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Biomaterials are routinely used in dentistry for tissue engineering. The purpose of the present work is to compare the performance of a new alloplastic biomaterial (Blue-Bone®), xenogeneic biomaterial (Bio-Oss®), and a mixture of both biomaterials with 50% of autogenous bone. 32 Wistar rats underwent a surgical procedure in which a circular disc of bone was removed from the calvaria with a trephine drill 10 mm in diameter to create a critical bone defect, which was filled with the biomaterials under study. After 40 days, the animals were euthanized and the calvaria was removed for processing and analysis. Histomorphometric determination of vital mineralized tissue (VMT), no-vital mineralized tissue (NVMT), and on-mineralized tissue (NVMT) was performed. The results showed that, while Bio-Oss® had the best performance when used in conjunction with autogenous bone, the addition of autogenous bone did not significantly improve Blue-Bone® performance.

Dental implant treatment requires an available bone volume in the implantation site to ensure the implant’s mechanical stability. When the bone volume is insufficient, one must resort to surgical means such as guided bone regeneration (GBR). In GBR surgery, bone grafts and membranes are used. The objective of this work is to manufacture and characterize the in vitro and in vivo properties of resorbable collagen type I membranes (Green Membrane®) for GBR. Membrane surface morphology was characterized by SEM and roughness was measured using an interferometric noncontact 3D system. In vivo skin sensitization and toxicity tests have been performed on Wistar rats. Bone defects were prepared in 24 adult male rats, filled with biomaterials (Blue Bone® and Bio Oss®) and covered with collagen membranes to maintain the mechanical stability of the site for bone regeneration. The incisions were closed with simple stitches; and 60 days after the surgery, the animals were euthanized. Results showed that the analyzed membrane was homogeneous, with collagen fiber webs and open pores. It had no sign of cytotoxicity and the cells at the insertion site showed no bone morphological changes. There was no tissue reaction and no statistical difference between Blue Bone® and Bio Oss® groups. The proposed membrane has no cytotoxicity and displays a biocompatibility profile that makes it suitable for GBR.

Titanium alloys have been widely used as biomaterials. However, contact of titanium with body fluids can release toxic ions due to degradation. The present work aimed to compare the wettability and corrosion resistance of two Ti alloys without toxic ions, Ti–30Nb–7Zr (TNZ) and Ti–47Nb (TN), with those of the commercial biomedical alloy Ti–6Al–4V-ELI (ASTM F136). Corrosion studies were carried out in a three-electrode cell conventional system, which Ti alloys as working electrodes were exposed to 0.9% sodium chloride electrolyte at 37 °C to determine if they have surface properties adequate for biomedical applications. α and β phases present on the microstructure were distinguished using scanning electron microscopy (SEM). Chemical surface composition was performed using X-ray photoelectron spectroscopy (XPS) analysis. Surface energy was determined by wettability testing. For TN and TNZ alloys the microstructure consisted of a β matrix, although only TNZ exhibited α precipitates. In contrast, F136 alloy microstructure presents α matrix, which was strengthened by the β phase. All alloys tested exhibited an increase in corrosion potential with the immersion time, indicating the growth and stabilization of the passive oxide film. The results showed that ASTM F136 is more hydrophilic but less corrosion resistant than the TN and TNZ alloys. It remains to be seen in practical applications whether the lower hydrophobicity of TN and TNZ alloys is compensated by lower toxicity and higher corrosion resistance.

In this work, in vitro testing was used to study the properties of non-crosslinked type 1 bovine derived collagen membranes used in bone regeneration surgery. Collagen membranes were prepared, their surface roughness was quantified by interferometry, their morphology was observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), their wettability was measured by the contact angle technique, their mechanical properties were investigated by tensile testing, their phase transformation temperatures were measured by Differential Scanning Calorimetry (DSC), and their biocompatibility was evaluated by immunological testing. The calorimetry tests showed that the membrane is formed only by type 1 collagen. The SEM observations showed that the morphology consists of layers of highly organized collagen fibers and patterns of striated fibrils typical of type 1 collagen. The small contact angle showed that the membrane is hydrophilic, with the possibility of rapid absorption of body fluids. The tensile tests showed that the membrane has enough elasticity, ductility, and mechanical strength for use in tissue regeneration. With the immunostaining technique, it was possible to confirm the membrane biocompatibility.

