Biomaterial

During the resorbable-polymer-boom of the 1970s and 1980s, polycaprolactone (PCL) was used in the biomaterials field and a number of drug-delivery devices. Its popularity was soon superseded by faster resorbable polymers which had fewer perceived disadvantages associated with long term degradation (up to 3-4 years) and intracellular resorption pathways; consequently, PCL was almost forgotten for most of two decades.

Polyethlene terephthalate films were surface-modified with polyethylene oxide (18 500 g/mol) using a solution technique described previously. These films were investigated for their resistance to bacterial adhesion. Three bacterial strains most commonly associated with implant infections, Staphylococcus epidermidis, Staphylococcus aureus and Pseudomonas aeruginosa, were cultured in tryptic soya broth, human plasma and human serum on the polymeric substrates. Significant reductions (between 70 and 95%) in adherent bacteria were observed on the polyethylene oxide-modified substrates compared to the untreated control polyethylene terephthalate.

Teflon is utilized in neurosurgery as well as in plastic, vascular and heart surgery. Although the effect of Teflon on different types of cells and tissues has been previously studied, we are not aware of any study in which the effect of Teflon was tested on cells of the central nervous system. We have therefore examined the tissue compatibility of spongy and fibrous Teflon by directly exposing the Teflon to dissociated cerebellar cells containing both glia and neurons in tissue culture. Daily examination of the growth of the cells adjacent to Teflon fibers using an inverted phase contrast microscope revealed that Teflon has little or no effect on the growth of these cells. When the cells are fixed after 7 days in culture and stained by the Jenner-Giemsa method, adhesion of both gila and neurons to the surface of the Teflon was seen. Attachment of neural cells to the Teflon was not extensive, as was shown by indirect immunofluorescence technique in connection with double-label staining with anti-GFAP as glia marker and anti-M6 as mouse neuron marker. Thus, these experiments show that Teflon is relatively inert when used as an implant in the central nervous system.

Fiber reinforced composites (FRCs) are more and more widely applied in dentistry to substitute for metallic restorations: periodontal splints, fixed partial dentures, endodontic posts, orthodontic appliances, and some other indirect restorations. In general in FRCs, the fiber reinforcement provides the composite structure with better biomechanical performance due to their superior properties in tension and flexure. Nowadays, the E-glass fiber is most frequently used because of its chemical resistance and relatively low cost. Growing interest is being paid to enhance its clinical performance. Moreover, various techniques are utilized to reinforce the adhesion between the fiber and the matrix. Oral conditions set special requirements and challenges for the clinical applications of FRCs. The biomechanical properties of dental materials are of high importance in dentistry, and given this, there is ongoing scientific interest to develop E-glass fiber reinforced composite systems. FRCs are generally biocompatible and their toxicity is not a concern.

Melt electrospinning is one aspect of electrospinning with relatively little published literature, although the technique avoids solvent accumulation and/or toxicity which is favoured in certain applications. In the study reported, we melt-electrospun blends of poly(ε-caprolactone) (PCL) and an amphiphilic diblock copolymer consisting of poly(ethylene glycol) and PCL segments (PEG-block-PCL). A custom-made electrospinning apparatus was built and various combinations of instrument parameters such as voltage and polymer feeding rate were investigated. Pure PEG-block-PCL copolymer melt electrospinning did not result in consistent and uniform fibres due to the low molecular weight, while blends of PCL and PEG-block-PCL, for some parameter combinations and certain weight ratios of the two components, were able to produce continuous fibres significantly thinner (average diameter of ca 2 µm) compared to pure PCL. The PCL fibres obtained had average diameters ranging from 6 to 33 µm and meshes were uniform for the lowest voltage employed while mesh uniformity decreased when the voltage was increased. This approach shows that PCL and blends of PEG-block-PCL and PCL can be readily processed by melt electrospinning to obtain fibrous meshes with varied average diameters and morphologies that are of interest for tissue engineering purposes.

Starting from the natural amino-acid L-tyrosine, a diphenolic monomeric molecule was developed using carbodiimide mediated solidphase synthesis techniques. This monomeric molecule was polymerized by reacting it in equimolar proportions with suitable dihalophosphates to yield novel biodegradable polyphosphates containing peptide linkages and phosphoester linkages alternating in the polymer backbone. The biodegradability of such a polymer is expected to arise from the hydrolytic degradability of the phosphoester linkages and the enzymatic degradability of the peptide linkages in the polymer backbone. Design of such a polymer is expected to make a significant contribution to biomaterials research, regarding drug delivery device and tissue engineering scaffold applications. The monomer was obtained by a novel solid phase carbodiimide-mediated amide coupling process. The subsequent polymers were obtained by solutionphase dehydrochlorination polycondensation reactions in the presence of a suitable acid acceptor. The synthesized polymers were characterized by 13 C NMR, 31 P NMR and FTIR for their chemical structure, by GPC for their molecular weight distribution, and by DSC and TGA for their thermal transition characteristics.

