Seyed Mohammad Mousavi - Assistant Professor, Department of Orthodontics, School of Dentistry, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
Sara Mahboubi - Assistant Professor, Department of Orthodontics, School of Dentistry, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
Salmeh Kalbassi - Orthodontist, Private Practice, Tehran, Iran
Vahid Rakhshan - Dentist, Private Practice, Tehran, Iran

Aim: The aim of this investigation was to assess the efficacy and force decay of elastomeric chains based on their morphology and elongation extent.Methods: Two-hundred-and-seventy elastics from three companies [Ortho Technology (OT), American Orthodontics (AO), G&H, ۱۰ specimens ×۲۷ subgroups] were elongated to ۴۰%, ۶۰%, and ۱۰۰% 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=۰.۰۰۱).Results: Forces degraded significantly over time (repeated-measures ANOVA, P<۰.۰۰۱). Significant differences existed among the levels of all parameters, in terms of the initial forces, residual forces, and force degradation (۳-way ANOVA, P<۰.۰۰۱). Results of most of the Tukey post hoc tests were significant (P<۰.۰۰۱). The longer the elongation extent, the higher the force waste (partial correlation coefficient, r=۰.۸۸۵, P< ۰.۰۰۱).Conclusion: Initial force was improved when using the OT brand and closed elastics, and by stretching the elastic to ۱۰۰%. Force loss was minimized when using the G&H brand and open elastics, and by stretching to ۴۰%. Using the OT brand and closed elastics, and ۱۰۰% stretching caused the highest residual forces after a month. However, the initial forces provided by the ۱۰۰% elongations were not sound. Force loss was increased by using the OT brand and closed elastics, and with ۱۰۰% elongations. The lowest residual forces were seen in the AO brand, long elastics, and those elongated to ۴۰%.

Chain Morphology, Elastomeric Chains, Force Decay, Stretching, Space Closure