The aim of this work was to analyze the properties and shear bond strength (SBS) of lithium disilicate to resin cement before and after etching the glass-ceramic surfaces. Lithium-metasilicate samples were heat treated and characterized by Scanning Electron Microscopy, X-ray diffraction and roughness measurement. For the analysis of the shear bonding strength (SBS) of lithium disilicate to dental resin cement, three groups (n = 12) of Li2Si2O5 were prepared: 1°)without treatment (NT); 2°)surface etching with hydrofluoric acid(HF), followed by silane agent and adhesive treatment; 3°) surface treatment with a self-etching ceramic primer (SECP). After the heat-treatment, the samples had Li2Si2O5 crystalline phase dispersed in a residual amorphous phase. Roughness of the NT and SECP samples was smaller that of the HF samples. Samples without surface treatment (NT) had the lowest SBS (5.5MPa). HF(24.2MPa) and SECP(24.8MPa) samples has similar SBS. Weibull statistics showed that HF-samples are more reliable than NT and SECP. The SBS was significantly increased by either HF etching and SECP surface treatment. While the chemical characteristics of the surface submitted to SECP treatment are considered to be responsible for the SBS increase, the main adhesion mechanism after HF etching is the increase in surface roughness.

High hydrostatic pressure (HHP) stress generates cellular responses similar to those to other stresses that yeasts endure in fermentation tanks. Structural and spatial compaction of molecules, as well as weakening and stretching of plasma membranes and cell walls, are often observed and have a significant influence on the fermentative process. Atomic force microscopy (AFM) yields accurate data on the morphological characteristics of yeast cell walls, providing important insights for the development of more productive yeast strains. Saccharomyces cerevisiae cell wall assessment using AFM in the intermittent contact reading mode using a silicon cantilever, before and after application of a pressure of 100 MPa for 30 min, demonstrated that mother and daughter cells have different responses. Daughter cells were more sensitive to the effects of HHP, presenting lower average Ra (arithmetic roughness), Rz (ten-point average roughness), and Rq (root-mean-square roughness) after exposure to high pressure. Better adaptation to stress in mother cells leads to higher cell wall resistance and, therefore, to better protection.

Commercially pure titanium (Ti G2 and Ti G4) and the Ti–6Al–4V (Ti G5) alloy have limitations for biomedical applications, due to either low mechanical strength (Ti G2, Ti G4) or the possible release of toxic ions (Ti G5). Since Ti alloys have a low hardening coefficient, it is very difficult to improve their mechanical properties by work hardening. The purpose of this work was to compare the mechanical and clinical properties of Ti G4 nanostructured after severe plastic deformation by ECAP (Ti G4 Hard) with those of Ti G2, Ti G4 and Ti G5. Bars, disks and dental implants made with Ti G2, Ti G4, Ti G5 and Ti G4 Hard were tested. Mechanical tests (tension, compression, hardness, elastic modulus, fatigue and torque) and roughness measurements were performed. The results of the mechanical tests showed that Ti G4 Hard has a higher mechanical strength and a lower elastic modulus than Ti G2, Ti G4 and Ti G5. Scanning electron microscopy and roughness measurements results showed that acid etched Ti G4 Hard nanostructured has better surface morphological features than Ti G2, Ti G4 and Ti G5. The clinical performances of Ti G4 and Ti G4 Hard were similar. The high mechanical strength of Ti G4 Hard means that it can be used to replace Ti G5 in several clinical applications, with the advantage of not releasing toxic ions. The Ti G4 Hard dental implants have adequate mechanical properties and can be inserted in areas with low bone volume. Keywords: Titanium, High strength cp Ti, Strain hardening, Ti nanostructured, Dental implant, ECAP

Manganese ferrite (MnFe2O4) nanoparticles were dispersed in paraffin and the physical properties of this composite were investigated by X-ray diffraction (XRD), ferromagnetic resonance (FMR), vibrating sample magnetometry (VSM), field cooled (FC) and zero field cooled (ZFC) curves and Mössbauer spectroscopy. The results showed that dispersion in moderate quantities of paraffin significantly increases the crystallite size, the absolute value of the anisotropy field, the saturation magnetization and the blocking temperature of the nanoparticles, a result that may be of interest for practical applications of the composite. Keywords: Manganese ferrite, Paraffin, Nanoparticles, Composites

A nanostructured Cr11Ge19 phase was produced by mechanical alloying for 15 h. Decomposition occurred for larger milling times, yielding Cr, Ge, Cr2O3 and GeO2. According to the Cr-Ge phase diagram, the Cr11Ge19 phase is stable up to ≈ 928 oC, but, when submitted to milling, a structural instability causes its decomposition. We studied this structural instability using the coordination numbers and interatomic distances of bulk Cr11Ge19 to simulate the structure factors SCrCr(K), SCrGe(K), and SGeGe(K). The radial distribution functions RDFCrCr(R), RDFCrGe(R) and RDFGeGe(R) were obtained by Fourier transforming the Sij(K) factors, and an important chemical disorder up to ≈7 Å was observed in the RDFCrGe(R) and RDFGeGe(R) functions. This chemical disorder was quantified using Cowley-Warren α ij CW parameter. The thermoelectric properties of the Cr11Ge19 phase were also studied.