Brazil j o u r n a l o f d e n t i s t r y 3 9 ( 2 0 1 1 ) 2 5 5 -2 6 2 Microtensile bond strength Dentine adhesive a b s t r a c t Objective: This study tested the hypothesis that bond strength of total-and self-etching adhesive systems to dentine is not affected by the presence of remnants from either eugenol-containing (EC) or eugenol-free (EF) temporary cements after standardized cleaning procedures.

The concept of tissue and cell guidance is rapidly evolving as more information regarding the effect of the microenvironment on cellular function and tissue morphogenesis become available. These disclosures have lead to a tremendous advancement in the design of a new generation of multifunctional biomaterials able to mimic the molecular regulatory characteristics and the three-dimensional architecture of the native extracellular matrix. Micro-and nano-structured scaffolds able to sequester and deliver in a highly specific manner biomolecular moieties have already been proved to be effective in bone repairing, in guiding functional angiogenesis and in controlling stem cell differentiation. Although these platforms represent a first attempt to mimic the complex temporal and spatial microenvironment presented in vivo, an increased symbiosis of material engineering, drug delivery technology and cell and molecular biology may ultimately lead to biomaterials that encode the necessary signals to guide and control developmental process in tissue-and organ-specific differentiation and morphogenesis.

The delivery of the tetracycline and hydrocortisone drugs that have been incorporated into bioactive glasses was studied in this work. The potentiality of these systems in direct pulp capping is also discussed. A bioactive glass with a composition of (SiO 2 ) 0.80 (P 2 O 5 ) 0.04 (CaO) 0.16 , was prepared by sol-gel. Sols were prepared with the addition of approximately 2 wt% of tetracycline or hydrocortisone separately for the delivery studies. A third set of samples of bioglass sols containing 2 wt% of each drug were prepared with the same purpose. The amounts of drugs delivered were monitored by ultraviolet spectrophotometry in the tetracycline and hydrocortisone wavelengths. The drug release behavior was strongly dependent on the system. The glass-tetracycline samples showed a rapid drug release kinetics, while glasshydrocortisone samples show much slow release profiles. The different drug release behaviors have been explained by faster gel formation reaction between hydrocortisone and TEOS due to a stronger interaction between these reagents. On the samples with both drugs, the release was simultaneous and for each drug, the amounts delivered followed a profile similar to the samples with only this specific drug.

A novel infection-resistant biomaterial was created by applying the antibiotic Ciprofloxacin (Cipro) to a recently developed bifunctionalized polyethylene terephthalate ("polyester," Dacron) material using textile-dyeing technology. Dacron was modified via exposure to ethylenediamine (EDA) to create amine and carboxylic acid sites within the polymer backbone. Cipro was applied to the bifunctionalized Dacron construct under varied experimental conditions, with resulting antimicrobial activity determined via zone of inhibition. Dacron segments treated at a liquor ratio of 20:1, with 5% Cipro on weight of fabric (owf), at pH 8 for 4 h at 70°C followed by autoclaving showed antimicrobial activity for 78 days (length of study). Segments treated similarly but without autoclaving lost activity within 1 day. Dyeing time and temperature did not significantly affect antibiotic release/activity, but segments dyed at pHs higher or lower than 8 had less antimicrobial activity. The long-term infection resistance provided by this technique may answer major problems of infection from which implantable Dacron biomedical devices suffer.

The biology and physical properties of the uniquely human skin cream 'vernix caseosa' are discussed. This material coats the foetal skin surface during the last trimester of gestation and provides multiple beneficial functions for the foetus and newborn infant. Vernix has a complex structure similar to stratum corneum but lacks lipid lamellae and is more plastic due to the absence of desmosomal constraints. In utero, vernix is made in part by foetal sebaceous glands, interacts with pulmonary surfactant, detaches into the amniotic fluid, and is swallowed by the foetus. At the time of birth, vernix has a remarkably constant water content approximating 80%. Postnatally, vernix is simultaneously a cleanser, a moisturizer, an anti-infective, and an anti-oxidant. Vernix facilitates acid mantle development and supports normal bacterial colonization. Its hydrated cellular structure and unusual lipid composition provide a 'best' solution for the needs of the foetus and newbor...

