Influence of temperature and humidity on the long-term storage of latex and non-latex orthodontic elastics.

Abstract

The objective of this study was to evaluate the influence of long-term storage on latex and non-latex orthodontic elastics. The sample consisted of 300 orthodontic elastics, 150 latex and 150 non-latex (American Orthodontics® *(AO) and Morelli®) of medium force and a standard size of 3/16'' divided into 20 groups, 10 for each manufacturer, with 15 specimens each. The groups (G1*-G10* and G1-G10) were made up based on the manufacturer, storage temperature (ambient and refrigerated), material, and ambient humidity (exposed and non-exposed). The elastics were stretched and their forces measured in five progressive increases of 100% of their inner diameter, starting at a level of 200% stretching, by the MESDAN LAB 3000® (MESDAN, Italy) testing machine. The tests were carried out at two different times: immediately in as-received state and again after 1 year. Data were analysed using SPSS 16.0 software, the Student's t-test, one-way analysis of variance (ANOVA) and the Tukey's post-test. There was a statistically significant difference between the average forces exerted by the latex elastics compared to the non-latex elastics for all distention levels evaluated, except for 300%; however, the different storage conditions of temperature and humidity did not interfere in the mechanical properties. Both the latex and non-latex elastics may be stored under any of the conditions tested in the present study, since there were no changes in the potential of the force exerted by the elastics in relation to their percentage stretch over a 1-year period.