Force decay and color stability of traditional and enhanced elastomeric chains: single center, double-blind randomized clinical trial

Abstract

Backgrounds and Objectives: Elastomeric chains are commonly used to apply force for orthodontic dental movements. However, force decay and discoloration are two important weak points of these materials. The present study intended to compare the force decay and color stability of different types of elastomeric chains. Materials and Methods: This in vitro study was conducted on six elastomeric chain groups including thermoplastic (TP) and thermoset (TS) chains manufactured by American Orthodontics, Ormco, and G&H Orthodontics. Forces of the elastomers were measured at initial, 1 h, 1 day, and 1, 2, 3, 4, 5 and 6-week intervals using a universal testing machine. Chain elongation needed to provide a 250 g force was determined. The ΔE of each group was calculated by a spectrophotometer following immersion of specimens in tea media for 6 days. Data were analysed by SPSS 22 using repeated measure ANOVA and two-way ANOVA (P<0.05). Results: During 6-week period, the percentage of initial force in TS (62.21%) chain was significantly less than TP (44.36%) elastomeric chains (P <0.05) and the lowest and highest force decay were observed in AO and GH products, respectively. In all groups, the highest percentage of force dacay occurred in the first week. The percentage of TS (49.1%) chain elongation was significantly higher than that of TP (35.3%) types (P <0.05) and the highest percentage of elongation was detected in OR products. TS chains showed significantly better color stability (ΔE=17.54±2.19) than TP chains(ΔE=20.89±2.45); and OR and GH products were superior to AO in terms of color stability. Conclusion: According to the findings, TS elastomeric chains were superior to TP in terms of force decay and color stability. Key Words: Elastomeric chains, Force decay, Orthodontics.