Diffuse reflectance UV (DR-UV) spectroscopy was used for the first time to quantity the amount of creatinine adsorbed onto mordenite type zeolite from two different media: Phosphate Buffered Saline solution (D-PBS) and D-PBS solution containing albumin at a concentration corresponding to human serum conditions (50 g/L). The UV spectra of creatinine adsorbed onto mordenite zeolites was quantitatively treated using the Kubelka-Munk formalism. Quantification by diffuse reflectance UV spectroscopy after microporous solids extraction was linearly correlated with creatinine concentration whatever the medium. This study evidences that DR-UV spectroscopy may be an efficient method to directly quantify the amount of chosen molecules present in a liquid medium by pre-concentrating them on a specific solid adsorbent like in the solid phase extraction (SPE) procedure. The results on hand also prove that this is even possible in rather complex conditions. The method is simple, fast, and with a low detection threshold.

Nowadays, chemically synthesized proteins and peptides are attractive building blocks and have potential in many important applications as biomaterials. In this review, applications of biomaterials to thermotropic liquid crystals are discussed. The review covers the improvement of the performance of liquid crystal displays using liquid crystal physical gels consisting of a liquid crystal and amino acid-based gelators, and also new functionalization of liquid crystals. Moreover, the influence of DNA, which is one of the more attractive biomaterials, dispersed in thermotropic liquid crystals and its potential use in the liquid crystal industry is described. In addition, we found interesting results during electrooptical measurements of liquid crystals doped with DNA, and explain them from the point of view of biological applications. These recent approaches suggest that these biomaterials may be applicable in the electronic device industry and should be considered as an interesting material with their physical properties having the potential to create or refine an industrial product.

Distal radius fracture often presents a metaphyseal void which is more extended in elderly, osteoporotic patients. Bone graft and bone substitutes are reported to be beneficial in maintaining metaphyseal reduction. We performed a prospective study on 52 menopausal, osteoporotic women with unstable intra-articular distal radius fractures to compare the outcome of percutaneous pinning and immobilisation in a cast for 6 weeks with that using injectable calcium phosphate bone cement (Norian Skeletal Repair System, SRS) to supplement pin and screw fixation and immobilisation in a cast for 3 weeks. All patients were reviewed 2 years (range 21-29 months) after surgery. Patients treated with SRS had better functional outcome, restoration of movement and grip strength ( p<0.001). In this group there was 1 mm loss of radial length, 3 degrees loss of radial inclination and 7 degrees loss of palmar tilt. In the control group radial length decreased 3 mm, radial inclination decreased 11 degre...

Hyaluronic acid (HA) has been crosslinked in solution with glutaraldehyde (GTA), 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC), poly(ethylene glycol) diglycidylether (EX 810), and divinyl sulfone (DVS) to form hydrogels. Flory-Rehner calculations were used to determine molecular weight between crosslinks (M c), the crosslink density (V e), and mesh size (e) of crosslinked hydrogels after 24-h swelling in distilled water. Generally, lower molecular weight films gave rise to decreased molecular weights between crosslinks as well as increased effective crosslink densities and decreased mesh size. The effects of pH and salt concentration were evaluated. Use of lower molecular weight HA gave rise to decreased molecular weights between crosslinks as well as increased effective crosslink densities and decreased mesh size. Water diffusion coefficients were measured for DVS and GTA hydrogels and were found to be 1.4 3 10 210 and 1.8 3 10 210 m 2 s 21. Autocrosslinked and HA polyethyleneimine gels were also produced but had very limited stabilities compared with the covalently crosslinked materials.

Hydrogels are cross-linked polymeric networks, which have the ability to hold water within the spaces available among the polymeric chains. The hydrogels have been used extensively in various biomedical applications, e.g., drug delivery, cell carriers and/or entrapment, wound management and tissue engineering. Though far from extensive, this article has been devoted to study the common methods used for the characterization

The most commonly used bearing couple in prosthetic hip or knee joint replacements consists of a cobalt-chrome (CoCr) metal alloy articulating against ultrahigh-molecular-weight polyethylene. Ceramics have been used as an alternative to metal-on-polyethylene in joint replacement surgery of arthritic hips and knees since the 1970s. In prosthetic hip and knee bearings, ceramic surfaces offer a major benefit of drastically reduced wear rates and excellent long-term biocompatibility, which can increase the longevity of prosthetic hip and knee joints. This benefit is important clinically because hip and knee replacement has become a very common surgical procedure, particularly in the United States, and because these procedures are being increasingly performed in younger patients who place greater demands on the prosthetic bearings. However, ceramics are brittle and the risk of catastrophic bearing failure in vivo, while rare, is a major concern. Improvements in material quality, manufacturing methods, and implant design have resulted in a drastic reduction of the incidence of such failures, so that modern ceramic bearings are safe and reliable if used with components of proven design and durability. Future material improvements are actively being investigated to reduce the risk of ceramic-bearing failures even further. The purpose of this article is to review the structure, properties, applications, and limitations of the ceramics that have been used in orthopedic bearings, and to describe the new ceramic composite materials and surface treatments that will be available for joint replacement surgery in the near future. Feature D. Green-contributing editor *Member, American Ceramic Society.

