Search

Ultrafine-grained (UFG) commercially pure (Ti Grade 2) and high-purity (Ti 99.99%) titanium can be a good alternative to less biocompatible Ti alloys in many biomedical applications. Their severe plastic deformation may lead to a substantial increase of strength, but their highly refined microstructure show a lower thermal stability which may limit their range of applications. The purpose of this study was to investigate the effect of interstitial elements on the thermal stability of UFG Ti Grade 2 and high-purity Ti 99.99% processed by a multi-pass cold rolling to the total thickness reduction of 90%. The severely cold rolled Ti sheets were annealed at temperature in the range of 100–600 °C for 1 h and, subsequently, they were evaluated in terms of microstructure stability, mechanical performance as well as heat effects measured by differential scanning calorimetry (DSC). It was found that the microstructure and mechanical properties were relatively stable up to 200 and 400 °C in the case of UFG Ti 99.99% and Ti Grade 2, respectively. DSC measurements confirmed the aforementioned results about lower temperature of recovery and recrystallization processes in the high-purity titanium. Surprisingly, the discontinuous yielding phenomenon occurred in both investigated materials after annealing above their thermal stability range, which was further discussed based on their microstructural characteristics. Additionally, the so-called hardening by annealing effect was observed within their thermal stability range (i.e., at 100–400 °C for UFG Ti Grade 2 and 100 °C for UFG Ti 99.99%).

Two approaches can be taken when designing properties of the native oxide layers formed on Ti-based biomedical materials: (i) changing the chemical composition of the substrate by adding biocompatible, valve alloying elements, and (ii) changing the microstructure of the substrate—especially its level of defectiveness—through large plastic deformation. However, especially in the aggressive fluoridated oral environment, it is still unknown what factor is more effective in terms of enhancing oxide layer protectiveness against biocorrosion: (i) the presence of valve alloying elements, or (ii) a high number of structural defects. To gain knowledge about the separate influence of both of these factors, surface properties were examined for commercially pure Ti and Ti–Nb–Ta–Zr alloy in microcrystalline state as well as after multiple-pass cold rolling, a process that can be readily scaled up to the industrial level. This study showed that while valve-alloying elements and structural defects individually have a beneficial effect on Ti oxide layer properties in fluoridated medium, they not have to act in a synergistic manner. These findings have to be taken into account when designing future Ti-based dental materials together with analyzing their mechanical performance with respect to mechanical strength and elastic properties.

The metabolization of carbohydrates by Streptococcus mutans leads to the formation of lactic acid in the oral cavity, which can consequently accelerate the degradation of dental implants fabricated from commercially available microcrystalline Ti. Microstructure influences surface topography and hence interaction between bacteria cells and Ti surfaces. This work offers the first description of the effect of S. mutans on the surface topography and properties of nanostructured bulk Ti, which is a promising candidate for modern narrow dental implants owing to its superior mechanical strength. It was found that S. mutans incubation resulted in the slight, unexpected decrease of surface nanoroughness, which was previously developed owing to privileged oxidation in areas of closely spaced boundaries. However, despite the changes in nanoscale surface topography, bacteria incubation did not reduce the high level of protection afforded by the oxide layer formed on the nanostructured Ti surface. The results highlight the need–hitherto ignored–to consider Ti microstructure when analyzing its behavior in the presence of carbohydrate-metabolizing bacteria.

The cervical spine can be affected by many types of inflammatory arthropathies, and the most common autoimmune diseases with cervical spine involvement are rheumatoid arthritis (RA), spondyloarthritis (SpA), and juvenile idiopathic arthritis (JIA). The clinical symptoms of cervical spine pathologies are often nonspecific or absent; therefore, imaging plays a crucial diagnostic role. RA is the most prevalent autoimmune disease; it often leads to cervical spine instability and subsequent myelopathy. In SpA, due to new bone formation, the characteristic lesions include syndesmophytes, parasyndesmophytes, and bone ankylosis, but instabilities are rare. In JIA, early apophyseal bone ankylosis is characteristic, in addition to impaired spinal growth. The aim of this review article is to discuss the imaging pathologies found in patients with RA, SpA, and JIA in the early and advanced stages. This knowledge would be helpful in the proper diagnosis and treatment of these diseases.

