Evaluation of tensile properties of several brands of elastomeric ligatures used in Iran

ABSTRACT

Elastomeric ligatures are used to secure archwires into orthodontic brackets. Unless the ligatures show adequate tensile properties, they may tear while inserting in the brackets or between patient's appointments. The latter may cause unwanted tooth movement and prolong orthodontic treatment. In this study the comparison of tensile properties [tensile strength, extension to tensile strength, and toughness] of seven commercially available molded clear elastomeric ligatures was performed. In this experimental laboratory-based study, eiastomeric ligatures were obtained from American Orthodontics, Ortho Technology, GAC, Techno Tak, All Star, Dentaurum and ITO companies and their tensile properties were measured using Zwick testing machine with 5mm/min cross head speed in the as-received condition and after 28 days immersion in a simulated oral environment. The data was analysed by SPSS software. All of the ligatures tested showed a significant decrease in tensile strength, extension to tensile strength and toughness excluding ITO's toughness after 28 days [P<0.001], Different brands of elastomeric ligatures showed significant differences in tensile properties both in the as-received condition and after 28 days immersion in the simulated oral environment [P<0.001]. Under the study conditions, ligatures from American Orthodontics and Techno Tak companies showed superior tensile properties and ligatures from Ortho Technology company exhibited weaker tensile features compared to other groups. There were significant differences in tensile properties of different brands of elastomeric ligatures in both the as-received condition and after 28 days immersion in the simulated oral environment. There was a significant reduction in strength properties of all types of elastomeric ligatures after 28 days immersion in a simulated oral environment. Thus, it is recommended that all ligatures should be replaced at each visit to reduce risk of tearing