The reactivity of aluminum and several other divalent and trivalent metallic cations toward chromatin from rat brain and liver has been investigated. Two criteria are used to determine the relative reactivity of these cations toward chromatin. The first involves the ability of the ions to compact the chromatin fibers to the point where chromatin precipitates. The second criterion measures the ability of cations to interfere with the accessibility of exogenous structural probes (nucleases) to chromatin. Of the divalent cations tested, nickel, cobalt, zinc, cadmium, and mercury were the most reactive toward chromatin, on the basis of their ability to induce precipitation of chromatin in the micromolar concentration range. The divalent cations magnesium, calcium, copper, strontium, and barium were much less effective, although all cations precipitate chromatin if their concentration is increased. Of the trivalent cations tested, aluminum, indium, and gallium were very effective precipitants, whereas iron and scandium were without effect at the concentrations tested. Of all the cations tested, aluminum was the most reactive. Aluminum's ability to alter the structure of chromatin was investigated further by testing its ability to interfere with nuclease accessibility. This test confirmed that aluminum does induce considerable changes in chromatin structure at micromolar concentrations. Furthermore, chromatin from cortical areas of the brain was much more sensitive to aluminum than chromatin from liver. These results are discussed in light of the known toxicity of these cations, with particular emphasis on the possible role of aluminum in Alzheimer's disease.

To develop a novel biomedical titanium alloy with a changeable Young's modulus via deformation-induced ω phase transformation for the spinal rods in spinal fixation devices, a series of metastable β type binary Ti-(15-18)Mo alloys were prepared. In this study, the microstructures, Young's moduli and tensile properties of the alloys were systemically examined to investigate the effects of deformation-induced ω phase transformation on their mechanical properties. The springback of the optimal alloy was also examined. Ti-(15-18)Mo alloys subjected to solution treatment comprise a β phase and a small amount of athermal ω phase, and they have low Young's moduli. All the alloys investigated in this study show an increase in the Young's modulus owing to deformation-induced ω phase transformation during cold rolling. The deformation-induced ω phase transformation is accompanied with {332}(β) mechanical twinning. This resulted in the maintenance of acceptable ductility with relatively high strength. Among the examined alloys, the Ti-17Mo alloy shows the lowest Young's modulus and the largest increase in the Young's modulus. This alloy exhibits small springback and could be easily bent to the required shape during operation. Thus, Ti-17Mo alloy is considered to be a potential candidate for the spinal rods in spinal fixation devices.Copyright © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Current trends in clinical dental implant therapy include use of endosseous dental implant surfaces embellished with nanoscale topographies. The goal of this review is to consider the role of nanoscale topographic modification of titanium substrates for the purpose of improving osseointegration. Nanotechnology offers engineers and biologists new ways of interacting with relevant biological processes. Moreover, nanotechnology has provided means of understanding and achieving cell specific functions. The various techniques that can impart nanoscale topographic features to titanium endosseous implants are described. Existing data supporting the role of nanotopography suggest that critical steps in osseointegration can be modulated by nanoscale modification of the implant surface. Important distinctions between nanoscale and micron-scale modification of the implant surface are presently considered. The advantages and disadvantages of nanoscale modification of the dental implant surface are discussed. Finally, available data concerning the current dental implant surfaces that utilize nanotopography in clinical dentistry are described. Nanoscale modification of titanium endosseous implant surfaces can alter cellular and tissue responses that may benefit osseointegration and dental implant therapy.

Titanium (Ti) osseointegration is critical for the success of dental and orthopedic implants. Previous studies have shown that surface roughness at the micro- and submicro-scales promotes osseointegration by enhancing osteoblast differentiation and local factor production. Only relatively recently have the effects of nanoscale roughness on cell response been considered. The aim of the present study was to develop a simple and scalable surface modification treatment that introduces nanoscale features to the surfaces of Ti substrates without greatly affecting other surface features, and to determine the effects of such superimposed nano-features on the differentiation and local factor production of osteoblasts. A simple oxidation treatment was developed for generating controlled nanoscale topographies on Ti surfaces, while retaining the starting micro-/submicro-scale roughness. Such nano-modified surfaces also possessed similar elemental compositions, and exhibited similar contact angles, as the original surfaces, but possessed a different surface crystal structure. MG63 cells were seeded on machined (PT), nano-modified PT (NMPT), sandblasted/acid-etched (SLA), and nano-modified SLA (NMSLA) Ti disks. The results suggested that the introduction of such nanoscale structures in combination with micro-/submicro-scale roughness improves osteoblast differentiation and local factor production, which, in turn, indicates the potential for improved implant osseointegration in vivo.Copyright © 2011 Elsevier Ltd. All rights reserved.

