Caldas SGFR, Martins RP, Araújo MED, Galvão MR, Silva Júnior RSD, Martins LP. Stability of beta-titanium T-loop springs preactivated by gradual curvature.
Dental Press J Orthod 2018;
22:61-67. [PMID:
29364381 PMCID:
PMC5784818 DOI:
10.1590/2177-6709.22.6.061-067.oar]
[Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2017] [Accepted: 08/22/2017] [Indexed: 11/22/2022] Open
Abstract
OBJECTIVE
Evaluate changes in the force system of T-Loop Springs (TLS) preactivated by curvature, due to stress relaxation.
METHODS
Ninety TLSs measuring 6 x 10 mm, produced out with 0.017 x 0.025-in TMA® wire and preactived by gradual curvature, were randomly distributed into nine groups according to time point of evaluation. Group 1 was tested immediately after spring preactivation and stress relief, by trial activation. The other eight groups were tested after 24, 48 and 72 hours, 1, 2, 4, 8 and 12 weeks, respectively. Using a moment transducer coupled to a digital extensometer indicator adapted to a universal testing machine, the amount of horizontal force, moment and moment-to-force ratios were recorded at every 0.5 mm of deactivation from 5 mm of the initial activation, in an interbracket distance of 23 mm.
RESULTS
The horizontal forces decreased gradually among the groups (p< 0.001) and the moments showed a significant and slow decrease over time among the groups (p< 0.001). All groups produced similar M/F ratios (p= 0.532), with no influence of time.
CONCLUSIONS
The TLSs preactivated by curvature suffered a gradual deformation over time, which affected the force system, specifically the moments, which affected the horizontal forces produced.
Collapse