Collagen fiber network infiltration : permeability and capillary infiltration

International audienceIn dentin restoration, collagen fiber network infiltration is an issue. Using data from the litterature, we have constructed a relevant numerical geometrical model of the network. The specificity of our model is that the fibers are taken into account implicitly using a regularized Heaviside function. This function is either used to set the viscosity or to localize the contact line where capillary forces are applied. A level set technique with respect to fluid infiltration front tracking in five fiber networks using the level set method and Navier-Stokes equations with capillary terms is used to point out efficient critical infiltration parameters. A variational formulation which can be implemented in FEM is proposed both for the infiltration front and the contact line. Because of lack of knowledge on fiber orientation, different configurations were tested through permeability assessment of the whole network. Fiber orientation, interfibrillar space and contact angle influence were investigated

Lecteur de thermoluminescence permettant l'analyse des spectres d'émission

Nous présentons un appareil conçu dans un but de recherche fondamentale pour obtenir des données quantitatives sur la thermoluminescence. Il peut être utilisé pour la mesure intégrale des émissions lumineuses et pour leur analyse en longueur d'onde. Nous indiquons les performances et le domaine d'emploi de l'appareil. Un exemple d'étude de spectre est donné

Measure of the hygroscopic expansion of human dentin

Background: Direct dental restoration implies a drying of the dentin substrate. This drying may induce significant strain in the dentin, affecting the bonding efficiency of the restoration. Objective: We measure the dilatation of dentine under changes of relative humidity as well as the impact of humidity on dentin elastic properties. This investigates the role of relative humidity variation during dental surgery on restoration lifetime. Methods: We have coupled an environmental chamber to control both temperature and humidity on the sample, with an optical microscope to measure precisely the strain on the sample surface, after a quantification of the measurement noise. This set-up is used on carefully prepared samples placed on a compression device to measure the elastic parameters. Results: Dentin dilates when the relative humidity increases, with a coefficient of hygroscopic expansion of typically 6.10-3 %.(%RH)-1. This dilatation occurs in about ten minutes. Young modulus and Poisson's ratio are not modified by the variation of relative humidity. Conclusions: Hygroscopic expansion is an order of magnitude larger than thermal expansion during dental surgery: around 0.3% with respect to 0.03%. These levels are low with respect to dental rupture, but may induce a significant decrease of the life-expectancy of a restoration

Influence de l'orientation outil/matiere sur l'integrite de surface des biomateriaux dentaires

La dentisterie moderne utilise la voie de la CFAO pour produire par usinage des prothèses dentaires. La rugosité est un critère important de pérennité des prothèses dentaires. L'orientation du contact outil/matière lors de l'usinage de matériaux métalliques sur la rugosité est connue et étudiée. Malheureusement, peu d'études sur la rugosité des biomatériaux non métalliques après usinage sont menées pour comprendre l'impact de l'orientation outil sur la rugosité des prothèses. L'influence, sur la rugosité, de l'orientation outil/matière lors de l'usinage, par abrasion de blocs de biomatériaux dentaires, par la voie CFAO a donc été étudiée. Trois orientations (0°, 60°, 90°) ont été testées sur des blocs de biomatériaux (Vita Enamic). L'influence de l'orientation sur la rugosité a été testée pour 4 vitesses d'avance (1000-2000-3000-4800mm/min). Les résultats montrent que l'orientation outil/matière a une influence sur la rugosité. La vitesse d'avance n'a pas d'effet sur la rugosité, quelle que soit l'orientation. Il semblerait donc que le choix d'une vitesse d'avance élevée, et une adaptation de l'orientation outil/matière en fonction de la rugosité souhaitée, permettent d'optimiser l'intégrité de surface et le temps de production

Comportement mécanique d'un Assemblage Prothétique Dentaire

Le but de cette étude est d'étudier le comportement mécanique d'un assemblage prothétique dentaire (comportant une prothèse dentaire ainsi que son support de fixation au sein de la mâchoire). Nous étudierons ainsi par le biais d'une étude numérique l'influence des paramètres de conception sur le comportement de l'assemblage considéré

Antioxidant and Cytotoxic Activities of Centella asiatica (L) Urb.