Bond failures at the acrylic teeth and denture base resin interface are still a common clinical problem in prosthodontics. The effect of methyl methacrylate (MMA) monomer on the bond strength of three types of denture base resins (Acron MC, Lucitone 550 and QC-20) to two types of acrylic teeth (Biotone and Trilux) was evaluated. Twenty specimens were produced for each denture base resin/acrylic tooth combination and were randomly divided into control (acrylic teeth received no surface treatment) and experimental groups (MMA was applied to the surface of the acrylic teeth for 180 s) and were submitted to shear tests (1 mm/min). Data (MPa) were analyzed using three-way ANOVA/Student's test (a ¼ 0.05). MMA increased the bond strength of Lucitone denture base resins and decreased the bond strength of QC-20. No difference was detected for the bond strength of Acron MC base resin after treatment with MMA.

Objective: Resin infiltration is considered as a treatment option for initial caries lesions. As cavitated early lesions might require additional restorative intervention, a caries infiltrant might be also used for enamel conditioning prior to composite insertion. This study aimed to analyse the shear bond strength of a flowable composite to sound and demineralised enamel pretreated with a caries infiltrant, a conventional adhesive or a combination of both.

In the challenging quest for a solution to reduce the risk of implant-associated infections in bone substitution surgery, the use of silver ions is promising regarding its broad spectrum on planktonic, sessile as well as multiresistant bacteria. In view of controlling its delivery in situ at the desired dose, we investigated its encapsulation in carboxymethyl cellulose (CMC) microparticles by spray-drying and included the latter in the formulation of a self-setting calcium phosphate bone cement. We implemented an original step-by-step methodology starting from the in vitro study of the antibacterial properties and cytotoxicity of two silver salts of different solubility in aqueous medium and then in the cement to determine the range of silver loading able to confer anti-biofilm and non-cytotoxic properties to the biomaterial. A dose-dependent efficiency of silver was demonstrated on the main species involved in bone-implant infection (S. aureus and S. epidermidis). Loading silver in microspheres instead of loading it directly inside the cement permitted to avoid undesired silver-cement interactions during setting and led to a faster release of silver, i.e. to a higher dose released within the first days combining anti-biofilm activity and preserved cytocompatibility. In addition, a combined interest of the introduction of about 10% (w/w) silver-loaded CMC microspheres in the cement formulation was demonstrated leading to a fully injectable and highly porous (77%) cement, showing a compressive strength analogous to cancellous bone. This injectable silver-loaded biomimetic composite cement formulation constitutes a versatile bone substitute material with tunable drug delivery properties, able to fight against bone implant associated infection. STATEMENT OF SIGNIFICANCE: This study is based on two innovative scientific aspects regarding the literature: i) Choice of silver ions as antibacterial agent combined with their way of incorporation: Carboxymethylcellulose has never been tested into bone cement to control its drug loading and release properties. ii) Methodology to formulate an antibacterial and injectable bone cement: original and multidisciplinary step-by-step methodology to first define, through (micro)biological tests on two silver salts with different solubilities, the targeted range of silver dose to include in carboxymethylcellulose microspheres and, then optimization of silver-loaded microparticles processing to fulfil requirements (encapsulation efficiency and size). The obtained fully injectable composite controls the early delivery of active dose of silver (from 3h and over 2 weeks) able to fight against bone implant-associated infections.

With continued development and improvement of tissue engineering therapies for small articular lesions, increased attention is being focused on the challenge of engineering partial or whole synovial joints. Joint-scale constructs could have applications in the treatment of large areas of articular damage or in biological arthroplasty of severely degenerate joints. This review considers the roles of shape, loading and motion in synovial joint mechanobiology and their incorporation into the design, fabrication, and testing of engineered partial or whole joints. Incidence of degeneration, degree of impairment, and efficacy of current treatments are critical factors in choosing a target for joint bioengineering. The form and function of native joints may guide the design of engineered jointscale constructs with respect to size, shape, and maturity. Fabrication challenges for joint-scale engineering include controlling chemo-mechano-biological microenvironments to promote the development and growth of multiple tissues with integrated interfaces or lubricated surfaces into anatomical shapes, and joint-scale bioreactors which nurture and stimulate the tissue with loading and motion. Finally, evaluation of load-bearing and tribological properties can range from tissue to joint scale and can focus on biological structure at present or after adaptation.

