bluuebunny/crossref_metadata_2025 huggingface dataset:
Optical methods for the nondestructive evaluation of collagen morphology in bioprosthetic heart valves
Authors: Hilbert Stephen L. , Ferrans Victor J. , Swanson W. Milton
Published: December 2004

The aim of the present study was to assess the suitability of nondestructive optical methods as a means of evaluating collagen morphology in bioprosthetic heart valve leaflets. The results of this study demonstrate that transmitted polarized light and incident polarized light optics facilitate the imaging of the inherent birefringence of valvular collagen fibers. Polarized light optics readily document the different patterns of collagen orientation and configuration in porcine aortic valvular (PAV) and bovine pericardial valvular (BPV) bioprostheses. Incident polarized light optics also provide information on leaflet surface morphology. Verification that the birefringence observed by polarized light optics represents leaflet collagen was provided by conventional histologic and transmission electron microscopic methods. Quantitative determinations of the spacing of collagen bundle waves gave similar values in intact and in sectioned BPV leaflets. Potential applications of polarized light optics in the assessment of bioprosthetic valve collagen are as follows: (1) the selection of the desired orientation of collagen bundles within pericardium intended to be configured into bioprosthetic leaflets; (2) evaluation of the effects of mechanical stresses and leaflet motion on collagen morphology in bioprosthetic valve leaflets; and (3) initial screening of leaflet specimens and selection of the desired collagen orientation for embedding and sectioning of samples for conventional morphologic studies.
Long‐term evaluation of five biomaterials for angioplastic enlargement of the pulmonary artery in a young dog model
Authors: Planche C. L. , Fichelle J. M. , Paul J. , Lethias C. L. , Elroy R. , Weiss M.
Published: December 2004

In 45 young dogs an enlargement angioplasty of the left pulmonary artery was performed using patches made from one of three autologous materials (jugular vein, unmodified pericardium, and glycerolized pericardium) or from two heterologous materials (lyophilized human dura mater and modified bovine carotid artery). Catheterization and angiographic studies performed 5 to 6 months after the operation showed that all patched vessels had remained patent, except in three dogs which had received heterologous implants. The animals were killed 5‐24 months after operation (mean weight increase: 84%), and the implants were studied by optical microscopy and morphometry, scanning and transmission electron microscopy, and indirect immunofluorescence with antidog Factor VIII rabbit antiserum. The two heterologous tissues exhibited limited biocompatibility, as estimated from 10 criteria obtained at histologic studies. Conversely, all three autologous biomaterials were characterized by infiltration of noninflammatory cells, near‐complete endothelialization, and neosynthesis of structural proteins; infectious foci were very rare or absent. These results suggest that autologous tissues, although deendothelialized at the time of implantation, constitute the most suitable material for patch angioplasty, as far as endothelial triggering, cellularity and resistance to infection are concerned.
Soft‐tissue response to total hip surface replacement
Authors: Skinner Harry B. , Mebey Monique F.
Published: December 2004

Tissue reaction to prosthesis wear debris and its relationship to prosthetic loosening was investigated. Eighteen dogs underwent hip surface replacement; 6 animals accounted for 6 control and 6 carbon hips, and 13 experimental animals accounted for 13 implanted carbon and 13 cobaltchromium‐molybdenum (CoCrMo) prostheses. Both kinds of prostheses articulated against a high‐density polyethylene acetabular component. One year after implantation, tissue response to the prostheses was evaluated according to a semiquantitative method, and a total tissue score indicating the degree of tissue response was obtained. The total tissue score was then compared with the normalized final vertical ground reaction force (GRF) for each hip in the animals with bilateral hip replacements. Compared with the controls, significantly greater tissue response was seen in both kinds of prosthetic hips (p = .001). No statistically significant difference in the tissue response of the two types of hip prostheses was noted, although the tissue response score of the CoCrMo demonstrated a trend toward more severe reaction than the carbon. No statistical difference in tissue reaction was noted for loosened components as compared with tightly fixed components. Amount of wear debris was the best predictor of component loosening. Gait analysis demonstrated a statistically significant negative correlation between GRF and total tissue score (p = .036), and between GRF and wear debris score (p = .034). The results of this study suggest that GRF may predict the amount of wear debris in the tissues surrounding a total hip surface arthroplasty, and that severity of pain is related to the degree of tissue response.
UV‐radiation aging test on composite materials for dental restorations
Authors: Gatti A. M.
Published: December 2004

Seven composite materials for dental restorations were examined in order to investigate their color stability. Five of these materials are available for anterior and two for posterior teeth. the change in color was achieved by an accelerated aging test with ultraviolet rays and evaluated, for each material, with the measurement of reflectance. Such measurement was obtained by means of a video display computer working as a computerized photometer. The results show two different types of behavior: some materials turn slightly to yellow, while others bleach. The test was completed with a scanning electron microscope morphologic examination of the surfaces.
Adsorption of fibronectin derived from serum and from human endothelial cells onto tissue culture polystyrene
Authors: van Wachem P. B. , Mallens B. W. L. , Dekker A. , Beugeling T. , Feijen J. , Bantjes A. , Detmers J. P. , van Aken W. G.
Published: December 2004

