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Reims, France

Khoshniat S.,French Institute of Health and Medical Research | Bourgine A.,French Institute of Health and Medical Research | Julien M.,French Institute of Health and Medical Research | Petit M.,UFR Odontologie | And 8 more authors.
Bone | Year: 2011

Inorganic phosphate (Pi) acts as a signaling molecule in bone-forming cells, affecting cell functions and gene expression. Particularly, Pi stimulates the expression of mineralization-associated genes such as matrix gla protein (MGP) and osteopontin (OPN) through the ERK1/2 pathway. With respect to the presence of elevated extracellular calcium and Pi levels during bone remodeling, we questioned whether calcium might play a role in the Pi-dependent effects in osteoblasts. We first showed by Western blot and real-time PCR that the concomitant presence of 10. mM Pi and 1.8. mM calcium is required to stimulate ERK1/2 phosphorylation and MGP/OPN genes expression. The mechanisms involved in the cellular effects of calcium in the presence of Pi were subsequently examined. Firstly, the use of the calcium-sensing receptor (CaSR) agonist gadolinium and the G-protein inhibitor pertussis toxin enabled us to determine that a CaSR mechanism is not involved in the Pi and calcium mediated cellular effects. By transmission electron microscopy, we next demonstrated that adding 10. mM Pi to the culture medium containing 1.8. mM calcium led to the formation calcium phosphate precipitates (CaPp). Moreover, treatment of osteoblasts with exogenous pre-synthesized CaPp stimulated ERK1/2 phosphorylation and MGP/OPN genes expression. In spite of high extracellular calcium and Pi concentrations, this stimulation was blunted in the presence of phosphocitrate, an inhibitor of crystal formation. Finally, we showed that despite that CaPp are not endocytosed, their effect on ERK1/2 phosphorylation and MGP/OPN genes expression were dependent on lipid rafts integrity. In summary, we showed that calcium is required for Pi-dependent ERK1/2 phosphorylation and regulation of mineralization-associated genes in osteoblasts and that its effect could originate from extracellular-related effects of CaPp that are dependent on the integrity of lipid rafts. © 2010 Elsevier Inc. Source

Bernard P.L.,Montpellier University | Jame O.,UFR Odontologie | Ramdani S.,Montpellier University | Seigle B.,Montpellier University | And 5 more authors.
Movement and Sports Sciences - Science et Motricite | Year: 2014

Objective-We aimed at examining the effect of bruxism on postural responses on specific balance regulation and the influence of occlusal splint on mid-term and long-term postural responses. Method-The balance stability of nine healthy subjects and seven patients presenting bruxism was assessed using a force platform with and without vision on a firm floor. We analysed stabilometric data for surface, length, antero-posterior and medio-lateral projection of the center of pressure (COP) sway. During this static postural evaluation, subjects were tested in rest occlusal position, vertical occlusal position and occlusal position with orthesis. Results-The analysis showed no significant effect of bruxism on COP values in the test with OE and CE in rest occlusal position and vertical occlusal position. For the influence of occlusal splint treatment, we observed no significant difference of responses between the vertical experimental occlusal position and the vertical occlusal position with splint. Moreover, no significant difference was observed after 15 days of occlusal splint treatment and only two differences after 30 days (0.01 < p < 0.02). © 2013 ACAPS, EDP Sciences. Source

Raybaud H.,UFR Odontologie | Raybaud H.,Nice University Hospital Center | Voha C.,UFR Odontologie | Voha C.,Nice University Hospital Center | And 3 more authors.
Revue de Stomatologie et de Chirurgie Maxillo-Faciale | Year: 2012

We had for aim to describe and illustrate the artefacts observed in biopsies of the oral mucosa, as well as the impact of sending non-representative histological material to a laboratory. This article was based on an international literature review, as well as on our experience. We analysed the problems raised, for the pathologists and the histology lab-technicians, by these artefacts as well as their impact on the pathology report patient management. We suggest simple solutions. © 2012 Elsevier Masson SAS. All rights reserved. Source

Jaisson M.,UFR Odontologie | Lestriez P.,UFR Odontologie | Taiar R.,UFR Odontologie | Debray K.,UFR Odontologie
Acta of Bioengineering and Biomechanics | Year: 2011

The proposed biodynamic model of the articular disc joint has the ability to affect directly the complete chewing mechanism process and its related muscles defining its kinematics. When subjected to stresses from the mastication muscles, the disc absorbs one part and redistributes the other to become completely distorted. To develop a realistic model of this intricate joint a CT scan and MRI images from a patient were obtained to create sections (layers) and MRI images to create an anatomical joint CAD model, and its corresponding mesh element using a finite element method. The boundary conditions are described by the external forces applied to the joint model through a decomposition of the maximum muscular force developed by the same individual. In this study, the maximum force was operating at frequencies close to the actual chewing frequency measured through a cyclic loading condition. The reaction force at the glenoid fossa was found to be around 1035 N and is directly related to the frequency of indentation. It is also shown that over the years the areas of maximum stresses are located at the lateral portion of the disc and on its posterior rim. These forces can reach 13.2 MPa after a period of 32 seconds (s) at a frequency of 0.5 Hz. An important part of this study is to highlight resilience and the areas where stresses are at their maximum. This study provides a novel approach to improve the understanding of this complex joint, as well as to assess the different pathologies associated with the disc disease that would be difficult to study otherwise. Source

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