We report a rapid method for the direct multicolor imaging of multiple subnuclear genetic sequences using novel quantum dot-based fluorescence in situ hybridization (FISH) probes (QD-FISH). Short DNA oligonucleotides were attached on QDs and used in a single hybridization/ detection step of target sites in situ. QD-FISH probes penetrate both intact interphase nuclei and metaphase chromosomes and showed good targeting of dense chromatin domains with minimal steric hindrances. We further demonstrated that QD's broad absorption spectra allowed different colored probes specific for distinct subnuclear genetic sequences to be simultaneously excited with a single excitation wavelength and imaged free of chromatic aberrations in a single exposure. Thus, these results demonstrate that QD-FISH probes are very effective in multicolor FISH applications. This work also documents new possibilities of using QD-FISH probes detection down to the single molecule level. NOTE ADDED IN PROOF As this manuscript went to press, Chan et al. published a similar QD-FISH method for the multiplex detection of mRNAs (24). Recent results by Xiao et al. suggest that pH effects on fluorescence of QD-detected hybridization signals could account for the absence of QD centromeric hybridization signals on human metaphase chromosomes in their FISH experiments (25).

as the differences in bone density make differences in bone to implant contact. b) Available remaining bone after extraction, which has a direct influence in choosing the width and the length of the implant, affecting the surface area and the bone to implant contact. c) Parafunctional habits, which increase time, magnitude, direction, and distribution of the forces affecting bone to implant contact. Forces and loading conditions applied on the implant Implant-related factors: a) Implant macro design (implant body, length and diameter, threads shape, pitch, lead, depth and width, and crest module), implant design is mainly responsible for 1-increase the surface area of the implant, 2-decrease the stress in addition to 3-distributing the forces on the bone and convert the stresses into favorable compressive stresses. b) Chemical composition and biomaterial of the implant and its relation to biocompatibility, enhancing healing, modulus of elasticity. c) Implant surface treatment and coatings (surface topography), responsible for increase the surface area of the BIC, decrease the stresses, enhance adhesion qualities to the bone-implant interface at initial healing.

Dental ceramics are generally considered to be chemically inert materials. However, characteristics of one dental ceramic are not necessarily present in another dental ceramic material. The aim of this study was to test the elution of sodium, potassium, magnesium, silicon and aluminium ions from feldspathic, alumina and glass–ceramics after 16 h of immersion in the acetic acid solution, according to ISO Standard 6872 method and to assess their potential toxicity. Elution was determined using the atomic absorption spectrophotometer (AAS) and UV–vis spectrophotometer. The highest leaching of the ions was shown for the feldspathic ceramic specimens and the lowest for the glass ceramic specimens. The release of the ions from the analyzed specimens did not correspond to their composition declared by the manufacturers. It can be concluded that the measured release of ions is not significant and correlates well with the data from the literature linked with glass corrosion, that is, silicate-based dental ceramics.

In the present work, natural coral from Brazilian reefs were studied according to their crystallography by X-ray diffraction and microstructure by Scanning Electron Microscopy (SEM/EDX). FTIR spectroscopy was also used to evaluate the chemical functionalities and major components present in the material. The SEM morphology results have shown a tri-dimensional coral structure with porous ranging from 50 to 200 µm. Aragonite was identified as the major crystalline phase through XRD analysis and FTIR spectroscopy. Strontium calcium carbonate, (Sr,Ca)CO 3 , was also identified by XRD analysis. After sintering at 900º/1h, the conversion from aragonite to CaO and calcite was observed. These results have endorsed the high potential application of natural coral materials as 3D scaffolds for biomedical application, because of calcium carbonate compounds can be converted to HA by hydrothermal and biomimetic coating processes.

Research in polymer nanofibers has undergone significant progress in the last decade. One of the main driving force for this progress is the increasing use of these polymer nanofibers for tissue engineering. Adequate porosity and surface area are widely recognized as important parameters in the design of scaffolds for tissue engineering and therefore measurement of porosity is very important. Previous methods such as mercury measurement, indirect method, the porosity measurement based on density of nanofibers do not measure the porosity of various surface layers. The goal of this study is measurement of porosity of various surface layers of scaffold. Image analysis was used for this purpose. SEM images of nanofibers mat were converted to binary images using different thresholds and porosity of scaffold was measured in various layers. On the basis of the results of our study, this method can be applied to porosity measurement of various surface layers of nanofibers mat. The results showed that porosity of various surface layers is related to the number of layers of nanofibers mat.