Human endothelial cells (HEC) suspended in a culture medium containing 20% human serum (CMS) adhere and spread on(to) moderately wettable polymers, such as tissue culture polystyrene (TCPS). We have previously shown that serum derived‐fibronectin, which is a cell adhesion promoting protein, has a high affinity for TCPS, but that the amount of fibronectin which adsorbed from CMS was relatively small. In this study we investigated whether fibronectin derived from HEC contributes to the adhesion and spreading of the cells on(to) TCPS. Therefore, HEC were seeded in the presence of fibronectin‐depleted CMS. The amount of fibronectin detected on TCPS increased with both cell seeding density and incubation time. Although initial HEC adhesion is delayed on TCPS which had been precoated with albumin (Alb), high density lipoprotein (HDL) or immunoglobulin G(IgG), maximal numbers of adhering and spreading HEC were found on these surfaces 6 h after seeding of HEC. Fibronectin was detected on these surfaces, but an exchange of preadsorbed Alb, HDL, or IgG for fibronectin could not be demonstrated. We conclude that HEC deposit fibronectin onto TCPS, irrespective of the presence of a preadsorbed layer of proteins which delay cell adhesion.
The effect of post‐sintering heat treatments on the fatigue properties of porous coated Ti‐6Al‐4V Alloy
Authors: Cook Stephen D. , Thongpreda Nisra , Anderson Ronald C. , Haddad Ray J.
Published: December 2004

Porous coated Ti‐6Al‐4V alloy implant systems provide a biocompatible interface between implant and bone, resulting in firm fixation and potential long‐term retention via bony ingrowth. In order to achieve an acceptable porous coating structure, the sintering protocol for Ti‐6Al‐4V alloy systems often requires that the material be heat treated above the beta transus. This transforms the as‐received equiaxed microstructure, recommended for surgical implants, to a lamellar alpha‐beta distribution, which has been shown to have the worst fatigue properties of the most common structures attainable in Ti‐6Al‐4V alloy. However, post‐sintering heat treatments may be used to improve these properties by producing microstructures more resistant to crack initiation and propagation. This study investigated the influence of microstructural variations on the fatigue properties of porous coated Ti‐6Al‐4V alloy material. Nonporous coated and porous coated Ti‐6Al‐4V alloy fatigue specimens were subjected to a standard sintering heat treatment to produce a lamellar microstructure. In addition, two post‐sintering heat treatments were used to produce coarse and fine acicular microstructures. Rotating beam (reversed bending) fatigue testing was performed and the endurance limits determined for the noncoated and porous coated microstructures. The values determined were 668 MPa (noncoated asreceived equiaxed), 394 MPa (noncoated lamellar), 488 MPa (non‐coated coarse acicular), 494 MPa (noncoated fine acicular), 140 MPa (porous coated lamellar), 161 MPa (porous coated coarse acicular), and 162 MPa (porous coated fine acicular). The noncoated coarse and fine acicular specimens displayed an approximate 25% increase over the noncoated lamellar specimens. The porous coated coarse and fine acicular specimens showed an approximate 15% improvement over the porous coated lamellar specimens.
A study of the nature and formation of zinc polyacrylate cement using Fourier transform infrared spectroscopy
Authors: Nicholson J. W. , Brookman P. J. , Lacy O. M. , Sayers G. S. , Wilson A. D.
Published: December 2004

The formation and structure of zinc polyacrylate has been studied by Fourier transform infrared spectroscopy (FTIR). Using this technique we have shown that the fully hardened cement is bonded predominantly by zinc carboxylate complexes, rather than by associations of purely ionic character as had previously been supposed. Ionic bonds are formed in the initial stages of the reaction but are gradually converted to complex forms. This bond rearrangement appears partly responsible for physical changes that occur during gelation, setting, and hardening.
The hydrolytic stability of mitrathane (a polyurethane urea)—an x‐ray photoelectron spectroscopy study
Authors: Paynter R. W. , Askill I. N. , Glick S. H. , Guidoin R.
Published: December 2004

The hydrolytic stability of microporous Mitrathane polyetherurethane urea vascular prostheses has been evaluated at pH 7 and pH 9, at 37°, 60°, and 80°C for time periods of up to 968 days. Mechanical strength was evaluated using a hydrodynamic burst test and surface chemical changes by x‐ray photoelectron spectroscopy. The samples held at 80°C showed the greatest mechanical strength loss which corresponded to the hydrolysis of the urethane groups. It was concluded that the gross in vivo surface degradation of Mitrathane prostheses, observed after six months, could not have been caused by simple chemical hydrolysis alone, as the polymer was found to be stable at 37°C for at least 11 months.
A model for the corrosion behavior of dental amalgams
Authors: Lemaitre L. , Moors M. , Van Peteghem A. P.
Published: December 2004

At high frequencies, electrochemical impedance behavior for corroding dental amalgams cannot be interpreted in terms of a simple Randles equivalent circuit. This may often be ascribed to the imperfect cell geometry resulting in a nonuniform current distribution. However, the insertion of a constant phase element (CPE) in the nonfaradaic branch of the equivalent circuit offers a new scope for interpretation as the circuit provides an m‐parameter corresponding to the degree of distortion. The decrease of m as a function of time was explained by a mathematical model reflecting an increasing number of pores. Moreover, that same model allows a better understanding of the passivating effect of NaHCO3 and of the differences between conventional and Cu‐rich dental amalgams.
Raman spectroscopy for the study of porous composite alumina coating
Authors: Bertoluzza A. , Fagnano C. , Tinti A. , Toni A. , Ciapetti G. , Sudanese A. , Cattaneo C.
Published: December 2004

