Comparative Toxicological In Vitro and In Ovo Screening of Different Orthodontic Implants Currently Used in Dentistry

Selecting the most biocompatible orthodontic implant available on the market may be a major challenge, given the wide array of orthodontic devices currently available on the market. The latest scientific data have suggested that in vitro evaluations using oral cell lines provide reliable data regarding the toxicity of residual particles released by different types of orthodontic devices. In this regard, the in vitro biocompatibility of three different commercially available implants (stainless steel and titanium-based implants) was assessed. Methods: As an in vitro model, human gingival fibroblasts (HGFs) were employed to evaluate the cellular morphology, cell viability, and cytotoxicity by means of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays at 24 h and 72 h post-exposure to test implants. Results: The results correlate the composition and topography of the implant surface with biological experimental evaluations related to directly affected cells (gingival fibroblasts) and toxicological results on blood vessels (hen's egg test-chorioallantoic membrane (HET-CAM) assay). The stainless steel implant exhibits a relative cytotoxicity against HGF cells, while the other two samples induced no significant alterations of HGF cells. Conclusion: Among the three test orthodontic implants, the stainless steel implant induced slight cytotoxic effects, thus increased vigilance is required in their clinical use, especially in patients with high sensitivity to nickel.