Effect of disinfecting solutions on the mechanical properties of orthodontic elastomeric ligatures

To assess the effect extended exposure to disinfectant solutions has on the tensile load at failure and glass transition temperature (T(g)) of orthodontic elastomeric ligatures.

Elastomeric ligatures from three manufacturers: Rocky Mountain Orthodontics (RMO, Denver, Colo), American Orthodontics (AO, Sheboygan, Wis), and 3M Unitek (3M, Monrovia, Calif) were exposed to two disinfectant solutions, Vital Defense-D and Cidexplus, for up to 28 days. Unexposed ligatures were also tested. Tensile load at failure was determined by stretching the ligatures using a universal testing machine until they fractured. Glass transition temperature was determined using differential scanning calorimetry (DSC).

For tensile load at failure and glass transition temperature of the ligatures, significant differences were observed among the different manufacturers and exposure times. Type of disinfectant solution was a significant factor with T(g), but not with failure load. The 3M ligatures had the highest tensile load at failure and most positive T(g) followed by AO and RMO, respectively. Compared to unexposed ligatures, strength significantly decreased after one hour of disinfectant exposure. Glass transition temperature was also significantly affected with extended disinfectant exposure, but the different disinfectants changed T(g) in opposite directions.

Exposure of elastomeric ligatures to disinfectant solution for one hour or more decreases their strength.