Comparison of Different Commercially Available Orthodontic Elastomeric Chains' Force-Degradation Pattern

Methods: In an in-vitro study, ECs were divided into 6 groups, each containing 40 piece of chain, from three commercially available brands( American Orthodontics, GAC and Ortho Technology). The products of each manufactures were allocated to two groups with respect to their claimed characteristics (whether to have memory or not) and named “traditional type” and “memory type”. Each sample was stretched to twice its original length and kept constant for 1 month in 37°C distilled water. Force-extension diagrams were drawn by Universal testing machine at 0,1,8,24,72 hours and 1, 2, 4weeks. Additionally, the amount of elongation required to deliver 200gr force were calculated for chain groups. To compare the results, ANOVA and Tukey tests were performed.

Results: Force-decay rate was significantly different between traditional and memory elastomeric chains. However the curves were similar for the specimen within each group. For traditional chains, there was a substantial decay in force in the first hour and 30-40% of the force was retained at 4weeeks. The memory chains demonstrated more constant force and retained 60% of their initial force at 4 weeks. The maximum amount of elongation required to deliver 200gr forces belonged to American Orthodontics Memory chains(61.9% after 24hr) and  the minimum to Ortho Technology ECs(23.4% initially).

Conclusions: Overall, memory chains exhibited superior mechanical properties compared to traditional ones (p<0.05).  Memory chains require more elongation to deliver the same force rather than traditional ones. Memory chains of GAC and American Orthodontics showed better characteristics among all studied chains.