Cytotoxicity and estrogenicity of Invisalign appliances

Introduction: Our purpose was to study the in-vitro cytotoxic and estrogenic properties of Invisalign appliances (Align Technology, Santa Clara, Calif). Methods: Three sets, each consisting of a maxillary and a mandibular appliance, of as-received aligners were immersed in normal saline solution for 2 months. Samples of eluents were diluted to 3 concentrations (5%, 10%, and 20% vol/vol) and tested for cytotoxicity on human gingival fibroblasts and estrogenicity by measuring their effect on the proliferation of the estrogen-responsive MCF-7 breast cancer cells. All assays were repeated 4 times for each maxillary and mandibular set, and the results were analyzed with 2-way analysis of variance (ANOVA) with appliance and concentration serving as predictors at the .05 level of significance; differences among groups were investigated with the Tukey test. Results: There was no evidence of cytotoxicity on human gingival fibroblasts and no stimulation of proliferation of the MCF-7 cell line at any concentration, indicating no estrogenicity of aligner eluents. Conclusions: The use of Invisalign appliances did not seem to induce estrogenic effects under the conditions of this experiment. (Am J Orthod Dentofacial Orthop 2009; 136: 100-3)