Evaluation of the effect of different stretching patterns on force decay and tensile properties of elastomeric ligatures

Abstract

Background: There have been numerous researches on elastomeric ligatures, but clinical conditions

in different stages of treatment are not exactly similar to laboratory conditions. The aim of this

in vitro study was to simulate clinical conditions and evaluate the effect of three stretching patterns

on the amount of force, tensile strength (TS) and extension to TS of the elastomers during 8 weeks.

Materials and Methods: Forces, TS and extension to TS of two different brands of elastomers

were measured at initial, 24 h and 2, 4, and 8-week intervals using a testing machine. During the

study period, the elastomers were stored in three different types of jig (uniform stretching, 1 and

3 mm point stretching) designed by the computer-aided design and computer-aided manufacturing

technique in order to simulate the different stages of orthodontic treatment.

Results: The elastomeric ligatures under study exhibited a similar force decay pattern. The maximum

force decay occurred during the fi rst 24 h (49.9% ± 15%) and the amount of force decay was

75.7% ± 8% after 8 weeks. In general, the TS decreased during the study period, and the amount

of extension to TS increased.

Conclusion: Although the elastic behavior of all ligatures under study was similar, the amount

of residual force, TS and extension to TS increased in elastomers under point stretching pattern.

Key Words: Elastomeric ligatures, extension to tensile strength, force decay, tensile strength