[An in vitro study of the stretching time-associated force loss generated by elastomeric chains and NiTi closed coil springs].

The purpose of the study was to evaluate the force loss of orthodontic elastomeric chains with NiTi closed spring in artificial saliva by time.

METHODS: The study samples comprised 40 elastomeric chains (20 Dentaurum, and 20 G & H) and 15 NiTi closed spring (GAC). The elastomeric chains were submerged in 36,6 ºC artificial saliva and stretched on the instrument of resin plates at a distance of 30 mm. With an electronic dynamometer the delivered force was evaluated at different intervals: at baseline, after 1 day, 4, 7, 14, 21 and 28 days. Specimens of 15 NiTi coil springs were tested by dynamometer to evaluate force loss following 1, 2, or 3 months of use.

RESULTS: It was observed a significant force loss of elastomeric chains after 24 hours. There was a force loss of elastomeric chains (from 34±1.3% to 53.86±2% after 28 days of activation). NiTi springs showed force loss (~13%) following 28 days of use, with a further significant loss (~6%) at 4-8 weeks; force levels remained steady thereafter.

CONCLUSION: There was higher force loss in the different commercially elastomeric chains (~60%) in comparison to NiTi springs (21%).