Membrane based medical therapies have increased considerably in recent years. At the same time, awareness of the side-effects caused by blood material incompatibility has grown. The necessity of mass production at low cost has also contributed to the formation of demands placed on any membrane used in medical applications today. These demands are application specific transport characteristics, high clearance, blood compatibility and a design enabling cost efficient ways of production. A theoretical approach relating membrane structure to transport properties suggests that the deciding factors are pore radius, porosity, tortuosity, diffusion coefficients, pore shape and protein adsorption potential. A hollow fiber structure, which fits these demands for hemodialysis, hemodialfiltration and hemofiltration, is a three-layer structure consisting of an inner blood facing skin layer, followed by a sponge structure and a macroporous finger structure. The influence of the membrane surface on protein adsorption, leading to a change in permeability, has also been investigated. Two concepts for limiting protein and cell interaction with artificial surfaces are introduced. Copolymerization and blending of hydrophobic and hydrophilic polymers have been successful approaches. To limit blood-membrane interactions, an optimized microdomain surface structure formed by hydrophilic patches in a hydrophobic matrix has evolved. In vitro test methods for measuring activation levels of coagulation, kallikrein-kinin pathways, cell stimulation and complement activation were necessary for the development of highly optimized artificial membranes made for hemodialysis, hemodiafiltration and hemofiltration. The Polyflux S membranes, consisting of the hydrophobic polymers polyamide and polyarylethersulfone as well as hydrophilic poylvinylpyrrolidone, with their integral three-layer microdomain structures performed well in all of the mentioned in vitro tests.

ÐIn testing for the cytotoxicity of medical devices, crucial parameters are the type of cells, the duration of the exposure, the physical form of the device and the method of evaluation. Using cell cultures the changes of cell functions induced by arti®cial materials may be evaluated. In screening tests the eect of biomaterials on functions common to all cell types is investigated through both continuous lines and primary cultures. In supplementary tests the eect of biomaterials on speci®c functions is studied, employing cells of the same type of those which will be in contact with the device in vivo. Osteoblasts, either from primary culture or an established line, are used to study the interaction with materials for bone implants. We evaluated whether dental cements aect the replication cycle of osteoblast-like cells MG63. The S phase was inhibited by the cements with a phenolic group, even though to a dierent extent. Mononuclear cell cultures are used to investigate the immune response, which is important in the host reaction to implant. We investigated whether the chromium ions released in a bio-logical¯uid may induce PBMC to produce cytokines involved in bone resorption. Chromium extract did not impair TNFa release signi®cantly, but inhibited IL-6 release signi®cantly in stimulated PBMC. Endothelial cell cultures are useful to the evaluation of materials for vascular grafts. We studied the inuence of some types of Dacron on endothelial functions. Collagen-coated Dacron decreased signi®cantly the production of 6-keto-prostaglandin F 1a. Knitted Dacron caused a signi®cant increase of tissue factor, a signi®cant reduction in PECAM-1 and a signi®cant increase in ELAM-1.

This article presents a comparative clinical study of reinforced zinc oxide eugenol (EBA) cement and amalgam used as retrograde root filling materials. Alli patients were followed for a minimum of 3 years after surgery. Clinical and radiographic evaluation was performed. Successful healing with complete bone regeneration was noted in 57% in the reinforced zinc oxide eugenol group compared with 52% in the amalgam group. Uncertain healing with a certain degree of bone regeneration was seen in 24% in the reinforced zinc oxide eugenol group compared with 19% in the amalgam group. Unsuccessful healing with failure of bone regeneration was seen in 20% in the reinforced zinc oxide eugenol group compared with 29% in the amalgam group. Statistical analysis failed to show any significant difference in healing between the two retrograde filling materials. The results of this study indicate that retrograde root filling with reinforced zinc oxide eugenol cement has a similar prognosis as with amalgam over a 3-

Bond failures at the acrylic teeth and denture base resin interface are still a common clinical problem in prosthodontics. The effect of methyl methacrylate (MMA) monomer on the bond strength of three types of denture base resins (Acron MC, Lucitone 550 and QC-20) to two types of acrylic teeth (Biotone and Trilux) was evaluated. Twenty specimens were produced for each denture base resin/acrylic tooth combination and were randomly divided into control (acrylic teeth received no surface treatment) and experimental groups (MMA was applied to the surface of the acrylic teeth for 180 s) and were submitted to shear tests (1 mm/min). Data (MPa) were analyzed using three-way ANOVA/Student's test (a ¼ 0.05). MMA increased the bond strength of Lucitone denture base resins and decreased the bond strength of QC-20. No difference was detected for the bond strength of Acron MC base resin after treatment with MMA.

