Journal Article

Stress relaxation and recovery behaviour of composite orthodontic archwires in bending

SW Zufall and RP Kusy

in The European Journal of Orthodontics

Published on behalf of European Orthodontics Society

Volume 22, issue 1, pages 1-12
Published in print February 2000 | ISSN: 0141-5387
Published online February 2000 | e-ISSN: 1460-2210 | DOI:
Stress relaxation and recovery behaviour of composite orthodontic archwires in bending

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The viscoelastic behaviour of prototype composite orthodontic archwires was evaluated using a bend stress relaxation test. Archwires having 10 different fractions of reinforcement were subjected to constant bending radii in a water bath at 37°C for time periods of up to 90 days. The wires were subsequently released and left unconstrained for the same testing conditions. Creep-induced changes in the unconstrained bending radii of the wires were measured at specific times during both phases (stress relaxation and recovery) of the test. The statistical analysis showed that stress relaxation behaviour was strongly correlated with the archwire reinforcement level. The final relaxation varied, with decreasing reinforcement, from 2 to 8 percent. Archwire recovery was not correlated with reinforcement level, and revealed a final viscous loss of only 1 per cent. The relaxed elastic moduli in bending of the composite wires were similar to the elastic moduli in bending of several conventional orthodontic archwire materials. Losses that were associated with the viscoelastic behaviour varied with decreasing reinforcement level from 1.2 to 1.7 GPa. Because these modulus losses were minimal, each archwire retained sufficient resilience to be applicable to the early and intermediate stages of orthodontic treatment.

Journal Article.  0 words. 

Subjects: Restorative Dentistry and Orthodontics

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