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Surface analysis for signs of corrosion of fixed orthodontic appliances used in vivo

100%

Łępicka M. , Grądzka-Dahlke M.

2016

tom Vol. 16, nr 3(49)

5--14

The objective was to evaluate and assess the surface quality of fixed orthodontic appliances after intraoral usage for several months. Nine sets of orthodontic brackets by three different manufacturers and twelve archwires differing in chemical composition were analyzed in a scanning electron microscope with an energy dispersive X-ray analyzer for signs of corrosion. Obtained results showed that the majority of the evaluated appliances displayed no traces of corrosion. Machining or casting defects hardly ever act as the origins of corrosion processes. However, some samples displayed signs of corrosion of a galvanic and pitting nature. The authors claim, that despite the surface defects, most of the appliances were able to retain the desired corrosion resistance, although in some cases these flaws could act as the origin of corrosion processes.

Fretting in orthodontics and its test methods

100%

Czepułkowska W. , Jastrzębski W.

tom Vol. 94, nr 2

55--64

Purpose: A review of the literature regarding the occurrence of fretting wear in orthodontics and its test methods have been presented. Design/methodology/approach: The influence of micro-movements occurring in the oral cavity on the occurrence of fretting wear in a fixed orthodontic appliance is discussed. The fretting test methods were analysed, taking into account tine shape of the samples and the amplitude of the movements, calculated according to the Hertz contact problem. Fretting-corrosion tests on tines wear of materials are included. Findings: Fretting occurs between the bracket and the orthodontic archwire in a fixed appliance. The test of the amount of wear material mainly uses samples created for the needs of the device. The test of ready-made components of a fixed appliance usually relate to the value of the coefficient of friction. The use of coatings increases the coefficient with the simultaneous reduction of the amount of wear material. Fretting-corrosion occurring in the oral environment has a negative impact on the wear of materials. The value of the total area of abraded material after fretting is unknown. Research limitations/implications: Particles of fretting wear