In this study, three-dimensional silk fibroin/chitosan (SF/CTS) composite sponges were successfully prepared with an interconnected porous structure and proper mechanical properties. Silk fibroin and chitosan have the potential to mimic a natural extra-cellular matrix (ECM). For the sponge preparation, silk fibroin from the Bombyx mori silkworm and chitosan were used, in different proportions, as composites. Sponges were prepared by means of freezing and lyophylization of corresponding composite solutions. The properties of composite sponges, such as the microstructure as well as the chemical and physical properties were studied. In the present investigation, silk fibroin, chitosan and their mixtures were characterized by attenuated total reflection Fourier transform infra-red spectroscopy (ATR-FTIR), swelling properties, thermogravimetric analysis and scanning electron microscopy (SEM). The ATR-FTIR analysis indicated a shift of band corresponding to C_O, C\N, C\O\C. Moreover, NH groups of SF and C_O and NH 2 groups of chitosan might have participated in a specific intermolecular interaction among themselves. Thermogravimetric results suggested a higher temperature of decomposition for SF/CTS sponges than sponges made of pure silk fibroin or chitosan. Scanning electron microscopy observations showed the sponges of SF/CTS with pore size from 20 to 150 μm, which is appropriate for cell growth. Biocompatibility of sponges was confirmed by in vitro test. SF/CTS sponges have sufficient mechanical integrity to resist handling during implantation and in vivo loading. Both the compressive modulus and compressive strength for the sponge decrease with the increase of silk fibroin content in the sponge. Sponges made of silk fibroin/chitosan mixtures can be interesting materials for tissue engineering as scaffold for temporary supporting the formation of new tissue and organs.

This work studied the feasibility of producing a dual-phase aluminium bronze alloy and the use of selected treatments to manipulate the mechanical properties of the produced alloy using local techniques, as a potential replacement for conventional structural materials, particularly steels. Sand casting was used and was found to be effective based on its advantages of low cost, ease of use and flexibility in the production of a dual-phase aluminium bronze alloy with pre-selected composition of 11% Al content. Cold deformation of 10 and 20% degrees and selected heat treatments were used on the cast alloy to influence its mechanical properties. The selected heat treatments are solution heat treatment, normalising, and ageing. The results showed that normalising gave the optimum mix of tested mechanical properties with ultimate tensile strength in the range of 325 MPa, elongation of around 60% and Rockwell hardness values of 46.5 -63.7 HRc, making this alloy suitable as alternatives to steel in low/medium strength structural applications.

The purpose of this work was to develop a textile finish based on radical UV-curing of chitosan on cotton and silk to confer antimicrobial properties. Fabrics were impregnated with a solution of 2% w chitosan in aqueous acetic acid (2% v/v) added of 2-hydroxy-2-methylphenylpropane-1-one (2% w/w with respect to chitosan) as photoinitiator and cured at room temperature by exposure to UV lamp for 60 s on both the sides. The antimicrobial activity of finished fabrics was tested according to ASTM standard test performed with Escherichia coli. Obtained results showed a strong antimicrobial activity conferred by the treatment, homogeneous on fabric surface, without affecting the hand properties of fabrics due to the low chitosan weight on (about 2%). The treatment durability to domestic laundering was tested after 5 cycles using either anionic or nonionic detergents. The antimicrobial activity resulted completely maintained after washing with a nonionic surfactant, while with anionic detergents the treatment durability was better for samples prepared with a deeper penetration of chitosan inside the fibers. The fabrics were characterized by dyeing tests, SEM and FTIR-ATR analyzes.

The effect of fiber lignin content on biocomposite properties was investigated. Coconut fiber was treated with 0.7% sodium chlorite to selectively decrease amounts of lignin. The fiber lignin content was then reduced from 42 to 21 wt.%. The composition and mechanical properties of the individual modified fibers were characterized. Gluten-based materials reinforced with modified fibers were prepared by compression molding. Then, the mechanical properties, water sensibility, matrix glass transition and infrared spectra of biocomposites prepared with fibers containing various amounts of lignin were evaluated. This study showed that the addition of coconut coir fiber significantly improved properties of wheat gluten biomaterials. In addition, the variation of lignin content in the fibers, in the investigated range, had no significant effect neither on matrix deplasticization nor fiber/matrix adhesion, suggesting that a partial lignin removal is not an efficient way to improve the properties of natural fiber/plasticized protein biocomposites.

