Effects of autoclaving versus cold chemical (glutaraldehyde) sterilization on load-deflection characteristics of aesthetic coated archwires.

Introduction: The effect of any sterilization methods (cold [chemical] or hot) on load-deflection characteristics of aesthetic coated archwires has not yet been investigated. Thus, we assessed it.

Methods: In this experimental in vitro study, 90-coated archwires from 3 brands were purchased. Ten wires from each brand (n=30) underwent cold and 10 underwent hot sterilization, while 10 left unsterilized as negative controls. Load-deflection curves were established for each wire (as five 0.2mm intervals between 1.0 and 1.8mm displacements), using a three-bracket test. After determining the plateau phase that was present in all wires, the averages of plateau phase pertaining to loading and unloading curves and their discrepancies (hysteresis) were calculated for each subgroup (n=10). Average plateau values were compared using two-way ANOVA, Tukey, and independent-samples t-test (α=0.05).

Results: Average loading and unloading values were 906.6±129.7 and 295.9±84.5g respectively (t-test P<0.0001). Comparing loading plateaus, ANOVA indicated significant difference among wire brands (P<0.0001) but not among sterilization types (P=0.4793). Comparing unloading plateaus, ANOVA showed significant differences among wire brands (P<0.0001) and sterilization types (P=0.0008). Tukey showed that only cold sterilization and negative control differed significantly (P<0.001); cold and hot sterilization methods, or control and autoclaving were not significantly different (P>0.05). Comparing hysteresis plateaus, ANOVA indicated difference among wire brands (P<0.0053) but not among sterilization types (P=0.9166).

Conclusions: Cold sterilization might reduce unloading plateau of orthodontic wires, but sterilization in general might not affect loading or hysteresis plateaus. Different brands had different plateaus of loading, unloading and hysteresis.