Effects of stress relaxation in beta-titanium orthodontic loops.

Abstract

INTRODUCTION:

This study evaluates the changes in the force system of the beta-titanium T-loop spring (TLS) caused by stress relaxation.

METHODS:

Ninety TLSs with dimensions of 6 × 10 mm, made of 0.017 × 0.025-in beta-titanium alloy and preactivated by concentrated bends, were randomly distributed into 9 groups according to the time point of evaluation. Group 1 was tested immediately after spring preactivation and stress relief by trial activation. The other 8 groups were tested after 24, 48, and 72 hours, and 1, 2, 4, 8, and 12 weeks. By using a moment transducer coupled to a digital extensometer indicator adapted to a universal testing machine, the amounts of horizontal forces and moments and the 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 and moments were higher (P <0.001) for group 1 compared with the other 8 groups, which were not different among themselves. All groups produced similar moment-to-force ratios (P = 0.600), with no influence of time.

CONCLUSIONS:

The TLSs preactivated by concentrated bends had progressive load decreases over time, and this effect is critical in the first 24 hours.

• Authors: Sergei Godeiro Fernandes Rabelo Caldas, Renato Parsekian Martins, Rodrigo F Viecilli, Marília Regalado Galvão, Lídia Parsekian Martins
• Journal: American journal of orthodontics and dentofacial orthopedics : official publication of the American Association of Orthodontists, its constituent societies, and the American Board of Orthodontics (Am J Orthod Dentofacial Orthop) Vol. 140 Issue 2 Pg. e85-92 (Aug 2011) ISSN: 1097-6752 [Electronic] United States
• PMID: 21803238 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2011 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.

Chemical References

• Dental Alloys
• beta titanium
• Titanium

Topics

• Analysis of Variance
• Dental Alloys
• Dental Stress Analysis
• Materials Testing
• Orthodontic Wires
• Random Allocation
• Statistics, Nonparametric
• Stress, Mechanical
• Time Factors
• Titanium