Comparison of claimed and measured forces of inter-arch orthodontic elastics – an in vitro study

Abstract

Introduction: Inter-arch elastics exert specific amount of force for the required tooth movement, therefore it is necessary for the orthodontist to be familiar with force extension characteristics of selected elastic band. Aim of this study was to compare claimed and actual force of four brands of inter-arch orthodontic elastics with respect to their initial force produced and force decay over a 24-hour period in dry and moist conditions.

Material and methods: Two hundred non-latex elastics of four brands (Dentaurum, Ortho care, Opal and Class one) and five sizes (1/8, 3/16, 1/4, 5/16 and 3/8 inch) with five elastics in each group were investigated in both dry and wet conditions statically. Force measurements were made by stretching elastics with orthodontic stress and tension gauge from to 10mm to 45mm. Samples were immersed in water for 24 hours, in starched state. Repeated Measures Analysis of Variance was used for comparisons among the groups. Dry and wet measurements were tested with paired sample T tests.

Results: Statistically no significant differences were found among the groups (P = 0.09). Class one elastics showed consistently higher values than the claimed values, conversely Dentaurum elastics showed consistently lower values. The pre and post immersion data comparison revealed significant differences at 15mm stretch (P =0.009).

Conclusions: Though statistically significant differences were found between claimed and actual force, but they seem to have no clinical impact. Force extension comparisons between dry and wet samples showed some degree of force degradation but the difference was not statistically significant.