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Abstract: A composite model of the mandible, constituted by an inner polymeric core and a glass fibre reinforced outer shell, has been developed and equipped with six ITI titanium implants and a full gold alloy arch bridge prosthesis. The effects of this oral rehabilitation on the biomechanics of the mandible are investigated through a simulation of the lateral component of the pterygoid muscles. These muscles are involved as the mouth is opened and closed, hence their activity is very frequent. An increase of the mandible stiffness due to the prosthesis is observed; moreover, the coupling of the relatively stiff rehabilitation devices with the natural tissue analogue leads to stress-shielding and stress-concentration in the incisal and molar regions, respectively. Although the amplitude of the force generated by pterygoid muscles is quite small, high strains over the incisal region are measured. A stress-shielding effect, of about 20%, is observed at the symphysis as the full arch bridge prosthesis is fixed on the implants. Therefore, the presence of the prosthesis leads to significant modification of the stress field experienced by the mandible, and this may be relevant in relation to the biomechanics of mandibular bone remodelling. [Copyright &y& Elsevier]

Abstract: Titanium dioxide (TiO2) and TiO2 glasses containing poly(ε-caprolactone) (PCL) up to 24% by weight were obtained by the sol–gel process. Powder compaction was achieved providing heat and pressure. Properties were evaluated through compression and bending tests assisted by X-ray micro-computed tomography imaging. The effects of compaction conditions (i.e. temperature, pressure and duration) on mechanical properties of inorganic/organic composites were investigated. Biocompatibility tests on organic/inorganic composites were carried out using human cells and the MTT assay to determine viability. Results indicated that the mechanical properties (i.e. Young''s modulus and maximum strength), in both compression and bending, were a function of the compression moulding conditions. Highest mechanical properties were measured using a compaction pressure of 1500MPa acting for 90min at a die temperature of 100°C. The results, however, also suggest that mechanical properties can be tailored by varying the amount of PCL to TiO2. Strength and stiffness spanned between the properties of spongy and cortical bone. Young''s modulus in both compression and bending were higher for PCL amounts of 6%. Instead, higher bending strength values were measured for PCL amounts of 12%. These weight amounts of PCL also provide higher average density values, thus suggesting that the polymeric phase is effective in toughening TiO2-based materials. The investigated materials also showed a very good cytocompatibility as indicated by the MTT assay results. [Copyright &y& Elsevier]

Hyaff 11®, a material derived from hyaluronic acid with interesting applications as a scaffold for tissue engineering, is made porous by salt leaching and mechanically tested in simple tension and confined compression. The tests revealed a different behavior in tension and compression, a feature common to other foamed materials. The difference between the behavior in tension and compression is such that the material cannot be modeled with a traditional constitutive law, thus an implicit constitutive equation valid for finite deformations is formulated, and a suitable selectivity criterion is proposed in order to distinguish the behavior in tension from that in compression. The results of the model are compared with the experimental findings both in simple tension and in confined compression, yielding a good fitting with five material parameters. [Copyright &y& Elsevier]