Scleroderma is a rare, autoimmune, chronic condition that affects the connective tissue by excessive collagen production. If diagnosed before the age of 16, it is referred to as juvenile scleroderma. There are two major types of the condition: localized and generalized scleroderma. Localized scleroderma has a much higher incidence than the generalized type which is extremely rare among children and affects mostly adults. In either case, imaging can prove to be useful in both the diagnosis and monitoring of the disease. In this article, we aim to review the imaging findings that can be present in juvenile scleroderma, focusing on ultrasonography, magnetic resonance imaging, and classic radiography. Ultrasound provides high-resolution images in real-time dynamic examination. With high-frequency transducers, it may provide a considerable input into the imaging of skin and musculoskeletal involvement. Several findings might be present when using B-mode or Doppler modalities such as thickening and hypervascularization of the cutis and subcutaneous tissue, synovitis and tenosynovitis, as well as small calcifications. Magnetic resonance imaging is also useful to evaluate inflammatory skin infiltration or skin atrophy, as well as deeply located structures, including fasciae, muscles and joints that might not be seen on ultrasonography. This modality is, however, expensive and time-consuming, and might require sedition in children. Classic radiology can show soft tissue calcifications, acroosteolysis, contractures, and subluxations. Computed tomography, which requires a high dose of radiation, is generally avoided in children, except in very specific cases.

Objectives: Cesarean section is a lifesaving procedure with short and long-term consequences. Growing rates of cesarean sections worldwide arise problems for subsequent birth. The aim of this study was to compare safety of vaginal birth after two cesarean sections with repeat third cesarean section to help healthcare providers and patients make well informed decisions about mode of subsequent delivery. Material and methods: This was a retrospective cohort study conducted in a tertiary reference hospital. Database of all deliveries (2010–2017) after two previous cesarean sections was created from electronic and paper medical records. Preterm deliveries, abnormal karyotype and neonates with congenital anomalies were excluded from the study. The final analysis included 412 cases for maternal outcome analysis and 406 cases for neonatal outcome analysis. Results: Trial of labor after two cesareans in comparison to repeat cesarean section increases the risk of hemorrhage (OR: 10.84) and unfavorable composite maternal outcome (OR: 2.58). Failed trial of labor increases this risk of hemorrhage (OR: 15.27) and unfavorable composite maternal outcome (OR: 4.59) even further. There were no significant differences in neonatal outcomes. 22 out of 35 trials of labor ended in successful delivery giving a success rate of 62.85%. 5 of 7 labor inductions ended in repeat cesarean section giving 28.6% success rate. There were no maternal deaths and emergency hysterectomies. Conclusions: Trial of labor, especially failed trial of labor, is associated with an increased risk of perinatal complications.

Modern Ti-based materials such as nanocrystalline α Ti and metastable β alloy Ti-29Nb-13Ta-4.6Zr (TNTZ) offers unique mechanical properties which are essential in case of dental implants. However, successful permanent implantation is governed also by material's functional properties such as corrosion behaviour in body fluids. Although both of this materials demonstrated high corrosion resistance in standard physiological solutions, the effect of simulated inflammatory conditions, which are more realistic following the implantation, is still unknown. Hence, in this work the influence of simulated inflammation on the corrosion response of nanocrystalline α Ti and metastable β TNTZ alloy was investigated and compared with the widely used microcrystalline α Ti. This study provides an insight how the presence of non-toxic β phase stabilizers and grain refinement to the nanoscale affect Ti corrosion behaviour in the simulated inflammatory conditions.

