The prestretching effect on the force decay of orthodontic elastic chain

This in vitro study evaluated the Influence of prestretching, in the force decay of orthodontic elastic chains, at three time intervals: 2, 7 and 30 days with the brands Morelli, Orthometric and American Orthodontics. In the experimental group, prestretching was performed, stretching the elastics to increase them by 50% of their original length three times in a quick and sequential mode. All of the elastic chains were kept stretched and stored in artificial saliva at 37°C until the time of force measurement. For comparisons between the control and experimental groups, the Mann-Whitney test was used. For comparisons between time points and brands, the Kruskal-Wallis test was used, and for multiple comparisons, Miller's post-hoc test was used. The results showed statistically significant differences among the different commercial brands tested at the initial time point. The mean force at the initial time point ranged from 2.57 to 3.17 N. By day 2, the force values were between 0.97 and 1.49 N; by day 7, the values were 0.56 and 0.94 N. By day 30, the force values ranged between 0.27 and 0.66 N. We concluded that performing and duration of prestretching and the brand all Influenced the force decay of orthodontic elastic chains. Time had a greater Influence on the decay of the elastics than brand or prestretching.