A new acetabular cup prosthesis made of alumina and bioactive glass was studied and evaluated using nondestructive and noninvasive Raman laser spectroscopy. The prosthesis consists of an alumina socket coated with a double layer of alumina beads bonded to the prosthesis with a layer of glass. Raman spectroscopy showed that both the socket and the beads are composed of α‐Al2O3 (corundum), while the bioactive glass (alkaline and alkaline earth alumosilicate with a small quantity of zirconium oxide) showed this to have an intermediate structure between that of vitreous silica and that of the alkaline and alkaline earth disilicate glasses. The Raman spectra of the contact surfaces between the bioactive glass and the alumina of the assembled prosthesis and of an alumina disk coated with the same glass showed the presence of new bands which may be correlated with a chemical interaction between the components of the prosthesis.
Fatigue of acrylic bone cement–effect of frequency and environment
Authors: Johnson J. A. , Provan J. W. , Krygier J. J. , Chan K. H. , Miller J.
Published: December 2004

This study was conducted to investigate some fundamental fatigue testing variables as they apply to the response characteristics of acrylic bone cement. Cyclic loading under load control was conducted at frequencies of 1, 2, 5, 10, and 20 Hz in air at room temperature. At a tensile stress range of 0.3–20.0 MPa the fatigue life increased linearly with logarithmic frequency. The effect of conditioning and testing in saline at both room temperature and 37°C at similar stress levels and a frequency of 10 Hz were also examined. When compared to dry testing at room temperature, testing in saline at 37°C resulted in a reduction in fatigue life while testing in saline at room temperature produced an increase in fatigue life. Of a number of statistical distributions considered, the Weibull was found to be the most appropriate in documenting the findings of this investigation. A companion fractographic investigation of the failure surfaces demonstrated distinct regions of crack growth and fast fracture.
Ultrastructural comparisons of ceramic and titanium dental implants in vivo: A scanning electron microscopic study
Authors: Steflik David E. , McKinney Ralph V. , Koth David L.
Published: December 2004

Identically prepared, screw‐type ceramic and titanium endosteal dental implants were inserted in the jaws of adult mongrel dogs for periods of up to 6 months. Sixteen of the 32 total implants supported fixed bridgework. The interface of bone and soft connective tissues with the dental implants was examined by routine and innovative scanning electron microscopic (SEM) techniques using both secondary and backscattered electron imaging. Results demonstrated excellent bone adaptation to both titanium and ceramic implants. Direct adaptation of bone to the upper third of both type implants was observed with only minimal amounts of any intervening fibrous connective tissue. A composite of trabecular bone and fibrous connective tissue was observed in the lower two‐thirds of the implants examined. Areas of bone alteration suggestive of osteoid were observed at the thread apicis of some loaded implants. From this investigation we concluded that similar longitudinal tissue responses were generated to one‐piece, cylindrical screw‐type titanium and alpha alumina oxide ceramic dental implants. Possible bone remodeling was observed at the thread apicis of the loaded implants, an area where occlusal forces may be distributed. We further suggest that one‐stage endosteal implants are capable of maintaining a proportional bone‐to‐implant interface at the apical support region, similar to that suggested to two‐stage implant systems.
Immunological safety assessments of anti‐IgE antibody which is detached from therapeutic immunoadsorbents for removing IgE
Authors: Sato Hiroshi , Kidaka Teruhisa
Published: December 2004

Assessments were made of the safety of antibodies which might be detached from a therapeutic immunoadsorbent (IA) during extracorporeal circulation, with respect to possible immunological responses to such antibodies. The IA used was antihuman IgE antibody (a‐IgE Ab) immobilized on a carrier, for removal of IgE from patients' plasma. The antibody was raised in goats and isolated to give an IgG fraction. This fraction was either used without further purification or was subjected to immunoaffinity purification. The active anaphylaxis test in guinea pigs indicated that positive responses were not observed at doses of less than 0.1 μg of goat IgG per animal. Rabbits given goat IgG intravenously 3 times a week for 8 weeks did not produce the specific antibody against goat IgG at doses of less than 0.05 μg/kg, which corresponds to less than 3 μg for an adult with a body weight of 60 kg. However, none of the rabbits given goat IgG at 2.5 mg/kg showed any toxic reactions and different patterns of the body weight growth from these in the control group. In addition, we tested whether immunoaffinity purified a‐IgE Ab could trigger Type I hypersensitivity in a monkey model. Anaphylactic reactions were not observed after a single intravenous injection of a‐IgE Ab at less than 10 μg/kg. These in vivo results are useful to judge whether the amount of antibody that leaks from a therapeutic IA is acceptable or not in a clinical situtation.
Apatite–Wollastonite containing glass ceramic granule–fibrin mixture as a bone graft filler: Use with low granular density
Authors: Ono Kozo , Yamamuro Takao , Nakamura Takashi , Kokubo Tadashi
Published: December 2004

