Search

International audience

International audience; Tribocorrosion of Ni - 30Cr model alloy was investigated for different contact pressures in LiOH H3BO3 solution at room temperature. The sliding tests were performed with a pin-on-disc tribometer designed to evaluate the synergistic effect between corrosion and wear. The combined corrosion wear degradation during sliding tests was monitored and evaluated by open circuit potential measurements and electrochemical impedance spectroscopy measurements. The sliding track morphology was investigated by SEM and profilometric measurements after sliding tests. The total material loss generated by the deterioration of the protective oxide layer due to combined chemical / electrochemical and mechanical interactions in the sliding track area was assessed from quantitative and qualitative point of view.

International audience

International audience; Purpose: To evaluate quantitatively the effect of six contemporary self-etching systems on dentin permeability by means of the electrochemical impedance technique and to correlate these results with their acidity. Methods: 36 1.1 mm thick dentin disks were embedded in a hollow polyurethane resin cylinder. The system used was a "like" permeation cell: two electrodes immersed in a 10(-1) KCl solution were attached to a potentiostat. It was connected to a microcomputer controlled frequency response analyzer, and a 10 mV sinusoidal voltage signal over a frequency range of 1 Hz to 65 kHz was applied between the electrodes. The current passing through the dentin was measured to enable a calculation of impedance expressed in a complex number. To establish an evaluation of permeability variation, the resistance was noted for all specimens before and after the application of self-etching adhesive. A pH meter used with a combined glass-electrode measured the pH of all the systems. Results: The higher decrease of the resistance of dentin samples was obtained with Experimental (EXP), which presented no significant difference with Touch and Bond (TB), Etch and Prime 3.0 (EP), and Etch Free Tenure (EF). These acidic monomers improved the dentin permeability respectively to 6.7, 5.1, 5.0 and 5.0%. The lowest values were obtained with Clearfil SE Bond (SEB) (2.0%), which showed significant difference with all the other systems. Prompt L-Pop (PLP) with 4.3% showed significant difference with EXP and SEB and no significant difference with the three other systems. The pH and permeability variation were not systematically correlated.

International audience; Tribocorrosion is a damaging process leading to a wear of metallic materials under combined actions of sliding friction and corrosion. Their interactions axe intricate, each process having an influence on the other one. The mechanical and physico-mechanical phenomena involved in tribocorrosion are studied for two stainless steels in corrosive medium. The kinetics of periodic destruction and restoration of the passive chromium oxide surface film protecting the metal from the corrosive medium was evaluated. It was found that rubbing induced hardening (or possibly induced martensitic transformation) degrades the mechanical properties, wear and corrosion resistance. The major effect of galvanic coupling between the rubbed and not rubbed axeas is illustrated by the ability to restore the chromium oxide surface film after rubbing.

International audience

Dissertação de mestrado integrado em Biomedical Engineering (área de especialização em Biomaterials, Biomechanics and Rehabilitation), Dental implants have become increasingly common for the management of tooth loss. Meanwhile, several implants still fail as a permanent solution despite the intense research on this subject. Failures on these implants are usually related to the loosening of the implant, causing inflammations, infections, decrease in bone density and release of toxic agents to the human body. On the bases of these problems are phenomena like corrosion and wear of the material composing the dental implant. In this way, it becomes necessary to better understand the mechanisms of corrosion and wear behind dental implants. The present work will increase the knowledge on the tribocorrosion mechanisms of titanium as well it will study the influence of a new surface treatment by anodization. Experimental tests will resemble the conditions presented on the oral cavity and will subject Etched and Anodized titanium samples, as well biomodified titanium samples, to tribocorrosion evaluations. The effects of the normal load and velocity of rotation on the process of tribocorrosion will be addressed and the effect of the biological material (osteoblastic cells MG63) on the degradation and corrosion behavior will be compared with the non cultivated samples. In addition, prior to cellular culture, some samples will be subjected to tribocorrosion tests to determine if the changes of the superficial properties present more affinity for osteoblast growth., Os implantes dentários tornaram-se cada vez mais comuns no tratamento da perda de dentes. No entanto, diversos implantes continuam a falhar como uma solução permanente independentemente da intensa investigação existente na área. As falhas nestes implantes são, normalmente, relacionadas com a perda de fixação do implante que conduz a inflamações, infecções, diminuição da densidade óssea e libertação de agentes tóxicos para o organismo. Na base destes problemas estão fenómenos como corrosão e desgaste do material que compõem o implante dentário. Deste modo, torna-se necessário compreender melhor os mecanismos de corrosão e desgaste por detrás dos implantes dentários. O presente trabalho vai permitir aumentar o conhecimento dos mecanismos de tribocorrosão do titânio, assim como estudar a influência de um novo tratamento de superfície realizado por anodização. Os testes experimentais vão simular as condições na cavidade oral e irão submeter amostras de titânio Etched e Anodizadas, assim como amostras Biomodificadas, a avaliação de tribocorrosão. O efeito da força normal e velocidade de rotação no processo de tribocorrosão serão abordados e o efeito da presença de material biológico (células osteoblásticas MG63) na degradação e na corrosão do material será comparado com as amostras não sujeitas a cultura. Além disso, antes da cultura celular, algumas amostras serão sujeitas a testes de tribocorrosão de modo a determinar se a alteração da superfície apresenta maior afinidade para o crescimento de osteoblastos.