engleski

Testing of working properties of orthodontic archwires by three-point bend test and changes induced by corrosion

The three-point bend test is used to assess the load-deflection characteristics of the material. The information from stress-strain curve allow insight into working properties of superelastic nickel-titanium archwires i.e. unloading forces that move teeth during orthodontic treatment. Hyaluronic acid has anti-inflammatory action and bacteriostatic effect and is therefore used as mouthwash. However, it can induce corrosion of orthodontic appliances and alter their working properties. The aim was to analyse the working properties of orthodontic archwires before and after the corrosion induced by saliva and hyaluronic acid. One group of nickel-titanium archwires (N=6) were exposed to solution that simulated human saliva (1.5 g/L KCl, 1.5 g/L NaHCO3, 0.565 g/L NaH2PO4, and 0.5 g/L KSCN) with addition of 0.9 g/L lactic acid buffer to adjust for pH of 4.8 usually measured in one- and two-day-old dental plaque. Other group (N=6) was exposed to hyaluronic acid-containing mouthwash (0.025 %). Archwires were stored in saliva for 28 days and incubated at 37°C. Mouthwash group was immersed in hyaluronic acidonce a week for 5 minutes and then restored in saliva and further incubated. The three- point bend test was performed in a group of as- received, unexposed archwires and in both exposed groups. Saliva and hyaluronic acid have similar influence on working properties or nickel-titanium orthodontic archwires, both reducing elastic properties in the unload phase compared to as-received wires (p<0.05). Hyaluronic acid had a higher effect than saliva, but the difference was not significant. Hyaluronic acid can be used as an anti-plaque and anti-gingivitis agent during orthodontic treatment without concern as working properties of fixed orthodontic appliances during levelling and alignment should not be affected.

corrosion ; mechanics ; orthodontic treatment

Financirano sredstvima Hrvatske zaklade za znanost (IP-2014-09-7500)projekt Imunosne i regenerativne implikacije korozije dentalnih materijala u djece i adolescenata (IMUNODENT).