The bone-bonding ability of a material is often evaluated by examining the ability of apatite to form on its surface in a simulated body fluid (SBF) with ion concentrations nearly equal to those of human blood plasma. However, the validity of this method for evaluating bone-bonding ability has not been assessed systematically. Here, the history of SBF, correlation of the ability of apatite to form on various materials in SBF with their in vivo bone bioactivities, and some examples of the development of novel bioactive materials based on apatite formation in SBF are reviewed. It was concluded that examination of apatite formation on a material in SBF is useful for predicting the in vivo bone bioactivity of a material, and the number of animals used in and the duration of animal experiments can be reduced remarkably by using this method.

To compare early bone healing around different experimental titanium implant surfaces and to evaluate the role of a calcium phosphate-coated implant surface because it relates to bone-implant contact (BIC).An experimental hydroxyapatite (HA) grit-blasted and dual acid-etched titanium surface (BAE-1) was compared to an experimental HA grit-blasted and dual acid-etched surface treated with nanometer-scale crystals of HA (BAE-2). Both experimental implant surfaces were implanted onto the tibias of 4 New Zealand white rabbits. The animals were killed at 1,6, 21, and 90 days after the implant surgery. Descriptive histology was performed at the healing responses of both implant surfaces. Quantitative morphology assessment provided measurements of BIC, number of bone multicellular units (BMUs), average penetration of BMUs, and maximum penetration of BMUs that were manually made using imaging computer software.The overall BIC for the BAE-2 implant was higher than that for the BAE-1 implant at 21 days of healing. However, there was no significant difference at 90 days of healing.It is concluded from this animal pilot study that the bioactive BAE-2 implant surface provided a better BIC with healthy bone remodeling at 21 days of healing.

Dental implants are usually made from commercially pure titanium or titanium alloys. The aim of this investigation was to determine the influence of surface treatments of commercially pure titanium samples on in vitro bioactivity.Commercially pure (cp) titanium (Ti) sheets were submitted to three different surface treatments, including, for all samples, etching with an HCl/H(2)SO(4) solution. Part of each etched sample was further submitted either to anodic oxidation by using an H(3)PO(4) solution or to thermal oxidation. Treated and non-treated samples were analyzed by using scanning electron microscopy (SEM), profilometry and photoelectron X-ray spectroscopy (XPS). The in vitro assessment was carried out through the immersion of samples in simulated body fluid (SBF). In vitro testing was carried out by SEM and by the determination of calcium (Ca) content in solution by atomic absorption spectrometry (AAS). The non-treated titanium samples were used as the control group.This study has shown that, after up to 7-day exposure, a calcium phosphate layer precipitated only on samples submitted to at least one of the three treatments used. This result, based on SEM images, is in good agreement with Ca content and XPS analysis, in which remarkable effects of surface modifications on Ti samples are highlighted.These results suggest that suitable surface treatments, such as employed here, may improve in vitro titanium bioactivity in a SBF solution at 37 degrees C. This behavior suggests a possibility of a further favorable in vivo response.

The osseointegration rate of titanium dental implants is related to their composition and surface roughness. Rough-surfaced implants favor both bone anchoring and biomechanical stability. Osteoconductive calcium phosphate coatings promote bone healing and apposition, leading to the rapid biological fixation of implants. The different methods used for increasing surface roughness or applying osteoconductive coatings to titanium dental implants are reviewed. Surface treatments, such as titanium plasma-spraying, grit-blasting, acid-etching, anodization or calcium phosphate coatings, and their corresponding surface morphologies and properties are described. Most of these surfaces are commercially available and have proven clinical efficacy (>95% over 5 years). The precise role of surface chemistry and topography on the early events in dental implant osseointegration remain poorly understood. In addition, comparative clinical studies with different implant surfaces are rarely performed. The future of dental implantology should aim to develop surfaces with controlled and standardized topography or chemistry. This approach will be the only way to understand the interactions between proteins, cells and tissues, and implant surfaces. The local release of bone stimulating or resorptive drugs in the peri-implant region may also respond to difficult clinical situations with poor bone quality and quantity. These therapeutic strategies should ultimately enhance the osseointegration process of dental implants for their immediate loading and long-term success.

We report on the in vivo histological and mechanical performance of titanium dental implants with a new surface treatment (2Step) consisting of an initial grit-blasting process to produce a micro-rough surface, followed by a combined chemical and thermal treatment that produces a potentially bioactive surface, i.e., that can form an apatitic layer when exposed to biomimetic conditions in vitro. Our aim was to assess the short- and mid-term bone regenerative potential and mechanical retention of 2Step implants in mandible and maxilla of minipigs and compare them with micro-rough grit-blasted, micro-rough acid-etched, and smooth as-machined titanium implants. The percent of bone-to-implant contact after 2, 4, 6, and 10 weeks of implantation as well as the mechanical retention after 4, and 6 weeks of implantation were evaluated with histometric and pull-out tests, respectively, as a measure of the osseointegration of the implants. We also aimed to assess the bioactive nature of 2Step surfaces in vivo. Our results demonstrated that the 2Step treatment produced micro-rough and bioactive implants that accelerated bone tissue regeneration and increased mechanical retention in the bone bed at short periods of implantation in comparison with all other implants tested. This was mostly attributed to the ability of 2Step implants to form in vivo a layer of apatitic mineral that coated the implant and could rapidly stimulate (a) bone nucleation directly on the implant surface, and (b) bone growing from the implant surface. We also proved that roughness values of Ra≈4.5 μm favoured osseointegration of dental implants at short- and mid-term healing periods, as grit-blasted implants and 2Step implants had higher retention values than as machined and acid-etched implants. The surface quality resulting from the 2Step treatment applied on cpTi provided dental implants with a unique combination of rapid bone regeneration and high mechanical retention.Copyright © 2011 Elsevier Ltd. All rights reserved.

