Physicochemical characterization of biomaterials commonly used in dentistry as bone substitutes--comparison with human bone

The present work focuses on the physicochemical characterization of selected mineral-based biomaterials that are frequently used in dental applications. The selected materials are commercially available as granules from different biological origins: bovine, porcine, and coralline. Natural and calcined human bone were used for comparison purposes. Besides a classical rationalization of chemical composition and crystallinity, a major emphasis was placed on the measurement of various morphostructural properties such as particle size, porosity, density, and specific surface area. Such properties are crucial to acquiring a full interpretation of the in vivo performance. The studied samples exhibited distinct particle sizes (between 200 and 1000 microm) and shapes. Mercury intrusion revealed not only that the total sample porosity varied considerably (33% for OsteoBiol, 50% for PepGen P-15, and 60% for BioOss) but also that a significant percentage of that porosity corresponded to submicron pores. Biocoral was not analyzed by this technique as it possesses larger pores than those of the porosimeter upper limit. The density values determined for the calcined samples were close to the theoretical values of hydroxyapatite. However, the values for the collagenated samples were lower, in accordance with their lower mineral content. The specific surface areas ranged from less than 1 m(2)/g (Biocoral) up to 60 m(2)/g (BioOss). The chemical and phase composition of most of the samples, the exception being Biocoral (aragonite), were hydroxyapatite based. Nonetheless, the samples exhibited different organic material content as a consequence of the distinct heat treatments that each had received

Stability of Biaxial Nematic Phase for Systems with Variable Molecular Shape Anisotropy

We study the influence of fluctuations in molecular shape on the stability of the biaxial nematic phase by generalizing the mean field model of Mulder and Ruijgrok [Physica A {\bf 113}, 145 (1982)]. We limit ourselves to the case when the molecular shape anisotropy, represented by the alignment tensor, is a random variable of an annealed type. A prototype of such behavior can be found in lyotropic systems - a mixture of potassium laurate, 1-decanol, and $D_2O$, where distribution of the micellar shape adjusts to actual equilibrium conditions. Further examples of materials with the biaxial nematic phase, where molecular shape is subject to fluctuations, are thermotropic materials composed of flexible trimeric- or tetrapod-like molecular units. Our calculations show that the Gaussian equilibrium distribution of the variables describing molecular shape (dispersion force) anisotropy gives rise to new classes of the phase diagrams, absent in the original model. Depending on properties of the shape fluctuations, the stability of the biaxial nematic phase can be either enhanced or depressed, relative to the uniaxial nematic phases. In the former case the splitting of the Landau point into two triple points with a direct phase transition line from isotropic to biaxial phase is observed.Comment: 18 pages containing 6 figure

Chronic Recurrent Multifocal Osteomyelitis: A Case Report with Atypical Presentation.

INTRODUCTION: Chronic recurrent multifocal osteomyelitis (CRMO) is a rare autoinflammatory condition. The clinical picture consists of sterile osteomyelitis, typically with multiple-site lesions in the metaphysis of long bones and not uncommonly, symmetrical bone involvement. It is a poorly understood entity, whose prognosis, etiology and ideal treatment are still controversial. The authors report a case of unifocal presentation with an atypical location. CASE REPORT: A previously healthy 12-year-old Caucasian girl came to our institution due to progressive pain on her left thigh for the previous 3 months. The initial X-ray showed a permeative, diaphyseal lesion of her left femur, with marked periosteal reaction. The differential initially included Ewing's sarcoma, osteosarcoma, subacute osteomyelitis, and Langerhans cell histiocytosis. Needle and open biopsies demonstrated the presence of chronic inflammatory infiltrate, with fibrosis, but no signs of neoplastic disease. Serologic and microbiological studies failed to demonstrate an infectious etiology. The patient was treated with nonsteroid anti-inflammatories, corticosteroids, and bisphosphonates for 6 months. Although no antibiotics were employed, the patient showed clinical and radiological improvement, at 18-month follow-up. CONCLUSIONS: CRMO is a rare condition, and the absence of specific features constitutes a diagnostic challenge. A high level of suspicion is paramount to avoid unnecessary biopsies and repeated antibiotic regimens. Unifocal presentation of this disease, atypical locations, and absence of recurrence have all been previously reported, with the evidence pointing to a shared etiological process with no distinction being made between these variants. For this reason, the authors believe that the term "nonbacterial osteomyelitis" might be a more all-embracing designation.info:eu-repo/semantics/publishedVersio

Wage differentials within a female dominated occupation: domestic workers in informal and flexible jobs in Portugal

We use an original dataset to examine the impact of informal and flexible contractual arrangements on wages of a sample of domestic workers hired by private employers in Portugal. All arrangements should be formal involving declaration of employment relationship to social security authorities. Our results suggest formality benefits workers whether they have stable or flexible contract. However, social and labour market processes help shape and maintain inequality, especially for migrant workers. Specific and general skills are undervalued and are unable to generate rewards. Compensation was identified for contingent work, multiple employers and elderly caregivers but this hides exploitation and insecurity.info:eu-repo/semantics/acceptedVersio