In the present study, the phenolic (Folin-Dennis) and flavonoid (colorimetric assay) constituents, antioxidant [2,2-diphenyl-2-picrylhydrazyl hydrate (DPPH) assay] and cytotoxic activities of an aqueous extract (AE) of Centella asiatica leaves were investigated. The aqueous extract (50 g/L) was obtained by infusion followed by cold maceration for 24 h. The levels of phenolic and flavonoid compounds were 2.86 g/100 g and 0.361 g/100 g, respectively. The AE showed elevated DPPH scavenging activity, with an IC50 value of 31.25 μg/mL. The AE had a promising activity against mouse melanoma (B16F1), human breast cancer (MDA MB-231) and rat glioma (C6) cell lines, with IC50 values of 698.0, 648.0 and 1000.0 μg/mL, respectively. A positive correlation was established between the level of flavonoids, antioxidant and antitumor activities

Development of mouthwash with Rosmarinus officinalis extract

Rosmarinus officinalis, which belongs to the Lamiaceaefamily, is a species of medicinal flora with therapeutic properties. In order to exploit the benefits of these properties, a mouthwash formulation was developed, with careful selection of raw materials to meet pharmacotechnical requirements. Extracts of the plant were incorporated into a mouthwash, which was shown to have inhibitory action in vitro against the micro-organisms commonly found in periodontics. Controls for assessing the quality of the drugs were carried out, quantifying phenols and flavonoids as chemical markers. Mouthwash solutions were formulated containing 0.1, 5 and 10% ethanol extract of R. officinalis; and 0.05, 5 and 10% of the hexane fraction of R. officinalis. In order to evaluate synergism, ethanol extract and hexane fraction were also added to formulations containing 0.05% sodium fluoride and 0.12% chlorhexidine digluconate. These formulations were assessed for inhibitory effect against the specific microorganisms involved in the process of bacterial plaque formation, S. mutans(ATCC25175) and C. albicans(ATCC 10231), frequently found in cases of oral infections. The agar diffusion method was used to evaluate the inhibitory activity of extracts and formulations. All mouthwash solutions displayed inhibitory activity having higher sensitivity to S. mutansfor the 5% ethanol extract+0.05% sodium fluoride, and greater sensitivity to C. albicansfor the 10% hexane fraction. Results were characterized by the appearance of a growth inhibition halo, justifying the utilization and association of extracts of R. officinalis

Diagenesis of archaeological bone and tooth

An understanding of the structural complexity of mineralised tissues is fundamental for exploration into the field of diagenesis. Here we review aspects of current and past research on bone and tooth diagenesis using the most comprehensive collection of literature on diagenesis to date. Environmental factors such as soil pH, soil hydrology and ambient temperature, which influence the preservation of skeletal tissues are assessed, while the different diagenetic pathways such as microbial degradation, loss of organics, mineral changes, and DNA degradation are surveyed. Fluctuating water levels in and around the bone is the most harmful for preservation and lead to rapid skeletal destruction. Diagenetic mechanisms are found to work in conjunction with each other, altering the biogenic composition of skeletal material. This illustrates that researchers must examine multiple diagenetic pathways to fully understand the post-mortem interactions of archaeological skeletal material and the burial environment

Appareillage destiné à l'étude de la thermoluminescence entre 77 K et 773 K

Nous décrivons un appareil permettant l'enregistrement des courbes de thermoluminescence d'échantillons minéraux ou organiques entre 77 K et 773 K avec des vitesses de chauffage pouvant aller jusqu'à 2 K/s. Ce dispositif, bien que conçu pour effectuer des mesures expérimentales de thermoluminescence, peut être utilisé pour des mesures dosimétriques de routine. Il permet l'étude de la thermoluminescence induite par différentes radiations ionisantes telles que le rayonnement gamma, les particules α, β et les ions lourds