Polystyrene latex samples have been synthesised from an oil-in-water (o/w) emulsion of the monomer using ultrasonic irradiation as the initiation source. No added chemical initiators were used in any of the reactions. The free radicals formed from the cavitation process under the action of the ultrasound are sufficient to initiate the polymerisation. In the current study, the effects of varying the input intensity of the ultrasound were investigated. A marked increase in the monomer conversion rate as a function of time was seen as the power was increased. Despite this increase in conversion rate, the increasing intensity did not affect the resultant latex particle sizes. In all cases, the particle diameters at the conclusion of a polymerisation were seen to be in the range of 40 to 50 nm. The effects of changing the concentration of surfactant in the polymerisation medium and of changing the temperature were also probed. Increases in both were seen to lead to an increased rate of conversion at a fixed input intensity. Again, the particle diameters were invariant as a function of changing conditions. The small particle sizes and high conversion rates are thought to be due to a continuous nucleation process that is caused by the scavenging of free radicals throughout the polymerisation by freshly formed small oil droplets.

Surface-textured calcium phosphate coatings at four different length scales were synthesized on titanium-based alloys using a pulsed Nd:YAG laser system by a direct melting technique. The textures were obtained by varying the laser spot overlap with a change in laser traverse speed. Surface roughness measurements of the textured coatings carried out using a white light interferometer indicated a decrease in roughness with increasing laser scan speed. Wettability of the coated samples measured using a static sessile drop technique demonstrated an increased hydrophilicity with increasing laser scan speed. The influence of such textures and the associated surface roughness on the precipitation kinetics of hydroxyapatite (HA) during immersion in simulated body fluid (SBF) was the prime focus of the present paper. The mineralized samples obtained after immersion in SBF were characterized using X-ray diffraction, energy-dispersive spectroscopy and scanning electron microscopy to understand the kinetics of HA precipitation. The results thereafter confirmed that the precipitation kinetics of HA was strongly modulated by the varying surface roughness.

Among the host of substratum properties that affect animal cell behavior, surface morphology has received relatively little attention. The earliest effect of surface morphology on animal cells was discovered almost a century ago when it was found that cells became oriented in response to the underlying topography. This phenomenon is now commonly known as contact guidance. From then until very recently, little progress has been made in understanding the role of surface morphology on cell behavior, primarily due to a lack of defined surfaces with uniform morphologies. This problem has been solved recently with the development of photolithographic techniques to prepare substrata with well defined and uniform surface morphologies. Availability of such surfaces has facilitated systematic in vitro experiments to study influence of surface morphology on diverse cell physiological aspects such as adhesion, growth, and function. For example, these studies have shown that surfaces with uniform multiples parallel grooves can enhance cell adhesion by confining cells in grooves and by mechanically interlocking them. Several independent studies have demonstrated that cell shape is a major determinant of cell growth and function. Because surface morphology has been shown to modulate the extent of cell spreading and cell shape, its effects on cell growth and function appear to be mediated via this biological coupling between cell shape and function. New evidence in the cell biology literature is emerging to suggest that surface morphology could affect other cell behavioral properties such as post-translational modifications. Further elucidation of such effects will enable better designs for implant and cell culture substrata.

The aim of the present study was to examine bone response to micro-rough titanium implants. Forty coin-shaped implants were divided into eight groups according to their surface roughness. The first group had electropolished surfaces. The surfaces of implant groups 2-8 were blasted with TiO2 particles with incremental grain sizes ranging from 7.5-12.5 to 270-330 microns. Five implants from each group were placed into the cortical bone of the proximal tibia in New Zealand Black rabbits. To avoid bone overgrowth during the retention phase the implants were fitted into tight polytetrafluoroethylene (PTFE) caps leaving only the flat test surface exposed to bone. The healing period was set to 10 weeks, and implants with attached bone were evaluated using a tensile testing machine. In groups 1-7 a significant correlation between the micro-roughness of the implant surfaces and retention strength was observed. Maximum bone bonding was observed with implants blasted with 180-220 microns grain size (group 7). Blasting with larger TiO2 particles appeared to decrease the effect. The findings suggest that the best grain size of TiO2 particles for optimising retention of titanium implants in cortical bone should be in the 180-220 microns range.