In a recently proposed model, the magnetocrystalline anisotropy of a mixed ferrite is assumed to be the weighted average of the contributions of the anisotropies of Fe3+ and M2+ ions in A and B sites. In the present work, this model is used to study the cation distribution, saturation magnetization and magnetocrystalline anisotropy of nickel-aluminum ferrite nanoparticles using ferromagnetic resonance data. The experimental results show that the saturation magnetization decreases continuously with aluminum addition, that the magnetocrystalline anisotropy is maximum when 10% of the Fe ions are replaced by Al ions and that replacement of 50% of the Fe ions by Al ions is enough to reduce the saturation magnetization and the magnetocrystalline anisotropy of the mixed ferrite NiAlxFe2-xO4 to almost zero. This is consistent with the findings of other researchers, obtained by different methods.

The energy absorption in ballistic tests of alumina-ultra high molecular weight polyethylene (UHMWPE) composites with 60, 80 and 90 wt% alumina submitted to gamma radiation doses of 25, 50 and 75 kGy was investigated. The ballistic tests were carried out at subsonic speed using a compressed air system. The results showed that the composite with 80% alumina irradiated with 50 kGy yields the best ballistic results. Gel content, Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) results showed that this composite is the one with the highest concentration of crosslinks and the lowest volume fraction of amorphous UHMWPE. Scanning electron microscopy (SEM) images of the same composite showed a high pullout, suggesting that gamma irradiation increases the adhesion between alumina and UHMWPE.

Nanosized particles of Ni 1− x Co x Fe 2 O 4 were synthesized by the sol–gel combustion method and the physical properties of these mixed ferrites were studied by X-ray diffraction and ferromagnetic resonance. The average crystallite size in samples with different Ni–Co ratios was determined from the X-ray diffractograms, whereas ferromagnetic resonance spectra were used to study the dependence of the magnetocrystalline anisotropy on the relative concentration of nickel and cobalt. According to the X-ray diffractograms, the samples are single phase and the crystallite size is between 9 and 22 nm. The ferromagnetic resonance spectra showed that the magnetocrystalline anisotropy of the samples is positive, except for pure NiFe 2 O 4 , and increases monotonically with Co concentration, a result that could be of interest for practical applications.

The response to ballistic impact of alumina-ultra high molecular weight polyethylene (UHMWPE) composites with different relative concentrations of alumina was investigated. The impact tests were carried out at subsonic speed using a compressed air system. The results showed that the depth of penetration (DOP) in a Medium Density Fiberboard (MDF) bulkhead protected by a disk of the composite decreased with increasing concentration of alumina in the composite. Scanning electron microscopy (SEM) images of composites with 80 %, 85 % and 95 % alumina showed transgranular, intergranular and ductile fracture mechanisms.

A nanostructured SnTe phase was produced by mechanical alloying after 2 h of milling. Part of the as-milled powder was annealed and its X-ray diffraction (XRD) pattern was recorded. The XRD patterns of the as-milled and annealed samples were refined using the Rietveld method. After annealing, partial decomposition of the SnTe phase was observed and corroborated by estimating the mean crystallite size using a Willianson-Hall plot. The Cowley-Warren parameter α SnTe CWfor the first coordination shell was calculated, showing a preference for homopolar pairs. This preference is consistent with the partial decomposition observed. According to the optical absorbance spectra, the band gap energy is inversely proportional to crystallite size, following a decaying exponential function. From the photoacoustic absorption spectroscopy measurements, the thermal diffusivity parameter and the transport properties of as-milled and annealed SnTe powder were determined.

The mechanical, chemical, roughness and wettability properties of 70/30 poly (L,DL-lactide acid) three-dimensional (3D)-printed surgical plates made with extruded polymer filaments developed in the first part of this work were investigated. The plates were printed with horizontal (HRZ) and vertical (VRT) running layer orientations and evaluated by tensile, Fourier transform infrared (FTIR), optical perfilometry and wettability tests before and after degradation in simulated body fluid (SBF) for 21 days. The results show that the ultimate tensile strength (UTS) of HRZ plates before immersion in SBF was higher (34.1 MPa) than that of VRT plates (31.8 MPa). The Young’s modulus (E) of HRZ plates and VRT plates are similar (4 GPa). After immersion in SBF, the UTS of HRZ plates dropped to 20.5 MPa and E decreased to 3.3 GPa. VRT were not tested after SBF immersion due to the large degradation. FTIR analysis showed no evidence of chemical change in the plates after immersion in SBF. The roughness parameter R3z of VRT surfaces (19.54 µm) was higher than that of the HRZ surfaces (12.80 µm). The roughness parameters increased after degradation in SBF (p = 0.7048). The contact angles of HRZ surfaces before immersion in SBF (66.28°) were higher than after immersion in SBF (18.12°); the same behavior was also observed in VRT plates. Refereed/Peer-reviewed

A recently proposed model, based on the relative occupancy of tetrahedral and octahedral sites by different cations, was used to study the magnetocrystalline anisotropy of mixed Ni–Zn ferrite nanoparticles. According to this model, the total magnetocrystalline anisotropy is the weighted average of the contributions of the anisotropies of Fe 3+ and M 2+ ions in A and B sites. The model predictions are confirmed in the case of nickel–zinc ferrite.

