This study aimed to evaluate and compare the leaching behavior of four clear aligner systems: Invisalign®, Eon®, SureSmile®, and Clarity®. For each system, three sets of aligners were obtained, sectioned, and immersed in glass vials containing various ethanol–water mixtures: 100% ethanol, 75% ethanol/25% water, 50% ethanol/50% water, 25% ethanol/75% water, and 100 percent water. The samples were incubated at 37 °C for two weeks. Leached compounds were analyzed using gas chromatography–mass spectrometry (GC-MS), revealing a total of eleven chemical substances. Benzene-1,3-bis(1,1-dimethylethyl) was consistently detected across all four aligner systems in the 100 percent and 75 percent ethanol solutions. No statistically significant differences were observed among the systems regarding the confirmed leaching, except for Eon®, which showed significant variation in the number of leached substances across different immersion solutions. Overall, the systems demonstrated variable leaching levels, with Invisalign® exhibiting the lowest and Eon® the highest number of leached chemicals. Importantly, none of the aligners released detectable amounts of bisphenol-A (BPA).
