Fretting occurs during orthodontic treatment or wearing prosthesis. Although weight of particles is marginal, the total releasing area is more of a concern due to amount and volume of molecules. The aim of the study was to examine the fretting wear resistance of orthodontic and prosthetic alloy Ni-Cr-Mo samples coated with Ti(C, N) and to compare them with samples without any coating. Five groups of cylindrical shape samples (S1-S5) made of Ni-Cr-Mo were coated with Ti(C, N) layers with different content of C and N. The control group (S0) was without layer. The alloys underwent fretting wear resistance tests with amplitude 100 µm, at frequency 0.8 Hz with averaged unit load: 5, 10, and 15 N for 15 min. The samples were subjected to microscopic observations using scanning electron microscope and a laser scanning microscope. Samples with Ti(C, N) coatings revealed higher fretting wear resistance. The wear in each case with Ti(C, N) coatings was over twice as low. The lowest wear and thus the highest resistance was demonstrated by sample S3 (1.02 µm) whereas in control group-S0 (2.64 µm). The use of Ti(C, N)-type coatings reduces the adverse effects of fretting wear, decreasing the amount of ions released during orthodontic treatment or wearing prosthesis.Processes 2019, 7, 874 2 of 15 surfaces' small shifts of in respect of each other as a result of the applied external loads, which are cyclic in character, can be a contact load exerted by the axial force and the tangential force. Fretting wear has also been observed to occur as a result of free vibration of the construction. Respectively to different states, Neyman [8] differs: fretting wear as a loss of mass and volume in the surface layer, fretting corrosion where oxidation of the surface layer dominates and fretting fatigue that may occur during variable load. Respectively to the mentioned different states of loads and operation, we distinguish between "fretting fatigue" and "fretting wear" [10]. The presence of areas of adhesion and micro-slips is strictly connected with the occurrence of two different wear mechanisms in them. The adhesion areas undergo cracking in the mode of contact fatigue, whereas the micro-slip areas are subjected to adhesion wear. In both cases, we observe the formation of wear products, which remain in abrasive contact. If they exhibit high hardness, they work as an abradant, accelerating the process of wear, especially in its last, catastrophic phase. Fretting almost always occurs with chemical changes of the surface except in exceptional cases of high vacuum, inert atmospheres, or precious metal contact. In active environment, where fretting corrosion takes place, wear appears sooner and is much more intensive [6,[11][12][13][14][15]. Fretting corrosion is formed in couples working in a corrosive environment. The tensions cause an increase of the surface energy and chemical reactivity. Also, in the case of fretting corrosion, products of wear are created, which are usually metal oxides [16]. Those can be the oxides removed from the su...
Study of political parties’ communication based on photographs published onlineThis article contains a description of an empirical study the aim of which was to analyze the photographs published online by two Polish political parties: Razem and Wolność KORWiN. A corpus containing 253 images and photos published by the two parties in the forth quarter of 2016 was constructed and a quantitative analysis was performed afterwards. Documentary and portrait photos, which appeared most frequently in the corpora were carefully analyzed on the basis of such factors as: the frequency at which particular persons appeared in the photos, the clothes they were wearing, the type of events depicted in the pictures and the kinds of objects which were shown most often.
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 the shape of the samples and the amplitude of the movements, calculated according to the Hertz contact problem. Fretting-corrosion tests on the 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 get through to the organism from the elements of a fixed orthodontic appliance and they may cause hypersensitivity of surrounding tissues. The amount of wear material and its total area should be tested. Originality/value: Presented are the methods of fretting wear testing in a fixed orthodontic appliance, taking into account the cognitive gap in the knowledge of the amount of abraded material from ready-made components and the value of their total area.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.