Tensile Strength of Elastomeric Ligature Ties Stretched Over Large and Small Orthodontic Brackets
Date of Award
Master of Science (MS)
Objective: The purpose of this research was to investigate whether or not the larger required stretch of elastomeric ligature ties to secure an orthodontic wire into a larger sized bracket would lead to a more significant loss in tensile strength than if a smaller bracket size was used that required less of a stretch for placement of the elastomeric ligature. Methods: Maximum tensile strengths of elastomeric ligature ties from American Orthodontics and Dentsply Sirona were measured and compared after incubation for 4 weeks at 37±1oC under the following conditions: Unstretched dry, unstretched in artificial saliva, stretched and tied over a small orthodontic bracket (Forestadent Microsprint .018-inch slot lower right incisor bracket) dry, stretched and tied over a small orthodontic bracket in artificial saliva, stretched and tied over a large orthodontic bracket (American Orthodontics Master Series .022-inch slot upper right central incisor) dry, and stretched and tied over a large orthodontic bracket in artificial saliva. A three-way 2x3x2 ANOVA (Brand, Stretch Magnitude, and Artificial Saliva) analysis was performed at ⍺ = 0.05 on a sample of 240 elastomeric ligatures to determine the effect of different brands, magnitude of stretch, and presence of artificial saliva on maximum tensile strength after 4 weeks of incubation at 37ºC. Tukey’s Honestly Significant Difference test was conducted to determine statistical difference between the maximum tensile strength of unstretched, small magnitude of stretch, and large magnitude of stretch elastomeric ligatures. Results: No statistically significant difference in maximum tensile strength between American Orthodontics and Dentsply Sirona elastomeric ligature ties (p = 0.1081) was found. Presence of artificial saliva resulted in a significant reduction in maximum tensile strength (p <0.0001) between samples tested at the same stretch magnitude. Stretched elastomeric ligature ties resulted in a significantly lower maximum tensile strength than unstretched elastomeric ligatures. The maximum tensile strength in elastomeric ligatures stretched over a small magnitude was not statistically significantly different from that of ligatures stretched over a larger magnitude. Conclusions: Elastomeric ligature ties stretched over bracket wings show a significant loss of tensile strength after 4 weeks when compared to unstretched ligature ties. There was no significant statistical difference between elastomeric ligatures stretched over small and large size brackets.