Force Decay of 27 Orthodontic Elastomeric Chains

The aim of this investigation was to assess the efficacy and force decay of elastomeric chains based on their morphology and elongation extent.

Two-hundred-and-seventy elastics from three companies [Ortho Technology (OT), American Orthodontics (AO), G&H, 10 specimens ×27 subgroups] were elongated to 40%, 60%, and 100% and the initial forces were measured. Then after four weeks of incubation in artificial saliva, the residual forces were measured. Forces and force decays were compared across brands, morphologies, and elongation extents (α=0.001).

Forces degraded significantly over time (repeated-measures ANOVA, P<0.001). Significant differences existed among the levels of all parameters, in terms of the initial forces, residual forces, and force degradation (3-way ANOVA, P<0.001). Results of most of the Tukey post hoc tests were significant (P<0.001). The longer the elongation extent, the higher the force waste (partial correlation coefficient, r=0.885, P< 0.001).

Initial force was improved when using the OT brand and closed elastics, and by stretching the elastic to 100%. Force loss was minimized when using the G&H brand and open elastics, and by stretching to 40%. Using the OT brand and closed elastics, and 100% stretching caused the highest residual forces after a month. However, the initial forces provided by the 100% elongations were not sound. Force loss was increased by using the OT brand and closed elastics, and with 100% elongations. The lowest residual forces were seen in the AO brand, long elastics, and those elongated to 40%.