engleski

Corrosion of orthodontic biomaterials - effect of pH, fluoride and hydrofluoric acid concentration from remineralization agents on elastic properties of orthodontic nickel-titanium archwires

Aim: To explore the effect of enamel remineralization agents with various concentration of fluorides on the corrosion of orthodontic nickel-titanium arch wires (NiTi). Materials and methods: Three types of NiTi with dimension of 0.508×0.508 mm were tested: uncoated (NiTi), rhodium-coated (RhNiTi) and with nitrified surface (NNiTi). Ten samples from each type of wire were immersed for 1 hour at 37° into fluoride agents - Mirafluor-k-gel, Elmex, MI Paste Plus and distilled deionized water with no fluorides (dH2O). Acidity in tested solutions and hydrofluoric acid concentrations was assessed. Three-point bend test was used to assess flexibility and resilience in load and unload. Results: Exposure of NNiTi to fluorides and dH2O induces significant decrease of flexibility in load in comparison to as-received condition (p<0.001), but not in unload. Resilience decreases in MiPaste and Mirafluor in load (p=0.004), but not in unload. In RhNiTi MiPaste, Mirafluor and dH2O increase flexibility in load in comparison to as-received condition (p=0.006), and Mirafluor and dH2O in unload (p=0.001). Flexibility of NNiTi does not change due to exposure to fluorides nor dH2O. No correlation between elastic properties and pH or hydrofluoric acid was present. Weak positive linear correlation between fluoride concentration and flexibility and resilience was found only in uncoated NiTi in load (r=0.341 and 0.312 ; p≤0.05). Conclusion: Commercial fluoride agents with various fluoride concentration do not significantly decrease unloading elastic properties of orthodontic arch wires therefore they will not affect tooth movement, regardless of wire's surface coating. Predictive value of pH, fluoride and hydrofluoric acid concentration is poor.

corrosion ; nickel-titanium alloy ; orthodontic wires

This paper was made within the project "Immunological and regenerative implications of corrosion of dental materials in children and adolescents" (IP-2014-09-7500) of the Croatian Science Foundation.