Abstract: Different formulations based on bioadhesive and biocompatible polymers, hydroxypropylmethylcellulose (HPMC), sodium hyaluronate (SH) and chitosan glutamate (CG), were prepared to be potentially used as ophthalmic viscosurgical device (OVD) during cataract surgery. Their rheological properties were analyzed in terms of flow and oscillation properties and compared to a commercially available OVD, widely employed in cataract surgery, named Viscoat®. All the formulations tested presented a pseudoplastic behavior during flow. Primary systems containing HPMC or CG and HPMC/CG binary systems behaved as viscous solution (G″>G′) over the range of oscillatory frequencies observed, while the primary systems containing SH and HPMC/SH binary formulations and showed an entangled network behavior when subjected to a sinusoidal stress. By increasing the SH concentration in the binary systems, the viscoelastic parameters, G′and G″, and zero frequency viscosity (derived from the Cross model) increased. Viscoat® presents viscoelastic parameters values lower than the corresponding values of all the binary formulations of HPMC/SH and higher than all the formulations made up of CG and HPMC. As regard to HPMC/SH binary system, the cross-over frequency decreased by increasing SH concentration in the systems and it was the highest for Viscoat® and thus the opposite occurred for the relaxation time. The rheological synergy in the binary formulations was assessed by calculating the interaction parameters which increased as a function of SH and CG concentration in the binary systems. The values of the interaction parameters of the formulations based on CG, are lower than 10Pa indicating that they did not interact synergically while the formulations based on SH show high values of the interactions parameters (in the range from 55 to 130Pa). This indicates that secondary bonds formation occurs between SH and HPMC. From the rheological analysis it can be concluded that the binary formulations based on CG do not possess appropriate features to be used as OVD while both the viscoelastic and the flow properties of the binary formulations made up of SH and HPMC are suitable for their application as OVD being able to maintain the ocular spaces and to be easily administrated. Moreover, thank to the adhesive properties of both components, the binary formulation should be able to interact with corneal endothelium so offering a durable protection to ocular tissue. On the basis of the rheological characterization presented in this work, we concluded that the binary system named VISC26 (HPMC at 0.8% and SH at 2.3%) represents the formulation that better fulfill the OVD requirements. [Copyright &y& Elsevier]

Abstract: The elimination of water from the body represents a fundamental therapeutic goal in those diseases in which oedemas occur. Aim of this work is the design of a material able to absorb large amount of water to be used, by oral administration, in those cases in which resistance to diuretics appears. Sorption and mechanical properties of the cellulose based superabsorbent hydrogel acting as a water elimination system have been modulated through the insertion of molecular spacers between the crosslinks. Starting polymers are the sodium salt of carboxymethylcellulose (CMCNa), a polyelectrolyte cellulose derivative, and the hydroxyethylcellulose (HEC), a non-polyelectrolyte derivative. Polyethyleneglycol (PEG) with various molecular weights, has been linked by its free ends at two divinylsulfone (DVS) crosslinker molecules, in order to increase the average distance between two crosslinking sites and thus acting as spacer. Both the effect of concentration and molecular weight of the spacer resulted to significantly affect the hydrogel final sorption properties and thus the efficiency of the body water elimination system. Biocompatibility studies have been performed to test the hydrogel compatibility with respect to intestinal and macrophages cell lines. To investigate the effects of intestinal cells conditioned media after the contact with the gel on macrophages nitric oxide release tests have been carried out. [Copyright &y& Elsevier]

Abstract: The photo-oxidative stability of polyamide 6,6 (PA 6,6) doped with a hindered amine light stabilizer (HALS) and a mixture of cupric chloride and potassium iodide was examined. Several analytical techniques were employed, in order to evaluate the correlation between chemical modifications, morphology and mechanical properties of PA 6,6 films irradiated at λ>300nm, 90°C, and 50% relative humidity. Infrared spectroscopy showed a build-up of carbonyl absorption in the range 1700–1780cm−1 due to primary and secondary photo-oxidation products. The increase in content of carbonyl groups was greatest in the case of the pure polymer, and it was also appreciable in the case of PA 6,6 stabilized with copper/KI system. On the other hand, the use of the HALS additive brought about a substantial increase in the amount of carboxylic acids formed. The morphology of the samples was found to have an effect on the kinetics of the accumulation of carbonyls, and it was observed that at a later stage of exposure the crystalline phase was also involved in the oxidation process. Tensile tests on films revealed a large reduction in ductility as a result of ageing for both neat polymer and HALS-doped polymer. Only a slight reduction in ductility was found for the polymer stabilized with the inorganic mixture. This study evidenced that the mixture of CuCl2 and KI has a far better long-term stabilizing efficiency in comparison with the HALS stabilizer. [Copyright &y& Elsevier]