The purpose of this study was to investigate bone formation after implantation of a mixture of apatite—wollastonite containing glass ceramic granules (A–W.GC, 220–355 μm) and fibrin glue with a low A–W.GC granular density. The fibrinogen was prepared from rat blood plasma. A mixture of A–W.GC granules and fibrin glue 1:4 in volume ratio (1:4 mixture) was implanted in the proximal metaphysis of the rat tibia, and bone formation was evaluated quantitatively by histomorphometry in undecalcified specimens. Microangiography was performed in animals sacrificed 5 days after the operation. The results were compared with those of a previous study in which a 1:1 mixture of A–W.GC granules and fibrin glue was used. With the 1:4 mixture, the A–W.GC density was 39.7% because of concentration of fibrin at packing. Good early vascularization comparable to that after implantation of the 1:1 mixture was observed. Bone formation proceeded at the same rate as after implantation of 1:1 mixture, but the level of the plateau was higher than that for the 1:1 mixture. The osteoconductive potential of the 1:4 A–W.GC‐fibrin mixture was similar to that of the 1:1 mixture, and was higher than that of A–W.GC without fibrin.
Exclusion of uropathogen adhesion to polymer surfaces by Lactobacillus acidophilus
Authors: Hawthorn Lesley Ann , Reid Gregor
Published: December 2004

The ability of bacteria to adhere to surfaces is a major cause of concern in the use of biomaterial substrates. The adhesion of Staphylococcus epidermidis strain 1938 was examined using image analysis and was found not to correlate with polymer surface tension, unlike that of Lactobacillus acidophilus, which adhered to more hydrophobic polymers. A fimbriated uropathogenic E. coli strain showed very low levels of adherence to the biomaterials. Precoating the polymers with lactobacilli significantly reduced the staphylococcal and E. coli adhesion, a result which could have clinical significance. An additional finding was that the interaction of staphylococci and E. coli with lactobacilli coated polymers altered the adhesion profile of the latter. Lactobacilli appeared to detach from polymers of low surface tension and reattach to polymers with high surface tensions. This resulted in the highest levels of exclusion of uropathogens being found for lactobacilli‐coated glass and sulfonated polystyrene, both of which are hydrophilic (with high surface tensions). These results demonstrate that lactobacilli can be used to coat biomaterial surfaces leading to a reduced adhesion of uropathogens.
Cyclic fatigue‐crack propagation, stress‐corrosion, and fracture‐toughness behavior in pyrolytic carbon‐coated graphite for prosthetic heart valve applications
Authors: Ritchie R. O. , Dauskardt R. H. , Yu Weikang , Brendzel A. M.
Published: December 2004

Fracture‐mechanics tests were performed to characterize the cyclic fatigue, stress‐corrosion cracking, and fracture‐toughness behavior of a pyrolytic carbon‐coated graphite composite material used in the manufacture of cardiac valve prostheses. Testing was carried out using compact tension C(T) samples containing “atomically” sharp precracks, both in room‐temperature air and principally in a simulated physiological environment of 37°C Ringer's lactate solution. Under sustained (monotonic) loads, the composite exhibited resistancecurve behavior, with a fracture toughness (KIc) between 1.1 and 1.9 MPa √m, and subcritical stress‐corrosion crack velocities (da/dt) which were a function of the stress intensityKraised to the 74th power (over the range ∼10−9to over 10−5m/s). More importantly, contrary to common perception, under cyclic loading conditions the composite was found to display true (cyclic) fatigue failure in both environments; fatigue‐crack growth rates (da/dN) were seen to be a function of the 19th power of the stress‐intensity range ΔK(over the range ∼10−11to over 10−8m/cycle). As subcritical crack velocities under cyclic loading were found to be many orders of magnitude faster than those measured under equivalent monotonic loads and to occur at typically 45% lower stress‐intensity levels, cyclic fatigue in pyrolytic carbon‐coated graphite is reasoned to be a vital consideration in the design and life‐prediction procedures of prosthetic devices manufactured from this material.
A new porous polyetherurethane wound covering
Authors: Bruin P. , Jonkman M. F. , Meijer H. J. , Pennings A. J.
Published: December 2004

A polyetherurethane (PEU) wound covering with non‐interconnected micropores up to approximately 5 μm has been prepared by means of a phase inversion process. This highly elastic, very thin (15–20 μm), pliable wound covering showed good, immediate adherence to wet wound surfaces and high water vapor permeability, but was impermeable to bacteria. In guinea pigs epidermal wound healing of partial‐thickness wounds under PEU wound coverings was accelerated compared with uncovered controls and an occlusive wound covering, OpSite. Water in liquid form or wound exudate could not leak through the PEU covering, but its high water vapor permeability induced concentration of the wound exudate into a jellylike clot layer, which apparently accelerated reepithelialization. The main conclusion from a clinical study on 20 donor sites was that the use of the PEU covering reduced pain, besides prevention of fluid retention. No differences in epithelialization were seen in comparison to tulle gras‐treated wounds.
Dynamic mechanical properties of multiphase acrylic systems
Authors: Øysæd Harry
Published: December 2004