Grain boundary Fe-doping effects in LSGM

The electrical properties of La0.95Sr0.05Ga0.90Mg0.10O3 ? ? (LSGM) were modified by selective doping of the grain boundaries, using LaFeO3 screen-printed layers and annealing at high temperature to promote Fe diffusion into LSGM. Scanning electron microscopy (SEM) and energydispersive spectroscopy (EDS) analyses showed that iron was mainly located along the grain boundaries with the bulk grain composition almost unchanged. Impedance spectra showed a significant increase in the total conductivity for the Fe-doped samples, the effect being greater for the grain boundary contribution. The formation of a parallel pathway for electronic conduction along the grain boundaries explains these effects. Ageing of these samples at high temperature, after removal of the Fe source, showed a steady shift to the original LSGM behaviour, due to dilution of Fe throughout the samples.371C-9F16-EBDE | Eduarda GomesN/

Processing and electrical conductivity of lanthanum gallate core-shell heterostructures

The electrical properties of a lanthanum gallate solid electrolyte were modified by selectively doping the grain boundaries with Fe. This was achieved by sandwiching a La0.95Sr0.05Ga0.90Mg0.10O3-? (LSGM) dense pellet between LaFeO3 samples. Annealing at 1550?C in air for several hours promoted Fe diffusion into LSGM via the grain boundaries. Scanning electron microscopy and energy-dispersive spectroscopy analyses showed that iron was located at the grain boundary while the grain bulk preserved the LSGM composition. Impedance spectra obtained at low temperature consist of the two usual bulk and grain boundary contributions. A significant increase in total conductivity was observed for the iron-doped samples, the effect being greater for the grain boundary contribution. The total conductivity measured for the iron-containing material revealed a slight decrease with decreasing oxygen partial pressure, suggesting the onset of p-type electronic conduction. Estimates of the p-type electronic conductivity (?p) were obtained by fitting the low temperature impedance spectra to a simple equivalent circuit including one parallel electronic branch. The value for ?p in air at 300?C is 3.1?10-6 S/cm and the activation energy is 75.1 kJ/mol between 300 and 400?C.371C-9F16-EBDE | Eduarda GomesN/

Mixed conduction induced by grain boundary engineering

Mixed oxygen-ion electronic conductors were prepared starting from the well-established solid lectrolyte La0.95Sr0.05Ga0.90Mg0.10O3?? (LSGM). The adopted strategy involved selective grain boundary doping with iron to form a grain boundary region with high electronic conductivity. Scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS), impedance spectroscopy in air (around 300 ?C) and high temperature (700?800 ?C) ac conductivity measurements as a function of pO2 all suggest that this doping strategy was successful. In fact, on increasing the Fe-dopant level, Fe always concentrated along the grain boundary region (as confirmed by SEM/EDS), the total conductivity increased and each individual impedance arc decreased, in agreement with predictions based on the presence of a parallel pathway for electronic transport. Furthermore, the increase in total conductivity (?) with dopant level showed a positive log ? versus log pO2 dependence, typical of hole conductivity.371C-9F16-EBDE | Eduarda GomesN/

Microstructural effects on the electrical properties of grain boundary Fe-doped LSGM

Mixed conductors based on grain boundary Fe-doped La0.95Sr0.05Ga0.90Mg0.10O3 ? ? (LSGM) ceramics were obtained by selectively doping the grain boundaries with Fe. This was achieved using LaFeO3 ? ? layers screen-printed onto LSGM, after annealing at high temperature in air for several hours to promote Fe diffusion into LSGM. The influence of the number of impregnation cycles, temperature of impregnation and microstructure of the host LSGM was evaluated by impedance spectroscopy and oxygen permeability. The impedance spectra consist of high and low frequency semicircles, ascribed to bulk and grain boundaries. The amplitude of both contributions decreases with increasing impregnation temperature and time, suggesting the onset of electronic conduction along grain boundaries. The effect is stronger for ceramics with larger grain size. The observed trends are fully consistent with estimates of p-type electronic conductivity obtained from oxygen permeability measurements using a simplified electrochemical cell.371C-9F16-EBDE | Eduarda GomesN/

Influence of hydrochloric acid concentration on the demineralization of cortical bone

Although demineralized bone matrix has been considered a successful grafting material, combining both osteoconductive and osteoinductive properties, conflicting results have been published in the literature regarding its bone-inducing abilities. This may be a consequence of following different demineralization procedures that naturally result in products with different properties. The present work examines the evaluation of the demineralization process of similar samples of human cortical bone using three different concentrations of hydrochloric acid solutions (0.6 M, 1.2 M and 2.4 M). Sample calcium content was determined (by Atomic Absorption Spectroscopy) at various immersion times, allowing the construction of the corresponding kinetic profiles. Phase and chemical composition were enabled by X-Ray Diffraction Spectroscopy and Fourier Transform Infrared Analysis, respectively. Structural modifications were followed by Light and Scanning Electron Microscopy and quantified by mercury porosimetry (in terms of porosity and pore size distribution). As expected, increasing the acid concentration led to an increase in the demineralization rate, but not in a proportional way. However, one of the most significant effects of the acid concentration was found on the sample structural features. In fact, a considerable increment in porosity was detected for the sample subjected to the highest hydrochloric acid concentration. Microscopic observations demonstrated that despite the structural deformation resultant from demineralization, the basic microstructure was preserved