Hydroxyapatite biomaterial implanted in human periodontal defects: an histological and ultrastructural study

The purpose of the present work was to study the response of human periodontium to hydroxyapatite biomaterial particles (180-200 µm). The biomaterial was implanted in two infraosseous periodontal defects (two patients) after clearing of the granulation tissue. At two months post-surgery, biopsies were studied using light and electron microscopy. No sign of inflammation was observed, the biomaterial aggregates were surrounded either by typical fibroblasts or larger phagocytotic cells with phagocytosis vesicles containing biomaterial crystals. These intracellular crystals were noticeably smaller than the nonphagocytized ones. Some of the phagocytized crystals showed morphological signs of intracellular dissolution. The spaces between the crystals constitutive of the aggregates were filled with organic substance containing collagen fibers.Le présent travail a pour but d’étudier la réponse du parodonte humain à des particules d’hydroxyapatite de 180 à 200 µm. Le biomatériau a été implanté dans deux poches parodontales infraosseuses (deux patients) après élimination du tissu de granulation. Deux mois après l’intervention, des biopsies ont été étudiées en microscopie photonique et en microscopie électronique. Aucun signe d’inflammation n’a été décelé, les agrégats de biomatériau sont bordés soit de fibroblastes, soit de cellules phagocytaires, de taille plus importante, avec des vésicules de phagocytose renfermant des cristaux de biomatériau. Ces cristaux intracellulaires sont notablement plus petits que les cristaux non phagocytés. La morphologie de certains cristaux phagocytés traduit l’existence d’une dissolution intracellulaire. Les espaces entre les cristaux constitutifs des agrégats sont comblés par une substance organique contenant des fibres de collagène

Controlling calcium and phosphate ion release of 3D printed bioactive ceramic scaffolds: An in vitro study

his paper characterizes in an in vitro setting the release of calcium (Ca) and phosphate (PO4) of 3D printed bioactive ceramic scaffold prepared from extrudable paste containing hydroxyapatite and β-tricalcium phosphate (β-TCP). Hydroxyapatite and β-TCP were calcined at 800 °C for 11 h, fabricated into four experimental groups (100% HA, 100% β-TCP, 15%/85% HA/β-TCP, and 15%/85% HA/β-TCP (design)), sintered to 1100 °C for 4 h. Calcium and phosphorus concentrations were evaluated using ICP spectroscopy, and the release of Ca and PO4 ions during dissolution of the CaP-based scaffolds was measured by submerging in 0.05 mol/L Tris(hydroxymethyl)aminomethane-HCl and maintaining a temperature of 37 °C. The Ca and PO4 concentrations of the solutions were measured with the utilization of a calcium assay kit and a phosphate assay kit and read in a UV–visible spectrophotometer. The 100% HA scaffold group showed the greatest concentration of Ca ions (~1.9 mg/dL), but ultimately released at a lower amount as time increased; the 100% HA scaffold also showed the lowest total amount of calcium ions released over the course of evaluation. The results for the 100% β-TCP were on the opposite of the HA with the highest amount of calcium ion release over the study. While the PO4 ion release showed a similar trend as those observed with Ca ions with an apparent difference in the 100% HA scaffold group. There was nearly 0 mg/dL of the phosphate ions released in the first 24 h, in comparison to the amount of Ca ions released during the same time frame. Since various formulations can lead to different properties of these bioactive ceramic scaffolds, it is important to understand how the tailoring of this important biphasic material can impact the long-term outcome of an ever-important in vivo clinical trial in the future.Peer reviewedChemical Engineerin

Diffusion inélastique de pions positifs sur l'hydrogène aux énergies intermédiaires

Doctorat en Sciencesinfo:eu-repo/semantics/nonPublishe

Étude de l'évolution de l'orthophosphate tricalcique non cristallin en phosphate apatitique à la faveur d'une réaction chimique, à température ordinaire

The noncrystalline tricalcium phosphate Ca9(PO4) 6, nH2O begins to be hydrolyzed as soon as precipitated, and leads to the formation in the solid of HPO24 - and OH- ions : the amount of these ions increases v.s. time, till a limit compound Ca9□(HPO4) (PO 4)5(OH)□. This hydrolyze is shown by an endothermic effect of ΔH = + 12.9 ± 2.0 kJ/kg of 900 C calcined phosphate. At half reaction, the solid initially noncrystalline, crystallizes in apatite : this crystallization is shown by an exothermic effect of ΔH = — 6.1 ± 1.0 kJ/kg of 900 C calcined phosphate. This exothermic effect appearing at half reaction, allows to calculate the activation energy of this hydrolyze E = 105.3 ± 5.8 kJ/mole.Le phosphate tricalcique non cristallin Ca9(PO4) 6, nH2O subit dès sa précipitation une hydrolyse conduisant à la formation dans le solide d'ions HPO2-4 et OH - : en isotherme la teneur en ces ions croît en fonction du temps jusqu'à un composé limite Ca9□(HPO4) (PO4) 5(OH) □. Cette hydrolyse est révélée par un phénomène endothermique correspondant à ΔH = + 12,9 ± 2,0 kJ/kg de précipité calciné à 900 C. Au voisinage de la demi-réaction, le solide non cristallin cristallise en apatite : ce phénomène est révélé par un pic exothermique correspondant à ΔH = — 6,1 ± 1,0 kJ/kg de précipité calciné à 900 C. L'existence de ce phénomène exothermique à mi-hydrolyse permet de déterminer l'énergie d'activation de l'hydrolyse E = 105,3 ± 5,8 kJ/mole

A projector for large-size bubble chamber pictures

A low cost projector specially designed to project the pictures produced by the CERN 2 m bubble chamber is described. The projector projects simultaneously up to 4 pictures superposable 2 by 2, of maximum dimensions 240 mm × 50 mm at a linear magnification factor 15. A general description of the machine and a detailed description of the original elements are given. The more attractive characteristics concern the high safety level for the films and the very ease of handling. Moreover the projector is equipped with all the facilities required from a bubble chamber film projector for a rapid and efficient work. © 1976.SCOPUS: ar.jinfo:eu-repo/semantics/publishe