Développement et applications des biocéramiques

As a relatively new biomaterial, silicon nitride (Si3N4) is currently used as an arthrodesis device in the cervical and thoracolumbar spine, and it is under consideration as a bearing material in total joint arthroplasty. In this paper, the development and validation of the manufacturing processes used in the production of Si3N4 biomedical implants are presented and discussed. Manufacturing was conducted in a facility specifically dedicated for this purpose using processes designed to yield net shape intervertebral spinal spacers by conventional dry-pressing, CNC machining of components in the green state, sintering, and hot isostatic pressing. These manufacturing methods were industrialized using Taguchi fractional factorial experimental designs, followed by implementation of statistical process controls. The roles of various processing parameters including raw materials, pressing, and firing conditions (i.e., time, temperature, and pressure) are elucidated. For these devices, it was demonstrated that acceptable physical, mechanical, and dimensional properties were consistently obtained from carefully designed and statistically controlled processes.

Bioactive glasses with chemical composition 0.1 SiO2-0.2 CaO-0.2 Na2O-0.5 P2O5 have been prepared. The dielectric properties of the samples were measured in the frequency range from 100 Hz to 1 MHz and temperatures range from 100 to 370 K (Tg ≈ 400 K). The obtained data were analysed by the means of dielectric permittivity representation and modelled using the Havriliak–Negami equation. Various relaxation parameters were calculated with accuracy. Furthermore, investigation of the temperature dependence of their relaxation time using the Vogel– Tammam–Fulcher (VTF) model shows the weak interaction between alkali ions constituents and molecular networkformers for temperatures up to the glass transition.

Magnetic induction hyperthermia is emerging for cancer treatment with bioceramic materials rather radiotherapy and chemotherapy. Copper substituted cobalt ferrites as Co1-xCuxFe2O4 (where x=0.2, 0.4, 0.6, 0.8) ware prepared through self-propagating high-temperature synthesis (SHS) and the effect of copper on the structural, magnetic and biological properties was investigated. XRD revealed the formation of solid solution and the magnetic measurements showed the formation of soft ferrites as compared to CoFe2O4. The bioactive composite was prepared by incorporating the ferrite having optimum magnetic properties with bioactive glass and the constituent phases in the sintered composite were analyzed by X-ray diffraction (XRD). The bioactive composite comprised of Na2Ca2Si3O9 phase in solid solution. In vitro bioactivity of the composite was investigated in simulated body fluid (SBF) under physiological conditions. The precipitated hydroxy carbonated apatite (HCA) layer was confirmed by Fourier Transform Infra-Red spectrometer (FTIR), scanning electron microscopy (SEM) and XRD techniques. Cell viability and cytotoxicity against osteoblast MG63cell lines exhibit that the composite is cytocompatible.

The aim of the present investigation was to evaluate the role of TiO2+ZrO2 in the system of 45S5 bioactive glass for improving the bioactivity as well as other physical and mechanical properties of 45S5 bioactive glass. The partial substitution of 1,2,3 and 4 mol% of mixed TiO2+ZrO2 (3:2) for SiO2 in 45S5 bioactive glass system was done by melting route at 1400°Cin a globar rod furnace in air. A comparative study on structural and mechanical properties, as well as bioactivity of the glasses, was reported. The glass properties were determined by XRD, FTIR spectrometry, SEM and the bioactivity of the glass samples were evaluated by in vitro test in simulated body fluid (SBF). Density and compressive strength of glass samples were measured. Results indicate that with the partial substitution of TiO2+ZrO2 for SiO2 in 45S5 bioactive glass system, the mechanical properties of the glasses were found to increase significantly. The glass samples exhibited higher density and compressive strength as compared to their corresponding 45S5 bioactive glass. The in vitro studies of glass samples in SBF had shown that the pH of the solution increased with increasing the time period for immersion during the initial stage of the reaction. This indicated the bioactivity of the samples had increased with increasing duration. On later stages, the decrease in pH of the solution with time had shown that the bioactivity of the samples had decreased.

