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Fretting in orthodontics and its test methods

Czepułkowska W., Jastrzębski W.

Archives of Materials Science and Engineering

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2018

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Vol. 94, nr 2

55--64

EN

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

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Analiza procesu tłoczenia wspornika ze stali martenzytycznej

Gronostajski Z., Krawczyk J., Polak S., Chorzępa W.

Hutnik, Wiadomości Hutnicze

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2016

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Vol. 83, nr 1

27--33

PL

Pomimo wdrażania do produkcji samochodów takich materiałów jak: stopy aluminium, stopy magnezu, kompozyty i tworzywa sztuczne, stal jest nadal materiałem dominującym w przemyśle motoryzacyjnym. Celem pracy było wykonanie analizy procesu tłoczenia wspornika ze stali martenzytycznej MAH900 a w końcowym efekcie opracowanie technologii jego kształtowania. Proces kształtowania został zasymulowany za pomocą programu MSC.Marc 2013. Kształty narzędzi przyjęto w oparciu o dokumentację z firmy Kirchhoff Polska. Dane materiałowe blachy martenzytycznej MAH900 wyznaczono w próbach rozciągania próbek wiosełkowych. Obliczenia zostały wykonane przy użyciu elementów powłokowych (typu shell) oraz bryłowo-powłokowych (shell-solid). Największe różnice między tymi dwoma modelami obserwowane są w miejscach, w których występuje pogrubienie materiału – w rzeczywistości dochodzi tam do zgniatania materiału. Elementy powłokowe w tym przypadku są niewystarczająco dokładne do wyznaczenia pól odkształceń i naprężeń ze względu na brak możliwości ich odwzorowania po grubości blachy. Na podstawie obliczeń została przygotowana technologia tłoczenia wspornika w firmie Kirchhoff. Następnie wykonano proces tłoczenia i porównano kształty wytłoczki rzeczywistej z wynikami symulacji numerycznej. W zaprojektowanym procesie wytwarzania wspornika kolumny kierownicy z blachy martenzytycznej uzyskano niewielkie różnice w kształcie wspornika otrzymanego w symulacji numerycznych z użyciem elementów bryłowo-powłokowych i wytworzonego w procesie rzeczywistym.

EN

Despite wider and wider use of novel materials such as aluminium alloys, magnesium alloys, composites and plastics in car production, steel is still the dominant material in automotive industry. The main goal of the work was to perform the analysis of stamping process a bracket made of martensitic steel MAH900 aiming to develop forming technology. The results of the stamping process simulation were compared to the experimental results. The forming process was simulated with MSC.Marc 2013. Geometry of the tools was generated based on the documentation from Kirchhoff Polska company. The material data of martensitic steel MAH900 have been determined experimentally. The calculations were made using two models, one employing shell elements and the other using shell-solid elements. The greatest differences between the two models was observed in places, where the material is thickened – actually, here, the compression of the material takes place.. The shell elements in this case are not able to represent through-thickness stresses.. The calculations were used to develop the stamping technology for the bracket implemented in Kirchhoff company. The real drawpiece shapes were compared to the numerical simulation results. Slight differences between the results of the numerical simulation using solid-shell elements and the real process’ measurements have been observed, only.

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

Łępicka M., Grądzka-Dahlke M.

Advances in Materials Science

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2016

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Vol. 16, nr 3(49)

5--14

EN

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.