In vitro assessment of the mechanical properties of latex and non-latex orthodontic elastics

The increased incidence of latex allergies has led to the development of no n-latex orthodontic products. The purpose of this study was to compare the mechanical properties of latex and non-latex orthodontic elastics. The elas tics tested were from 2 manufacturers (GAC and Masel) and made of 2 materia ls (latex and non-latex). The properties tested included cross-sectional ar ea, breaking force, peak load, peak stress, stiffness, modulus, hysteresis, and 24-hour load relaxation. The data were analyzed with 1-sample t tests, an analysis of variance, and the Fisher PLSD test. Between GAC and Masel, the GAC non-latex elastics had greater breaking forces than did the Masel n on-latex elastics. The Masel latex elastics had greater breaking forces tha n did the Masel non-latex elastics. The GAC non-latex elastics showed more viscoelastic properties than both the GAC latex elastics and the Masel non- latex elastics; however, the Masel elastics were more viscoelastic than the GAC elastics. Forces generated by the elastics decreased over 24 hours to an average load approximating 75% of the manufacturers' values (GAC latex, Masel latex, and Masel non-latex elastics) and to 60% for the GAC non-latex elastics. The mechanical properties of the non-latex elastics were not com parable to those of the latex elastics. Therefore, the clinical choice of e lastics should be based on the patient's medical history and the specific m echanical properties of the type of elastic.