Dentin bonding systems (DBS) have been developed in order to bond restorative materials (i.e. composite) to tooth tissues when function and integrity have to be re-established. Adhesion to dentin results from the penetration of DBS into the demineralised substrate constituted by a conditioned collagen network. The long-term stability of a restored tooth is mainly affected by the seal of the restorative material on the dental structures.Although leakage through the dentin–DBS interface has been widely reported, 3D investigation technique and accurate non-destructive measurements of leakage as functions of mechanical cycling have never been provided. To address these issues, the properties of the material interface are analysed using micro-tensile static and dynamic tests, assisted by the finite element modelling and by the X-ray computed micro-tomography. The dual energy absorption technique, with the synchrotron beam light, has been developed to investigate, in a non-destructive manner, the effect of mechanical cycling on leakage of a silver nitrate staining solution at the dentin–DBS interface.The effect of the pulpal roof on the stress distribution in the coronal dentin–DBS–composite interface has been investigated and the level at which the state of stress can be assumed to be uniform within acceptable limits has been defined.The tensile static and dynamic results suggest that the adhesive strength for the multi-step DBS resulted significantly higher than the other investigated DBS.Imaging results indicate that 3D leakage occurs radially at the dentin–adhesive interface through the interface itself rather than through the unconditioned dentin bulk; moreover, the dynamic tensile loading allows a more diffuse staining penetration. [Copyright &y& Elsevier]

Abstract: Nanocomposites based on biodegradable poly(ε-caprolactone), (PCL) and organically modified layered silicates (organoclay) were prepared by melt mixing. The isothermal crystallization of PCL/clay nanocomposites at different clay concentrations (from 0.1 to 10wt%) were investigated by differential scanning calorimetry (DSC) and rheometry in dynamic tests. The results showed that the well dispersed organoclay platelets acted as nucleating agents in the PCL matrix, as confirmed by a remarkable reduction of the crystallization half-time, t1/2. This effect was most pronounced at very low clay concentrations. In particular, in composites with 0.4% of clay, t1/2 was one order of magnitude lower than the pure polymer. The heating thermograms, performed on PCL and on PCL/clay after isothermal crystallization showed a reduction of the melting temperature with the increase of the clay content, suggesting that the degree of perfection of the crystals and the degree of crystallinity were affected by the restricted mobility of the chains, which did not allow the growth of well developed lamellar crystals. The rheological measurements confirmed the effect of clay on crystallization kinetics. The evolution of G′ and G″ vs. time was correlated to the clay concentration and to the development of the crystalline phase during isothermal experiments. [Copyright &y& Elsevier]

• CMC-HEC aerogels were synthetized and dried using a supercritical assisted process. • A solvent exchange starting from 50 % v/v ethanol preserved the native gel nanofibrous morphology. • A swelling ratio (SR) up to 500 was measured for these CMC-HEC aerogels. Superabsorbent polymers (SAPs) are organic materials possessing high capacity to absorb and retain large volumes of water, saline and physiological solutions (at least 10–20 times their weight). The most commonly used SAPs are acrylated-based polymers that are not biodegradable or recyclable. To overcome these limits, carboxymethylcellulose (CMC) with hydroxyethylcellulose (HEC) hydrogels were synthetized in this work and dried using a supercritical assisted process at 200 bar and 45 °C. The solvent exchange procedure influenced the final aerogel morphology and, thus, the aerogel swelling ratio (SR). A solvent exchange starting from 50 % v/v ethanol, preserved the native gel nanofibrous morphology, producing a SR up to 20 times larger than the ones reported in the literature using the same process, corresponding to a water uptake larger than 500 times the weight of the dried aerogel. [ABSTRACT FROM AUTHOR]

An abstract of the article "Adenoviral Vector-Mediated Expression of Bone Morphogenetic Protein-4 in Mesenchymal Stem Cells Induces Differentiation into the Osteoblastic Lineage and Bone Production In Vivo," by Barbara Lombardo and colleagues is presented.