The influence of type and quantity of five different dimethacrylate crosslinking agents on the dynamic mechanical properties of multiphase acrylic systems has been studied. These materials, commonly used in bioengineering, were processed by polymerization of a mixture of liquid methacrylate monomers, and poly(methyl methacrylate) powder. The specimens were made with various ratios of methyl methacrylate and dimethacrylate crosslinking agents in the monomer liquid. Two different processing conditions were used, heat‐polymerization at 100°C and autopolymerization at 45°C. By using a forced torsional vibration apparatus the storage modulus (G′), loss modulus (G″), and dissipation factor (tan δ) were determined over the temperature range −60°C to 140°C at frequencies of 0.1, 1.0, 10, and 100 rad/s. In the autopolymerized materials, the glass transition temperature (Tg), as determined via tan δ data, increased with increasing quantities of crosslinking agents. The storage modulus likewise increased. In the heat‐polymerized materials only minor variations in modulus and tan δ with type and quantity of crosslinking agents were observed. Tg values of the heat‐polymerized materials were, in all cases, greater than those of the autopolymerized materials.
A new canine model to evaluate the biological response of intramedullary bone to implant materials and surfaces
Authors: Spivak Jeffrey M. , Ricci John L. , Blumenthal Norman C. , Alexander Harold
Published: December 2004

A new canine model utilizing an implantable chamber with multiple bone in‐growth channels has been used to study the response of intramedullary bone to various implant materials and surfaces.

The first group of dogs received implants containing channels lined by smooth‐surfaced coupons of titanium, titanium alloy, sputter‐hydroxyapatite‐coated (HA‐coated) titanium alloy, and polyethylene. A pattern of early initial bone ingrowth by 2 weeks, becoming maximal at 6 to 12 weeks with remodeling to a more mature lamellar bone, and later resorption by 24 weeks was seen for all test groups, with fibrous tissue interfaces covering the smooth test coupons at all time points. Significantly increased bone ingrowth in the sputter‐HA coated group was found only at 6 weeks.

The second group of dogs received implants with channels lined by surfaceroughened coupons of either titanium or plasma‐HA‐coated titanium, half of which were also packed with a crystalline‐HA grouting at the time of surgery. At both 6 and 12 weeks, bone ingrowth was greatly enhanced by the presence of the plasma‐HA coating or the crystalline‐HA grouting as compared to the uncoated titanium channels. Histologically, bone was seen to bond directly to the plasma‐HA coating and the crystalline‐HA grouting. A thin fibrous tissue layer was noted between bone and the titanium in most areas, but evidence of direct bone contact to the metal surface was seen. Mechanical testing in tension of intact coupon‐‐bone‐‐coupon units revealed significant strength of the bone‐‐plasma‐‐HA bond, with failure initiating at the metal‐HA interface with forces of 15.3 N at 6 weeks, increasing to 44.8 N at 12 weeks. Plasma‐HA‐lined channels with crystalline‐HA packing required similar forces for failure. No significant adhesion strength was noted for the titanium channels at 6 weeks, and only the crystalline‐HA‐filled channels displayed measurable strength of the bone‐‐titanium interface at 12 weeks, with a force of 9 N needed for failure.
Adherence of HDPE powder coating on Co‐Cr surfaces: Effect of substrate preparation and gas sterilization
Authors: Laberger M. , Drouin G. , Gélinas C. , Champagne B. , Bobyn J. D.
Published: December 2004

As part of the development of a hemiarthroplasty implant with a compliant surface layer, the effect of surface preparation of a cast Co‐Cr alloy substrate on the adhesion of a polymeric coating was studied. High‐density polyethylene (HDPE) coatings were deposited on Co‐Cr alloys without adhesive by spraying powder onto the surface of specimens maintained at a controlled temperature. Prior to deposition, two different types of surface preparation were carried out: chemical etching and grit‐blasting. Adherence tests were performed in order to study the effect of the surface preparation of a Co‐Cr alloy on the adherence of the HDPE film. The etching process enhanced the adherence by a factor of 10 compared to the grit‐blasting process. For coatings deposited on grit‐blasted Co‐Cr surfaces, rupture occurred at the interface (adhesive mode) as well as in the coating (cohesive mode). A full cohesive mode was observed for films deposited on etched surfaces. Gas sterilization with an ethylene oxide and Freon 12 solution did not change significantly the adherence of the film deposited on etched surfaces. Examination of the surfaces indicated that the etching process created a specific type of porosity consisting of dendritic cavities whereas grit‐blasting produced surface irregularities. Cavities produced by etching were larger that the polymer powder particles and could be easily filled. The coating of an ethced Co‐Cr alloy substrate with a layer of HDPE provided an interface that could probably sustain the physiological loading in a normal synovial joint.
Exposure to mercury vapor during setting, removing, and polishing amalgam restorations
Authors: Haikel Y. , Gasser P. , Salek P. , Voegel J. C.
Published: December 2004

The level of mercury vapors in the oral cavity was determined by analyzing 242 samples of intra‐oral air before and after removing, setting, and polishing dental amalgam. The analysis was effected using atomic absorption spectrometry in cold vapors with the detection limit of 6 μg/m3. A score of 1 to 3 was assigned to each restoration to adjust the differences of the amalgam sizes. The present study showed that the vapor was released during any procedure: removing, setting, and polishing amalgam. The mean levels were between 85 and 326 μg/m3. However, before the restorative procedures, no mercury vapors had been detected in the oral cavity. This investigation has also demonstrated a significant direct correlation between Hg vapor concentrations in intra‐oral air and the sizes of amalgam restorations during each procedure: removing, setting, and polishing. The statistic analysis showed no significant difference of mercury vapors in the oral cavity between the use or nonuse of water coolant during the amalgam polishing.
Amount and surface structure of albumin adsorbed to solid substrata with different wettabilities in a parallel plate flow cell
Authors: Uyen H. M. W. , Schakenraad J. M. , Sjollema J. , Noordmans J. , Jongebloed W. L. , Stokroos I. , Busscher H. J.
Published: December 2004

