Corrosion of metal orthodontic brackets and archwires caused by fluoride-containing products: Cytotoxicity, metal ion release and surface roughness

Purpose

The aims of this study were to determine the cytotoxicity, metal ion release and surface roughness of metal orthodontic appliances after immersion in different fluoride product solutions.

Materials and methods

Twelve sets of 20 brackets and four tubes were ligated with three types of archwires: stainless steel, nickel-titanium, and beta-titanium. The samples in each archwire group were divided into three subgroups and immersed in solutions of fluoride toothpaste, 1.23% acidulated phosphate fluoride (APF), or artificial saliva without fluoride as a control group. The immersion times were estimated from the recommended time of using each fluoride product for 3 months. The samples were immersed in cell culture medium for 7 days. Primary gingival fibroblast cell viability was determined by an MTT assay. Metal ion (nickel, chromium, iron, and molybdenum) release and surface roughness were measured by inductively coupled plasma mass spectroscopy and a noncontact optical 3-dimensional surface characterization and roughness measuring device, respectively. The bracket and wire surface morphology was observed using scanning electron microscopy. The data were analysed by Two-way ANOVA.

Results

In the APF groups, the four metal ion levels and surface roughness of the brackets and archwires significantly increased, while cell viability significantly decreased, especially in the TMA subgroup. The SEM results showed that the brackets and wires in the APF groups demonstrated more lines and grooves compared with the other groups.

Conclusion

Using APF gel during orthodontic treatment with fixed metal appliances should be avoided.