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Tribology of Orthodontic Materials (TOM)


Orthodontic treatments are increasingly applied to correct teeth alignment and occlusion problems. In France, for instance, recent studies show that nearly 1 million young adolescents have undergone such treatment. The principle of orthodontic treatments is to impose a continuous and slow displacement of teeth by adjusting tension forces between the brackets (stuck to the teeth), and an arch-wire.

Recent studies show that friction resistance between the arch-wire and the bracket contacts plays a critical role in the treatment quality. Indeed, high friction resistance induces over-stressing, which can damage the periodontal ligaments and generates fastidious and expensive clinical complications. Moreover, friction will induce wear of the bracket and arch-wire materials activating the toxic spreading of Nickel through the body. Current research focuses on the application of specific surface treatments to reduce wear and friction resistance.

However, an exhaustive survey of the literature shows that most of the current in vitro tests are conducted under basic steady state static loading, without considering the micro perturbations induced by mastication and/or the aggressive medium associated to saliva. The objective of this project is to develop new procedures providing quick and relevant information to characterize and optimise specific hardwearing and low friction surface treatments.

The applicant (a scientist in the field of surface coating engineering), working in the LTDS (Host institution specialized in the tribology area), will first define a representative sliding loading combining macro and micro fretting slidings. This loading condition will be reproduced on an adapted environmental fretting wear test, allowing temperature control and artificial saliva conditions. An optimised friction and wear quantification test protocol will be defined and validated through comparisons with in vivo results.

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