In this article we studied the adsorption of serum albumin to substrata with a broad range of wettabilities from solutions with protein concentrations between 0.03 and 3.00 mg · mL−1 in a parallel‐plate flow cell. Wall shear rates were varied between 20 and 2000 s−1. The amount of albumin adsorbed in a stationary state was always highest on PTFE, the most hydrophobic material employed and decreased with increasing wettability of the substrata. Increasing stationary amounts of adsorbed albumin were observed with increasing wall shear rates at the lowest protein concentration. Inverse observations were made at the highest protein concentration. Transmission electron micrographs of replicas from the albumin‐coated substrata showed that proteins were mostly adsorbed in islandlike structures on the hydrophobic substrata. The tendency to form islandlike structures was shear rate‐ and concentration‐dependent and disappeared gradually going to more hydrophilic substrata. On glass, the most hydrophilic material employed, a homogeneous, well distributed, fine knotted, reticulated structure was found. In conclusion, this study demonstrates that both the amount of adsorbed albumin as well as the surface structure of the adsorbed proteins are regulated by the substratum wettability. This observation may well account for the fact that substratum properties can be transferred by an adsorbed protein film to the interface with adhering cells or microorganisms.
Prevention of bioprosthetic heart valve tissue calcification by charge modification: Effects of protamine binding by formaldehyde3
Authors: Golomb Gershon , Ezra Vitoria
Published: December 2004

Calcification is the principal cause of the clinical failure of bioprosthetic heart valves (BHV). Calcification occurs through an interaction of host and implant factors, mainly younger age and glutaraldehyde pretreatment, respectively. The hypothesis of this work was that an impaired balance between positively and negatively charged amino acids, due to the reaction with Lys and Hyl tissue‐collagen residues, expose affinity sites to Ca++. We further hypothesized that regardless of the cause(s) of BHV calcification, positive charge modification of the tissues will prevent their propensity to calcify. Modification of BHV tissue was obtained by covalently binding protamine sulfate, a polybasic peptide, via formaldehyde and subsequent glutaraldehyde tissue crosslinking. Protamine‐bound tissue exhibited stability properties (shrinkage temperature and resistance to collagenase digestion) similar to BHV tissue. Protamine‐treated tissue was less permeable to Ca++, and reduced staining was observed with positively charged dyes, indicating the presence of positively charged functional groups in the modified tissue. Significant prevention of calcification was exhibited by the p‐bound tissue in comparison to BHV tissue, 30.9 and 109 μg/mg calcium, respectively, after 30 days of subdermal implants in rats. The modification procedure resulted in stable, covalent links of approximately 10% w/w protamine with undiminished anticalcification properties, even after 1 year storage. The results support our hypotheses, and orthotopical heart valve replacements are required in order to completely evaluate the treatment efficacy and bio‐compatibility.
The effect of the extracorporeal shock wave lithotriptor on bone cement
Authors: Schreurs B. W. , Bierkens A. F. , Huiskes R. , Hendrikx A. J. M. , Slooff T. J. J. H.
Published: December 2004

For the purpose of studying its applicability for acrylic cement removal during total hip revision surgery, experiments with an extracorporeal shock wave lithotriptor were carried out. High‐energy shock waves (HESW) were focussed on discs of polymethylmethacrylate bone cement. The average discharge was 18.1 kV; the number of shock waves 0, 100, 250, 500, 1000, and 2000; the application rate was 85 shocks/min. Macroscopic or radiographic effects were not in evidence. Microscopically, typical lesions in a small concentric focal area with a diameter of 8.5 (± 2.5) mm were found. The individual lesions were smaller than 0.1 mm, and displayed characteristic shapes. The area porosity increased with the number of shocks. The maximal area porosity caused by the HESW, measured by quantitative microscopy, was 4% after 2000 shock waves. The lesions were also studied by scanning electron microscopy. It can be concluded that HESW causes only microscopic lesions on the frontal surface of discs of bone cement, and that these lesions are small compared to the pores normally present in bone cement, when applied clinically.
Use of collagen film as a dural substitute: Preliminary animal studies
Authors: Collins Ronald L. L. , Christiansen David , Zazanis George A. , Silver Frederick H.
Published: December 2004

Cadaver grafts, laminated metallic materials, and synthetic fabrics have been evaluated as dural substitutes. Use of cadaver tissues is limited by fear of transmission of infectious disease while use of synthetic materials is associated with implant encapsulation and foreign body reactions. The purpose of this study is to evaluate the use of collagen film as a dural substitute. Collagen films prepared from bovine skin were used to replace the dura of rabbits and histological observations were made at 16, 28, 42, and 56 days postimplantation. Controls consisted of dura that was removed and then reattached. Control dura showed no signs of inflammation or adhesion to underlying tissue at 16 and 28 days postimplantation. By 56 days postimplantation, extensive connective tissue deposition was observed in close proximity to adjacent bone as well as pia arachnoid adhesions. Implanted collagen film behaved in a similar manner to control dura showing minimal inflammatory response at all time periods. At 56 days postimplantation collagen film appeared strongly infiltrated by connective tissue cells that deposited new collagen. The results of this study suggest that a reconstituted type I collagen film crosslinked with cyanamide acts as a temporary barrier preventing loss of fluid and adhesion formation. It is replaced after approximately 2 months with host collagen with limited inflammatory and fibrotic complications. Further studies are needed to completely characterize the new connective tissue formed as well as long‐term biocompatibility and functioning of a reconstituted collagen dural substitute.
The importance of the diffusive transfer of tints in the technology of tinting of soft contact lenses
Authors: Polishchuk A. Ya. , Iordanskii A. L. , Zaikov G. E. , Varshavsky V. L. , Yagodkina T. A. , Dubova I. G. , Madyuskin N. N.
Published: December 2004