The ball milling process was used to obtain nanocrystalline cubic silicon. Between 5 and 10 h of milling, amorphous silicon was also formed. The differential scanning calorimetry (DSC) spectrum of a powder milled for 10 h showed that the amorphous–crystalline phase transition occurs at about 450 °C. According to Raman spectroscopy and X-ray diffraction results, volume fractions of the crystalline, interfacial and amorphous phases were about 30, 39 and 31%, respectively. Copyright © 2010 John Wiley & Sons, Ltd.

Electron magnetic resonance (EMR) line widths of Mn 2+ in CdO were measured in samples doped with small concentrations (up to 1.0 mol%) of Mn. The line width of one of the lines, which corresponds to the |1/2 1/2>↔|−1/2 1/2> transition, was found to change in a predictable way with Mn concentration, according to the theoretical equation Δ H pp =2.05+370 f (1− f ) 42 , where Δ H pp is the line width in mT and f is the Mn concentration in mol%. The experimental results show that the technique can be used to measure, rapidly and nondestructively, small concentrations of Mn in commercial CdO.

Ultra-high molecular weight polyethylene (UHMWPE) is used in the manufacture of medical applications due to its excellent mechanical properties, abrasion resistance and biocompatibility. The products are usually sterilized by gamma radiation. It is well known that gamma irradiation introduces structural changes that may be detrimental to the integrity and performance of the polymer, limiting its useful life. Therefore, it is imperative to have a fundamental understanding of the fracture behaviour of the material. A commercial general grade ultra-high molecular weight polyethylene (UHMWPE) was irradiated with several total doses and the effects of gamma radiation on the mechanical behaviour of the polymer and its morphology were evaluated by tensile tests, electron spin resonance spectroscopy (ESR) and scanning electron microscopy (SEM). The experimental data show that the gamma irradiation changes the molecular structure of UHMWPE, degrades its tensile properties and produces a gradual ductile-to-brittle transition.

Knowledge of particle size distribution is very important for the study of magnetic fluids, magnetic powders and other magnetic systems. In this work, we describe a simple method for its determination from FMR measurements. The method was applied to the case of MgFe2O4 precipitates in (Mg,Fe)O.

Nanocrystalline particles of magnesioferrite (MgFe2O4) were prepared by a sol-gel/combustion method using iron nitrate, Fe(NO3)3.9H2O, magnesium nitrate, Mg(NO3)2.6H2O, and citric acid, C6H8O7.H2 O, and annealed for 2 hours at 400, 500 and 600 °C. The average particle size, determined by X ray diffraction, was found to depend on the annealing temperature and varied from 〈D〉 = 8.1 to 〈D〉 = 17.8 nm. By measuring at several temperatures the relative intensity of the Mössbauer spectra due to superparamagnetic particles and to ferrimagnetic particles, we determined the size distribution of the nanoparticles in the samples. It was found to be a log-normal distribution with a most probable diameter that varied from Dm = 6.4 to 17.2 nm and a full width at half-height ΔD in the 5-6 nm range.

Electron magnetic resonance linewidths of Gd3+ in ceria and magnesia were measured in samples doped with small concentrations (up to 1.0 mol%) of Gd. The linewidth was found to change in a predictable way with Gd concentration. The experimental results show that the technique can be used to measure, rapidly and nondestructively, small concentrations of Gd in commercial CeO2 and MgO.

Introduction Our purpose was to study the mechanical properties and phase transformations of orthodontic wires submitted to in-vivo exposure in the mouth for different periods of time. Methods Stainless steel wires were tied to fixed orthodontic appliances of 30 patients from the orthodontics clinic of Universidade Federal do Rio de Janeiro School of Dentistry in Brazil. According to the duration of the clinical treatment, the patients were divided into 3 groups. After in-vivo exposure, the samples were studied by mechanical testing (torsion) and ferromagnetic resonance. Statistical analyses were carried out to evaluate the correlation between time of exposure, mechanical properties, and austenite-to-martensite transformation among the groups. Results The results were compared with as-received control samples. The torque values increased as time in the mouth increased. The increase in torque resistance showed high correlations with time of exposure ( P = 0.005) and austenite-martensite phase transformation. Conclusions The resistance of stainless steel orthodontic wires increases as the time in the mouth increases; this effect is attributed to the austenite-to-martensite transformation.