This study concerns a detailed cross-section microstructural analysis conducted by combining complementary methods such as FIB, SEM, EDS and STEM on different scales in order to elucidate the impact of direct laser interference lithography on the microstructure and surface chemistry of a Ti substrate after laser patterning. Special attention was paid to correlate the mechanical properties determined by the nanoindentation tests with the microstructure and phase composition analysed using GI-XRD. Direct laser interference lithography surface texturing results in the formation of a thin (1–1.5 μm), continuous layer with lath-like grains. The GI-XRD analysis showed no changes in phase composition, which is in agreement with our previous results. Furthermore, laser patterning led to an increase in the nano-hardness of the surface (from 2.8 GPa to 6.6 GPa) that is mainly related to the changes that took place in the microstructure. The results presented are important to an evaluation of laser-patterned surfaces in biomedical applications, as their ultimate use depends not only on topographical changes but also mechanical properties variations as well as microstructure evolution which affects its electrochemical properties.

Annealing deformed metals usually leads to reduced strength. In the case of nanocrystalline materials, the opposite effect was observed after low-temperature annealing. The annihilation of mobile dislocations and a relaxation of grain boundaries are probable reasons for the observed phenomenon. Dislocation density and grain boundaries character affect also on the corrosion resistance. Hence, in this work the effect of low-temperature annealing on both the hardness and corrosion resistance of nanotitanium was investigated. The results indicated that low-temperature annealing is a fast, simple and inexpensive way to further enhance nanotitanium's mechanical and corrosion properties, which are crucial for implantable materials.

In this work, the influence of bending an AA5457 alloy sheet and the resulting microstructural changes on its corrosion behavior was investigated. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to perform detailed microstructural analyses of the alloy in its original form and after bending. After immersion in naturally-aged NaCl under open-circuit conditions (0.5 M, adjusted to 3 by HCl), post-corrosion observations were made, and electrochemical polarization measurements were performed to investigate the corrosion mechanisms occurring on both surfaces. The results showed that the corrosion of AA5457 is a complex process that mainly involves trenching around coarse Si-rich particles, crystallographically-grown large pits, and the formation of multiple tiny pits around Si-rich nanoparticles. The experimental data showed that bending AA5457 changed the shape and distribution of Si-rich coarse particles, cumulated a higher dislocation density in the material, especially around Si-rich nanoparticles, and all of these factors caused that corrosion behavior of the AA5754 in the bending area was lowered.

Nanocrystalline titanium, mainly owing to its high corrosion resistance, mechanical strength to density ratio and biocompatibility, has a great application potential in dental implantology. However, fluoridated agents commonly used for oral hygiene could have a destructive influence on the titanium protective passive films and lead to the formation of local corrosion damages. In this work, the effect of nanostructuring on titanium corrosion resistance in the concentration of F− which is typical for toothpastes, was evaluated by different electrochemical and surface characterisation techniques. It was found that nanostructure influences beneficially on titanium corrosion resistance in fluoride solution. Furthermore, the lower increase in nanocrystalline titanium surface roughness in corrosion solutions indicates better stability of passive film formed on its surface.

This paper reports on the corrosion behavior of Titanium Grade 2 when subjected to non-contact laser functionalization. Direct Laser Interference Lithography (DLIL) was used to create periodic topography with two different surface patterns on pre-modified titanium. Corrosion resistance was measured in physiological saline at 37 °C. Electrochemical Impedance Spectroscopy data (EIS) and potentiodynamic polarization curves were correlated with the characteristics of the passive films through analysis of the topography, chemical composition, and thickness of oxides formed on the titanium after surface modifications. The corrosion tests showed that laser-textured surfaces have a beneficial impact on titanium corrosion resistance in a physiological saline solution 0.9% NaCl. Moreover, the passive layer on DLIL-modified samples is more stable and less susceptible to growth in the corrosive environment. The results highlight the local interaction of DLIL treatment of the titanium surface after it had been shot-peened and acid-etched. The improved corrosion resistance in DLIL samples derives mainly from changes in the surface topography, chemical composition, and thickness of oxide films obtained after laser processing.