Experimental evaluation of latex-free orthodontic elastics' behaviour in dynamics.

Latex-free products have been introduced in orthodontics following a growth in the number of latex allergy cases reported. The aim of this study is to compare the efficiency between latex-free and latex elastics which are normally used in clinics. In this study, 80 latex-free and 80 latex elastics were divided into 4 groups of 20 elastics. Each group was exposed to a variable number of opening/closing cycles (100, 1200, 2400 or 4800), using a specially adapted machine which simulated the stretching of these elastomeric products during the dynamics of the mouth. The machine extended the elastics' inner diameter from 3 to 5 times its original dimension (the extension being comparable to that experienced during the opening/closing movements of the mouth). Following this, the elastics underwent a dynamic tensile test using the Instron 4301 machine to evaluate possible force loss and deformation. The different test results were analyzed using the Student t-test and ANOVA test of Tuckey. The test results showed differences between the two types of elastics particularly in the inner diameter behaviour: the increase in the inner diameter of the non-latex elastics' was pronounced. The forces applied by both types of elastics were similar until 2400 opening/closing cycles were reached. Thereafter, the nonlatex elastics lost a larger force (p < .01). The test results suggest that latex-free elastics must be replaced more frequently than conventional latex elastics.