This paper deals with the kinetics of tint transfer in soft contact lenses. A mathematical model taking into account both diffusion and chemical reactions is proposed and physicochemical parameters are determined. It is shown that bulk tinting is more effective in practice than surface tinting.
Effect of silicone rubber surface on the calcium balance of human serum
Authors: Rosanova Irina , Sevastianov Victor , Kim Sung Wan
Published: December 2004

The nature and mechanism of calcium complexation with human serum components in the presence of silicone rubber were assessed in in vitro model experiments. Silicone rubber samples were incubated for 67 h in serum of both physiologic calcium concentrations and induced hypercalcemic levels. Physiologic calcium incubation decreased the intrinsic and nth binding site association constants by factors of 2 and 4, respectively, from initial serum values. Incubation with silicone rubber did not change the association constants. Hypercalcemia incubation lowered the intrinsic and nth binding site association constants by 39 and 61%, respectively. Polymer incubation increased the intrinsic association constant and decreased the number of binding sites by a factor of 2. With initial binding site association constants unperturbed by incubation and Hill coefficients equivalent to 1, complexation was noncooperative and binding sites were considered to be identical and independent. Both Scatchard and Hill plots show nonlinearity for the polymer incubation case giving two distinct linear regions. This is indicative of cooperative binding for incubation with polymer; the Hill coefficient for the physiologic calcium concentration range was 0.97, while the coefficient for the hypercalcemic calcium range was 6.
A study of the fatigue properties of small diameter wires used in intramuscular electrodes
Authors: Scheiner Avram , Thomas Mortimer J. , Kicher Thomas P.
Published: December 2004

Single and multi‐strand stainless steel and cobalt‐nickel alloy wires, with strand diameters from 26 to 46 μm, were fatigue tested using a modified rotating bending test to determine what factors are most important in controlling fatigue life. The relation between cyclic strain and cyclic life was determined for each material by cyclically straining test specimens at various strain ranges and recording the number of cycles to failure. The results show that (a) the fatigue curves of the 316LVM, MP35N, DBS, and Syntacoben wires are very similar and have many of the same fatigue characteristics of specimens of large cross section. (b) Multi‐stranded wires have the same average fatigue life as their individual constituent strands but the variance of that life is smaller (c) Deformities in the wire, which are created during the manufacturing, appear to have the effect of shortening the fatigue life of these small section wires. (d) Observation of wire fracture surfaces show a relatively small crack propagation zone and a large fast fracture zone suggesting that most of the fatigue life of these small wires is in the original crack formation, which creates a large stress concentration and quickly leads to wire failure, (e) The size of the wire cross sectional area is of secondary importance compared to the amplitude of the maximum cyclic strain of the individual strands in determining fatigue life of the cable. To maximize the fatigue life of electrodes in vivo, the highest fatigue life for a given bending radius of curvature is desired. This suggests wire strands should be manufactured at the smallest diameter possible (without introducing structural flaws) to maximize service life.
Student research award in the graduate degree candidate category, 17th annual meeting of the society for biomaterials, scottsdale, AZ may 1–5,1991. A mechanical investigation of fluorapatite, magnesiumwhitlockite, and hydroxylapatite plasma‐sprayed coatings in goats
Authors: Dhert W. J. A. , Klein C. P. A. T. , Wolke J. G. C. , van der Velde E. A. , de Groot K. , Rozing P. M.
Published: December 2004

Ceramic coatings of fluorapatite (FA), magnesiumwhitlockite (MW), and hydroxylapatite (HA), and noncoated Ti‐6Al‐4V alloy (Ti) implants were evaluated before and after implantation in an animal study. Cylindrical plugs were coated by plasma‐spraying with FA, MW, and HA. X‐ray‐diffraction patterns showed for FA and HA a crystalline and for MW, an amorphous‐crystalline coating structure. The plugs were implanted into the right femora and left humeri of 16 adult goats. Follow‐up periods were 12 and 25 weeks. The in vivo results were evaluated using push‐out tests and scanning electron microscopy. There were significant differences in push‐out strengths between femur and humerus. The FA and HA implants showed significantly higher push‐out strengths than the MW and Ti alloy implants, especially for the 12 week follow‐up period. Furthermore, at 12 week follow‐up period. Furthermore, at 12 weeks, MW showed significantly lower push‐out strengths than Ti alloy. SEM‐investigation of the interfaces revealed that FA did not degrade while both MW and HA showed extensive degradation at 12 and 25 weeks. In addition, the interface after push‐out testing showed for the MW, HA, and Ti alloy implants to be fractured at the implant‐tissue interface and for the FA to be fractured at the coating‐titanium interface.
Materials for enhancing cell adhesion by immobilization of cell‐adhesive peptide
Authors: Ito Yoshihiro , Kajihara Masako , Imanishi Yukio
Published: December 2004

