Comparison of Cell Viability and Chemical Composition of Six Latest Generation Orthodontic Wires

Abstract

Orthodontic wires are made of alloys containing different metals, including nickel. It is important to evaluate their biocompatibility prior to use, owing to their long-term use in patients. This in vitro study compared the cytotoxicity and chemical composition of six latest orthodontic wires: Fantasia®, Tanzo®, FLI®, NT3®, DuoForce®, and Gummetal®. The before-use group consisted of wires that were not used in the mouth, and the after-use group consisted of wires that were used in the mouth for two months. The wires were placed in contact with human gingival fibroblasts (HGF) for 72 h, and cytotoxicity was determined using the resazurin test. The chemical composition and surface characterisation were evaluated by spectrometry and scanning electron microscopy. The groups were compared using ANOVA and Kruskal–Wallis test. Only the FLI® wires produced a 36% reduction in HGF viability ( p < 0.05 ) and presented greater irregularities and loss of polymer structure. After-use wires showed a significant reduction in the percentage of nickel and the appearance of new elements (oxygen and carbon). Therefore, it can be concluded that no toxic ion release was noticed in this study. Rhodium-coated wires were more stable than PTFE-coated wires, and only the FLI® wires showed a slight cytotoxic effect.

Functional Surface Coatings on Orthodontic Appliances: Reviews of Friction Reduction, Antibacterial Properties, and Corrosion Resistance

“…Katić Višnja et al [ 170 ] and Milena Carolina de Amorim et al [ 184 ] both suggested that rhodium coating reduces the corrosion resistance and electrochemical resistance of NiTi archwires in artificial saliva, making them more susceptible to localized pitting corrosion on the surface. Lina M. Escobar et al [ 185 ] described rhodium-plated NiTi archwire as having a significantly rougher surface and many scratches on its surface after testing. This indicates that the wear resistance of rhodium plating is also less than satisfactory.…”

“…The corrosion rate of a PTFE-coated NiTi archwire was 10 times lower than that of uncoated NiTi substrates [ 192 ]. However, PTFE may exhibit slight cytotoxicity to fibroblasts—approximately 36% [ 185 ]. Therefore, careful consideration is needed when choosing this material.…”

Toxicity of Metal Ions Released from a Fixed Orthodontic Appliance to Gastrointestinal Tract Cell Lines

“…Nowadays, fibroblast cell lines (periodontal ligament, gingival, or dermal [ 9 , 10 , 11 , 12 , 13 , 14 ]), gastrointestinal tract cell lines [ 15 , 16 ], and sometimes yeast [ 17 , 18 ] are most commonly used for testing. Research has focused mainly on NiTi or stainless (arch)wires [ 2 , 13 , 19 , 20 ], brackets [ 2 , 12 , 14 ], and bands [ 2 , 9 , 10 , 16 , 21 ].…”