Poly Methyl Methacrylate were widely accepted material in dental and medical field due to the excellent biocompatibility and easy fabrication, however exhibit inferior mechanical properties. Therefore, the present study conducted to determine the flexural properties of PMMA based material by reinforcing PMMA with two different natural fibers (bamboo & siwak fibers). Discontinuous random fibers used in three lengths (2, 6 & 12 mm) and three weight percentage (3, 6 & 9 wt. %) of the both types of fibers. Results indicated that Flexural modulus, flexural strength and max.shear stress increase with increasing weight fraction and fiber length of fibers (bamboo & siwak) and reach the maximum amount at addition of weight fraction of (9 wt.%) and (12mm) length of fibers. The highest value of flexural modulus, flexural strength and max.shear stress were (10.09GPa), (112MPa), (6MPa) respectively, for composite specimens with bamboo fibers, while for composite specimen with siwak fibers (9.71GPa),(101MPa),(4.44MPa) at the optimum condition of (9wt.%) and (12mm) length. All composite specimens reinforced with bamboo fibers showed the highest flexural strength and flexural modulus among the composite specimen reinforced by siwak fibers.

The cosmetic market for hyaluronic acid (HA)-based dermal fillers is in continuous and rapid growth and, simultaneously, the development of more effective and safer products is strongly intensifying. In order to highlight the differences among the currently available fillers, in terms of their physical characteristics and on the relation of such properties with product effectiveness, an in vitro evaluation of eight marketed HA-based gels was performed.

The role of artificial skin substitutes in burn surgery and the treatment of chronic wounds is constantly evolving. New products are regularly being produced and approved for clinical use. Studies on existing products clarify their efficacy and effectiveness in different clinical scenarios. This review is aimed at busy clinicians in order to bring them up to date with the latest developments in the field of artificial skin substitutes. It examines the components, structure, performance and comparative costs of the main commercial skin substitutes, and reviews briefly technologies under development that have not yet become widely available. 9 2002 The British Association of Plastic Surgeons

Fiber reinforced composites (FRCs) are more and more widely applied in dentistry to substitute for metallic restorations: periodontal splints, fixed partial dentures, endodontic posts, orthodontic appliances, and some other indirect restorations. In general in FRCs, the fiber reinforcement provides the composite structure with better biomechanical performance due to their superior properties in tension and flexure. Nowadays, the E-glass fiber is most frequently used because of its chemical resistance and relatively low cost. Growing interest is being paid to enhance its clinical performance. Moreover, various techniques are utilized to reinforce the adhesion between the fiber and the matrix. Oral conditions set special requirements and challenges for the clinical applications of FRCs. The biomechanical properties of dental materials are of high importance in dentistry, and given this, there is on-going scientific interest to develop E-glass fiber reinforced composite systems. FRCs are generally biocompatible and their toxicity is not a concern.

The term "nanoleakage" has been introduced to explain a penetration pathway within hybrid layers of the dentin-composite junction in the absence of gap formation. This phenomenon is argued in the literature to be a risk factor for the quality of the dentin bonding. NaOCl is a well-known agent used to remove collagen layers that are exposed after acid etching. The purpose of this study was to determine the influence of an NaOCl treatment of dentin to the formation of nanoleakage. Class V cavities were prepared in 40 human molars with the cervical margins located in dentin. After etching with phosphoric acid, 20 samples were treated with 10% NaOCl for 60 s, and 20 samples were used as control. Composite restorations were placed using two different bonding systems. The specimen were exposed in silver nitrate solution and then in developer. After embedding, the teeth were sectioned, dried, coated with gold, and analyzed by SEM. For all the specimen in the control group, backscatter images indicated a silver penetration within the hybrid layer. There was no penetration of silver detectable in the teeth that were treated with NaOCl. We conclude that the removal of the collagen layer by using NaOCl avoids the formation of nanoleakages with the materials tested.

The turtle shell is an amazing structure optimized through the long-term evolution by nature. This paper reports the mechanical response of the shell (Red-ear turtle) to static and dynamic loads, respectively. It is found that the turtle shell under a compressive load yields the maximum vertical displacement at the rear end, but the vertical displacement at the front end is only half of that at the rear end. The maximum horizontal displacement of the shell also occurs at the rear end. It is believed that such a deformation pattern is helpful for protecting the turtle's internal organs and its head. The principal stress directions in the inside surface of the shell under a compressive load are almost the same as those of the biofiber distribution in the inside surface, which results in the strong bending resistance of the turtle shell.