Materials to enhance cell adhesion were synthesized by surface integration of peptide, Arg‐Gly‐Asp‐Ser(RGDS), which is an active‐site sequence of cell‐adhesive proteins. Polystyrene film was glowdischarged and graft‐copolymerized with acrylic acid. Then the peptide was immobilized to the poly(acrylic acid) grafts by using water‐soluble carbodimide. The cell‐adhesive activity of the RGDS‐immobilized film increased with increasing amount of immobilized peptide, and approached the activity of fibronectin(FN)‐immobilized film. The RGDS‐immobilized film was more stable against heat treatment and pH variation than the FN‐immobilized film. In addition, the RGDS‐immobilized film enhanced cell growth more strongly than the FN‐immobilized film.
Evaluation of biocompatibility, based on quantitative determination of the vascular response induced by material implantation
Authors: Bouet T. , Toyoda K. , Ikarashi Y. , Uchima T. , Nakamura A. , Tsuchiya T. , Takahashi M. , Eloy R.
Published: December 2004

The biocompatibility of nine different materials, including positive and negative references, 4 polyurethane based and 3 latex based materials was investigated by (1) cytotoxic assay using V79 Chinese hamster cells, (2) the thickness of inflammatory layer at 3 and 7 days after intramuscular implantation test, and (3) the course of the blood flow in tissue reaction around subcutaneously implanted materials using Laser Doppler Flowmetry (LDF) over 14 days following implantation. In addition, for some materials, different modes of sterilization were compared. Although the three methods explore different reactive systems, the material ranking obtained was highly similar for the three methods, suggesting a relative accuracy between them. For one latex however, an absence of cytotoxic effect in culture and a highly intense response by LDF investigation of the same order of magnitude as for the positive reference implant suggest that bioincompatibility may result from the material itself and cannot be exclusively investigated by the leaching of toxic components.
On the fractography of overload, stress corrosion, and cyclic fatigue failures in pyrolytic‐carbon materials used in prosthetic heart‐valve devices
Authors: Ritchie R. O. , Dauskardt R. H. , Pennisi F. J.
Published: December 2004

A scanning electron microscopy study is reported of the nature and morphology of fracture surfaces in pyrocarbons commonly used for the manufacture of mechanical heart‐valve prostheses. Specifically, silicon‐alloyed low‐temperature‐isotropic (LT1)‐pyrolytic carbon is examined, both as a coating on graphite and as a monolithic material, following overload, stress corrosion (static fatigue), and cyclic fatigue failures in a simulated physiological environment of 37°C Ringer's solution. It is found that, in contrast to most metallic materials yet in keeping with many ceramics, there are no distinct fracture morphologies in pyrocarbons which are characteristic of a specific mode of loading; fracture surfaces appear to be identical for both catastrophic and subcritical crack growth under either sustained or cyclic loading. We conclude that caution should be used in assigning the likely cause of failure of pyrolytic carbon heart‐valve components using fractographic examination.
Degradation of medical‐grade polyurethane elastomers: The effect of hydrogen peroxide in vitro
Authors: Meijs Gordon F. , McCarthy Simon J. , Rizzardo Ezio , Chen Yi‐Chi , Chatelier Ronald C. , Brandwood Arthur , Schindhelm Klaus
Published: December 2004

Treatment of Pellethane 2363‐80A—a medical‐grade poly(tetramethylene oxide)‐based polyurethane elastomer—with 25% (w/w) hydrogen peroxide at 100°C for times ranging from 24 h to 336 h led to significant decreases in ultimate tensile properties and decreases in molecular weight, both at the surface and in the bulk. IR spectral changes were similar to those observed after degradation in vivo. Differential scanning calorimetry showed that hydrogen‐peroxideinduced degradation was associated with greater order in the hard domain and greater mobility in the soft domain. Studies conducted with low‐molecular‐weight model compounds for the hard and soft segments confirmed that methylene groups adjacent to oxygen were susceptible toward oxidation. The extent of degradation of a series of commercial polyurethanes on treatment with hydrogen peroxide (25%, 24 h, 100°C) correlated well with their reported susceptibility to environmental stress cracking in vivo. © 1993 John Wiley & Sons, Inc.
Metal ion concentrations in retrieved polyethylene total hip inserts and implications for artifactually high readings in tissue
Authors: Meldrum Russell D. , Bloebaum Roy D. , Dorr Lawrence D.
Published: December 2004

Although there are many studies which document high metal ion concentrations in clinically retrieved tissues surrounding total joint replacements, most investigations have remained cautious in their interpretation due to the artifactual influences of metal particulate.

The possible contribution of polyethylene wear debris to artifactually high periprosthetic metal ion concentration readings has not been previously considered. This study documents the potential role of polyethylene particulate contamination in causing artifactually high metal concentration readings in tissues.

The data showed metal ion contamination in the polyethylene was progressive at each stage of exposure to metal: from bar stock preparation, to manufacturing, to in vivo ambulation. The manufacturing and machining processes showed a statistically significant (P ≤ .05) increase in metal ion concentrations in the nonarticulated acetabular inserts over bar stock.

The results of this study demonstrate that periprosthetic tissue and synovial fluid metal ion concentration data must be interpreted with caution due to possible artifactual problems associated with metal ion contaminated polyethylene particulate. © 1993 John Wiley & Sons, Inc.