It is in the clinician’s interest to select the least hazardous devices and materials among the many offered by manufacturers. The polymer chosen is important; some polymers have been reported to be hazardous, and these are quite often used in direct contact with human tissues. For protection, the clinician could test the material’s extract in water according to an ISO standard, but the tests require sophisticated means and specific knowledge. Its simplified version, however, can be successfully used, since it requires only the observation of the aqueous solution of potassium permanganate, in which the polymer samples were immersed. Initially purple, the solution discolors as the colored ions are reduced, while the released ingredients are oxidized. The faster and more intense the discoloration, the higher the amount of leached ingredients. World J Orthod 2003;4:157–161.