In vivo and in vitro evaluation of the mechanical properties of orthodontic elastomeric ligatures

Abstract

BackgroundElastomeric ligatures are polyurethane materials for securing arch wires into bracket slots. The mechanical properties of these ligatures deteriorate over time when exposed to different media prolonging treatment time. ObjectivesTo determine the mechanical properties of different brands of elastomeric ligatures in three media. MethodologyExperimental study assessing four brands of elastomeric ligatures: Dalton, American Orthodontics, Ormco, and Orthoclassics. A total of 120 ligatures per brand were divided equally and exposed to the oral environment, dry medium, and artificial saliva for 6 weeks. A digital force gauge was used to measure maximum tensile force and maximum tensile extension before and after exposure of elastomeric ligatures to the media. Normal distribution was assessed using Kolmogrov-Smirnoff test. Analysis of variance was used to compare mean maximum tensile force and mean maximum tensile extension between and within groups of elastomeric ligatures; level of significance was set at P < 0.05. ResultsTensile properties of all brands of elastomeric ligatures were significantly different from one another in as-received condition. After 6 weeks in the different media, all the ligatures experienced a significant reduction in maximum tensile force P < 0.0001, whereas Ormco and American Orthodontics were the only brands with significant difference in maximum tensile extension in all the media P < 0.0001. ConclusionThere were significant differences in mechanical properties of the elastomeric ligatures of the brands in as-received condition and after exposure to different media.