engleski

Biological effect of corrosion of nickel- titanium orthodontic archwires – cytotoxicity on cells of the gastrointestinal tract

Objective: The aim of the research was to explore the effect of the products of corrosion of nickel-titanium (NiTi) orthodontic alloys in saliva on human cells of gastrointestinal tract. Methods: Eighteen samples of NiTi archwires (0.020x0.020'') were immersed in artificial saliva with pH 4.8 at the temperature of 37°C. It was a simulation of oral cavity during orthodontic treatment with fixed appliances in a patient with poor oral hygiene and high plaque accumulation in bracket slots. The dynamics of nickel and titanium ions release were recorded 3th, 7th and 14th day by inductively coupled plasma-mass spectrometry. Biological effect of Ni and Ti ions was explored on cell lines of human tongue CAL 27, liver HEP G2 and colon Caco-2 after exposure of 24, 48 and 72 hours to real concentration of corrosion products, 5x concentration and dilutions of 0.5x and 0.1x. Experiments were performed in two replicates and repeated twice. Results: Concentration of 30.4 µg/L Ni and 17.3 µg/L Ti in saliva (together 42.3 µg/L) were the maximum values found during 14 days of exposition of NiTi to saliva which did not induce cytotoxic effect. Increase in concentration of Ni and Ti tend to increase cytotoxicity, Ti more than Ni. Significant decrease in viability of all cell lines, with large effect size, is present when concentration both metals is at least 162 µg/L. It is characterized as moderate to strong cytotoxicity and comprises of combination of 75.5 µg/L Ni and 86.5 µg/L Ti or 128 µg/L Ni and 44.9 µg/L Ti (p<0.001 ; η2=0.853-0.971). The lowest concentrations that induce cytotoxicity are 75.5 µg/L Ni and 44.9 µg/L Ti, which is 2.5x higher than concentration released during two weeks. Conclusion: Corrosion of NiTi archwires in low pH saliva do not induce major cytotoxic effect and would not have a clinically important impact.

corrosion ; nickel-titanium alloy ; orthodontic wires ; cytotoxic effects

Granted by Croatian Science Foundation HRZZ-IP- 2014-09-7500