In vitro evaluation of cytotoxicity of fixed functional appliances

The objective of this study was to evaluate the cytotoxicity of fixed functional appliances that are commonly used in the treatment of Class II malocclusion caused by mandibular retrognathia, using the MTT cell viability assays [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] (Sigma Chemical Co., Milan, Italy).

The cytotoxicity of five different fixed functional appliances commonly used in orthodontic treatments was assessed. The appliances evaluated included Jasper Jumper (American Orthodontics, Wisconsin, USA), Power Scope (American Orthodontics, Wisconsin, USA), Herbst (American Orthodontics, Wisconsin, USA), Forsus™ Fatigue Resistant Device Kits (3 M, MN, USA), and Twin Force Bite Corrector (Henry Schein Orthodontics, California, USA). Assays were conducted using one appliance from each type, resulting in a total of seven groups. Cytotoxicity testing was performed using the MTT assay on a human gingival fibroblast (HGF) cell line. Data analysis was conducted using the Kruskal-Wallis test with a significance level of p = 0.05.

All appliances demonstrated cell viability rates exceeding 90%, categorizing them as non-cytotoxic under ISO 10993-5 standards. Herbst exhibited the highest proliferation index (2.62 ± 1.13), while Power Scope (2.05 ± 1.06) and Jasper Jumper (1.90 ± 1.23) showed the lowest indices. Despite these variations, statistical analysis revealed no significant cytotoxic effects when compared to the control group (p > 0.05). All appliances were confirmed as biologically safe for cell health.

The findings demonstrate that all evaluated appliances exhibit a biocompatible interaction with HGF cells, with no evidence of adverse cytotoxic effects. These results support the safe clinical use of these fixed functional appliances in orthodontic treatment.