and neutral position of stainless steel and beta-titanium T-loops

  • de Castro, Saul Matos (Department of Orthodontics, Faculty of Dental Medicine, University of Porto) ;
  • Moreira, Rui (Department of Mechanical Engineering, University of Aveiro) ;
  • Braga, Ana Cristina (Department of Production and Systems Engineering, School of Engineering, University of Minho) ;
  • Ferreira, Afonso Pinhao (Department of Orthodontics, Faculty of Dental Medicine, University of Porto) ;
  • Pollmann, Maria Cristina (Department of Orthodontics, Faculty of Dental Medicine, University of Porto)
  • Received : 2014.06.23
  • Accepted : 2015.02.09
  • Published : 2015.07.25
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Abstract

Objective: To quantify, for each activation, the effect of preactivations of differing distribution and intensity on the neutral position of T-loops (7-mm height), specifically the horizontal force, moment to force (M/F) ratio, and load to deflection ratio. Methods: A total 100 loops measuring $0.017{\times}0.025$ inches in cross-section were divided into two groups (n = 50 each) according to composition, either stainless steel or beta-titanium. The two groups were further divided into five subgroups, 10 loops each, corresponding to the five preactivations tested: preactivations with occlusal distribution ($0^{\circ}$, $20^{\circ}$, and $40^{\circ}$), gingival distribution ($20^{\circ}$), and occlusal-gingival distribution ($40^{\circ}$). The loops were subjected to a total activation of 6-mm with 0.5-mm iterations. Statistical analysis was performed using comprised ANOVA and Bonferoni multiple comparison tests, with a significance level of 5%. Results: The location and intensity of preactivation influenced the force intensity. For the M/F ratio, the highest value achieved without preactivation was lower than the height of the loop. Without preactivation, the M/F ratio increased with activation, while the opposite effect was observed with preactivation. The increase in the M/F ratio was greater when the preactivation distribution was partially or fully gingival. Conclusions: Depending on the preactivation distribution, displacement of uprights is higher or lower than the activation, which is a factor to consider in clinical practice.

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