Recent developments from science and medical science show a growing interest in the anti-inflammatory activity of natural materials. Inflammation is the body’s physiologic response to injurious stimulation and is known to be mediated by various pro-inflammatory cytokines (e.g. TNF-α, IL-1β, IL-6 etc) and iNOS (inducible nitric oxide synthase). Quantum energy living body (QELBY) powder is a fusion of a special ceramic powder with natural clay mineral classified as quantum energy radiating material (QERM). The powder, composed mostly of silicon dioxide, is known to radiate reductive radiant energy. This study was designed to evaluate the anti-inflammatory activities of QELBY powder on RAW 264.7 mouse macrophage cells. QELBY powder was mixed with DMEM media and was allowed to stand for 48 hours. Afterwards, the supernatant was taken and diluted to various concentrations (0,5,10,20,40 μg/ml) prior to use. CCK-8 assay was done to determine the effects on cell viability. In addition, NO assay performed to elucidate the effect of QELBY on the NO production of LPS-stimulated macrophages. Lastly, RT-PCR and Western blot analysis for the detection of the mRNA and protein expressions, respectively, of proinflammatory cytokines and iNOS was made. Results demonstrated that QELBY powder causes both an increase in cell proliferation and a concentration-dependent decrease in NO production. Moreover, the mRNA and protein expressions of pro-inflammatory cytokines and iNOS were also inhibited. Taken together, these show that QELBY powder has anti-inflammatory activity and could therefore be used further in the development of materials that induce such kinds of benefits.

New ceramic composites from calcia-magnesia-silica system at a molar ratio of (CaO-MgO)/SiO2 closes to the unity and the addition of different amounts of zirconia (5 wt %, 15 wt % and 25 wt %) have been investigated. These systems powders were formed and fired at 1310 ± 20°C for 2 hr. Phase composition, microstructure, physical and mechanical properties of these composites were determined. The in-vitro bioactivities of these sintered composites were investigated by analysis of their ability for the formation of hydroxyapatite (HA) using SEM-EDS after their soaking in the simulated body fluid (SBF) for 7 days. The findings indicated that beginning of HA formation on the surface of all investigated composites. However, the composite containing 5 wt % ZrO2 gave clear tendency toward the formation-ability of HA typical to cauliflower morphology. The mechanical properties of the promised bioactive composite in term of Vickers hardness and fracture toughness were ~3 Gpa and ~2 Mpa. m1/2, respectively. The ceramic composite containing 5 wt % ZrO2 might be nominated to be implanted material because their property is quite similar to the properties of human cortical bone.

Introduction: Porcelain veneers are widely used in aesthetic prosthetic restoration of teeth in the anterior region. The application of dental porcelain facilitates obtaining excellent, natural-looking results with minimum invasive preparation of the tooth tissues. From both the mechanical and the aesthetic point of view, the strength and the durability of an adhesive bond depends on the correct conditioning of the luted surfaces and the polymerization procedure resulting in a high monomer conversion rate in the cement. Aim: The aim of this study was to measure the absorption of the intensity of curing light passing through samples of feldspar ceramic of various colors and thicknesses. Materials and methods: The study used disc-shaped samples prepared from Feldspathic porcelain. The diameter of each disc was 9.0 mm and their thickness ranged from 0.8 mm to 2.1 mm. Discs were prepared in different shades. The curing light intensity was measured for polymerization device Blue phase LED lamp (Ivoclar Vivadent, Liechtenstein) at a 1200 mW/cm2 light intensity (± 10%) and a wavelength ranging from 380 to 515 nm. Light intensity was measured using power gauge FieldMax (Coherent, USA). Results: Based on the measurements performed, it can be concluded that curing light intensity transmission decreases exponentially with the increase of the ceramic layer thickness. The results obtained indicated that the increase in color intensity and the decrease in ceramic brightness result in a reduction of the curing light transmission. Conclusion: To achieve adequate polymerization of the composite material placed beneath the restoration layer, the curing time should be adjusted according to the specified parameters.