The aim was to assess the influence of long-term in vivo exposure, debris accumulation and archwire material on static and kinetic friction force among different types of brackets and archwires couples. Material and Methods: Friction testing was performed among four lower incisors' brackets, conventional and self-ligating (SL), coupled with either nickel-titanium or stainless steel archwires, as-received and in vivo exposed in 18 subjects. The friction testing was performed for a sliding distance of 14 mm at a speed of 10 mm/min, with a starting force of 0.2 N. Wear and quantitative assessment of debris accumulation was performed on pictures of brackets obtained using a scanning electron microscope. Non parametric tests were used for statistical analysis. Results: Only bracket type, but not exposure duration, amount of debris accumulation, archwire material or their manufacturer, was significantly correlated with both static (rho = 0.602, P ( 0.001) and kinetic (rho = 0.584, P ( 0.001) friction force. Within each bracket type no significant difference was observed between as-received and in vivo exposed brackets for any friction parameter except for the SL brackets in which significantly higher static and kinetic (P = 0.001, at least) friction forces were seen in in vivo exposed SL brackets (164.9 cN and 217.63 cN, respectively) in comparison with as-received SL brackets (19.69 cN and 55.72 cN, respectively). Conclusion: A significant correlation was seen between friction force and bracket type, while treatment duration, amount of debris accumulation, archwire material or their manufacturer was not significantly correlated to it. Nevertheless, higher friction forces were measured among in vivo aged SL brackets in comparison with as-received ones.
COBISS.SI-ID: 33096921
In biomedical applications, NiTi alloys are used mainly because of their favourable shape memory and superelastic properties. However, in many applications the tribocorrosion properties of these alloys can be of critical concern. For this reason the electrochemical and tribocorrosion properties of superelastic NiTi sheet and orthodontic archwire were studied, taking into account their microstructures and the effect of different surface finishes. In the case of the electrochemical tests, samples were tested in artificial saliva, whereas in the tribocorrosion tests the experiments were performed in ambient air, distilled water, and artificial saliva, the latter as a corrosive medium. In these tests, the total wear rate of the alloy samples was determined, together with the corresponding chemical and tribological contributions. It was confirmed that the microstructure of the investigated alloys had a significant effect on the measured electrochemical and tribocorrosion properties.
COBISS.SI-ID: 1982311
Polyethylene glycol (PEG)- and polydimethylsiloxane (PDMS)-based corrosion protection coatings of the AISI 316L stainless steel surface were investigated. X-ray photoelectron spectroscopy (XPS) was used to confirm successful deposition of the coatings on the substrate as well as to estimate the thickness for both coating types. Contact angle measurements were used to evaluate wetting properties of noncoated, PEG-coated, and PDMS-coated substrates. Hydrophobicity was achieved by applying PDMS coating on the substrate. Potentiodynamic measurements established enhanced corrosion stability of PEG- and PDMS-coated stainless steels. Electrochemical impedance spectroscopy was also performed. It showed superior corrosion protection vs immersion time dependence for PDMS coating in NaCl solution compared to PEG coating.
COBISS.SI-ID: 1143210