Effect of activation and preactivation on the mechanical behavior and neutral position of stainless steel and beta-titanium T-loops.
10.4041/kjod.2015.45.4.198
- Author:
Saul Matos DE CASTRO
1
;
Rui MOREIRA
;
Ana Cristina BRAGA
;
Afonso Pinhao FERREIRA
;
Maria Cristina POLLMANN
Author Information
1. Department of Orthodontics, Faculty of Dental Medicine, University of Porto, Porto, Portugal. scastro@fmd.up.pt
- Publication Type:Original Article
- Keywords:
Neutral position;
Preactivation;
T-loop
- MeSH:
Analysis of Variance;
Stainless Steel*
- From:The Korean Journal of Orthodontics
2015;45(4):198-208
- CountryRepublic of Korea
- Language:English
-
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 x 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 (0degrees, 20degrees, and 40degrees), gingival distribution (20degrees), and occlusal-gingival distribution (40degrees). 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.
