Le canal dentaire et le nerf alvéolodentaire

International audienc

La microarchitecture du tissu osseux

Le capital osseux se constitue au cours de la vie par les mécanismes de modelage et de remodelage. Le tissu trabéculaire est constitué par un ensemble de travées (plaques et piliers) dont la répartition est hautement anisotrope : les travées se disposent parallèlement à la résultante des lignes de contraintes (Loi de Wolff). La microarchitecture trabéculaire apparaît conditionnée par les contraintes mécaniques qui s’exercent sur les pièces squelettiques. Cependant, peu de méthodes sont actuellement validées cliniquement pour apprécier et suivre l’évolution de la microarchitecture dans les ostéopathies. Les études les plus développées portent sur l’appréciation microarchitecturale par histomorphométrie osseuse grâce à l’utilisation de nouveaux algorithmes permettant d’apprécier en 2D différentes caractéristiques trabéculaires dont la connectivité. Plusieurs travaux ont montré que l’appréciation de la microarchitecture devait utiliser plusieurs techniques indépendantes. La microtomographie X (microCT), la micro IRM, le synchrotron permettent aussi de mesurer en 3D l’architecture trabéculaire de façon non destructive sur des prélèvements osseux. Cette revue décrit l’évolution des connaissances sur la microarchitecture osseuse, son rôle dans les maladies osseuses comme l’ostéoporose et les différentes méthodes d’évaluation histologique en 2D et en 3D

Multiple myeloma and bone

Multiple myeloma (also called Kahler\u27s disease [MM]) is a hematological malignancy of B lymphocytes characterized by the expansion of a malignant plasma cell clone in the bone marrow. Five thousand cases of myeloma are diagnosed each year in France, 54% in men. In almost all cases, the malignant plasma cells secrete a monoclonal immunoglobulin or an immunoglobulin fragment (free light chain) which can be detected in the blood and/or urine. This is currently the most common way of diagnosis after having prescribed an electrophoresis or an immunofixation of serum proteins. Indeed, MM is often preceded by a monoclonal gammopathy of undetermined significance (MGUS), which requires a long term biological monitoring. MGUS are 100 times more common than MM (and are observed in 3–4% of the population after 50 years) and their evolution towards an overt myeloma is approximately 1% per year. MM is a hematological malignancy whose incidence is correlated to the aging of the population (the mean age at diagnosis is about 70 years)

New microscopies, biomaterials: Two new axes for Morphologie

International audienc

Rachitismes et ostéomalacies à l’âge adulte

La principale cause de l’ostéomalacie chez l’adulte est la déficience sévère et prolongée en vitamine D, facilement reconnue aujourd’hui par le dosage de la 25-hydroxyvitamine D [25(OH)D]. Le contexte clinique, des anomalies biologiques phosphocalciques, des anomalies sur les examens d’imagerie (radiographies standard, scintigraphie osseuse), une densité parfois très basse mesurée en densitométrie osseuse, permettent d’évoquer la possibilité d’un trouble de la minéralisation de type ostéomalacique, diagnostic éventuellement confirmé par les données histomorphométriques de la biopsie osseuse trans-iliaque après double marquage aux cyclines. Une cause à la carence en vitamine D doit être recherchée et traitée. La supplémentation simple en vitamine D permet de guérir les patients. Des formes rares d’ostéomalacie, dénommées rachitismes vitamino-D-résistants (dépendants, type 1 et 2), sont dues à une anomalie génétique enzymatique (rachitisme pseudo-carentiel de Prader ou rachitisme vitamino-D-résistant de type 1, lié à un déficit en 1-alpha hydroxylase) ou à une anomalie du récepteur à la vitamine D (VDR ; rachitisme vitamino-D-dépendant de type 2) créant une résistance des organes cibles à l’action de la vitamine D. Dans cette dernière forme, le traitement est difficile, nécessitant le recours à des doses pharmacologiques fortes de vitamine D, en complément de la forte supplémentation calcique

Hypophosphatasie : diagnostic et conduite à tenir

International audienc

Disuse induced by botulinum toxin affects the bone marrow expression profile of bone genes leading to a rapid bone loss.

OBJECTIVES: Molecular events occurring in the bone marrow microenvironment of an immobilized mouse limb after Botulinum toxin (BTX) injection haven\u27t been characterized. BTX injection induces a localized disuse in which the tissue events have well been characterized. METHODS: BTX injection was performed in the right quadriceps; saline injection in the left side was used as control. Mice were sacrificed at 0, 7, 14, 21 and 28 days; tibias were used for microCT analysis; bone marrow from femurs for RT-PCR analysis. RESULTS: MicroCT revealed bone loss and microarchitectural damages on the immobilized side as from 7d; cortical area tended to be lower on the immobilized limb at 28d. Gene expression of formation factors was altered as from 7 days post-BTX: alkaline phosphatase, Tgfβ1, Lrp5, Sfrp2. Only Sfrp2 and Lrp5 were maintained altered until 28d. Expression of Dkk1 increased from 21d and represented a late inhibitor of formation. Gene expression of resorption markers increased as from 7d (Rankl, Tracp, Il1α, Il1β and Il6) and was maintained until 28d for Tracp and Il6. CONCLUSION: A localized disuse induces rapid modifications in the bone marrow gene expression leading to bone loss due to an early decrease of formation associated with an increase in resorption

Beta-tricalcium phosphate and bone surgery : Editorial

International audienc

Modelage et remodelage au cours de l’ostéo-intégration

Modeling is a group of cellular activities implicating osteoblasts in the development of various skeletal bones in the embryo and fetus. Remodeling is a complex adaptive process involving the coordinated action of osteoblasts and osteoclasts. It occurs once the skeleton is mature. Intercellular signaling pathways involve a great number of cytokines and growth factors. However, bone modeling, occurring by direct action of osteoblasts without prior action of osteoclasts, can occur in some circumstances, especially when in contact with biomaterials such as implants and grafted materials. We reviewed the basic concepts of cell coupling and the microscopic aspects of transition from modeling to remodeling in direct contact with dental implants and biomaterials. Bone quality is greatly improved by remodeling which is associated with the deposit of lamellar bone, the biomechanical properties of which are superior to those of non-lamellar bone formed by modeling

Effects of aluminum on cells and tissues

Aluminum (Al, also written aluminium) is the most abundant metal of the earth crust (about 8.2%) although it is never found as a free element in nature. The first chemist who isolated the metal was HD. Oersted in 1825 but the most effective process was discovered in 1886–1888 by CM. Hall, PLT. Héroult and KJ. Bayer. Large amounts of the metal were extracted from bauxite, an aluminum-rich ore discovered near Les Baux de Provence, in the southern part of France. Today the Al production is about 57,889 thousand tons a year (in 2015) [1]. Al is largely used in various industries: transport (25%, i.e. airplanes, boats…), construction (25%, i.e. windows, structures…), packaging (17%; i.e., food, containers, bins, soft packages, foils…) (Fig. 1), electrical engineering (10%, i.e. cable, bus bars…); machinery and equipment (10%) and other purposes including cosmetics and food additives