Evaluation of Tensile and Friction Resistance of Various Orthodontic Elastomeric Ligatures

Aim: This work evaluated the friction resistance and tensile strength of different colors of various commercial brands of orthodontic elastomeric ligatures with different types of wires.

Study Design: Laboratory experimental investigation.

Place and Duration of Study: Department of Dentistry, Dental School, University of North Paraná between January and December, 2015.

Methodology: Seven colors of elastomeric orthodontic ligatures (yellow, blue, light pink, dark pink, purple, green and red) from different commercial brands (GAC and Morelli) were compared for tensile strength. Three wires (NiTi, TMA and Steel 0.019X0.025-in) from GAC were also compared when friction was evaluated. For the tensile test, the ligatures were tested on a universal testing machine at 1 mm/min. For the friction test, 10 observations were made for each combination archwire-bracket. The friction test used a special apparatus fixed on a universal testing machine, and the specimens were tested at 5 mm/min with 10 mm of displacement. The results were recorded, and the means (N) were submitted to analysis of variance and Tukey’s tests at 5% significance.

Results: For tensile strength, GAC showed higher resistance with statistical difference for all colors compared to Morelli, except by the dark pink color, which showed no differences. It was verified that steel orthodontic wire (0.67N±0.36) showed lower friction compared to TMA (1.84N±0.81) and NiTi (1.53N±0.96). Regarding the brands, GAC (1.13N±0.76) showed lower friction compared to Morelli (1.56N±0.97). The pigments of the ligature interfered with the friction properties, verifying that purple (1.36N±0.72), light pink (1.05N±0.65) and dark pink (0.84N±0.53) showed less friction when compared to the other colors.

Conclusion: The pigmentation of the ligatures influences friction with the wires and the properties of resistance.