bluuebunny/crossref_metadata_2025 huggingface dataset:
Microheterophase structure, permeability, and biocompatibility of A‐B‐A triblock copolymer membranes composed of poly(γ‐ethyl L‐glutamate) as the A component and polybutadiene as the B component
Authors: Sato H. , Nakajima A. , Hayashi T. , Chen G.‐W. , Noishiki Y.
Published: December 2004

A‐B‐A block copolymers (EBE) consisting of poly(γ‐ethyl L‐glutamate) as the A component and polybutadiene as the B component were synthesized. The microheterophase structure of these block copolymers, as observed microscopically, was less distinct than that of the block copolymer (GBG) composed of poly(γ‐benzyl L‐glutamate) as the A component. This was attributed to the better compatibility of the ethyl group with polybutadiene block, compared with the benzyl group. The observed micelle size of various microheterophase structures ranged from 350 to 480 Å, which agreed well with the micelle size estimated from a thermodynamic study. From the measurement of water permeation through the EBE block copolymer membranes, the contributions of the interfacial region between the α‐helical polypeptide domain and polybutadiene domain to the permeability coefficient were concluded to be higher than those of poly(γ‐methyl L‐glutamate)‐polybutadiene block copolymer (MBM) membranes, i.e., more hydrophilic domain seemed to exist in EBE membranes than in MBM membranes. The results of in vivo tests on the tissue compatibility indicate that the EBE block copolymer membranes have good biocompatibility.
The removal of residuals and oligomers from poly(2‐hydroxyethylmethacrylate)
Authors: Brynda E. , Štol M. , Chytrý V. , Cífková I.
Published: December 2004

Poly(2‐hydroxyethyl methacrylate) gels obtained by the cross‐linking polymerization using four different free‐radical initiators were washed with water. Chromatographically, the eluate appeared to be a mixture of low‐molecular‐weight compounds and of a small amount of the high‐molecular‐weight component. The UV and IR absorption spectra of compounds present in the eluate were compared with those of model compounds that were assumed to exist in the gel as impurities after the polymerization (monomers and oligomers of hydroxyethyl methacrylate, decomposition products of initiators). Time dependences of the removal of impurities from the gels by washing were measured. Most of the impurities were washed out within a few hours. In addition to the assumed impurities, the eluate was found to contain an unidentified compound that was still washed out after several months. Intracutaneous applications of this compound did not produce local irritation of the tested tissue.
Alginate dental impression materials: Chemistry, structure, and properties
Authors: Cook Wayne
Published: December 2004

The setting behavior of calcium alginate impression materials was investigated by monitoring the viscosity, calcium ion activity, and shear modulus during the reaction. Structural information was also obtained from the dependence of viscosity and compressive modulus on the calcium concentration in model systems. The gelation time is primarily controlled by the concentration of Na4P2O7 in solution acting as a retarder, while the level and particle size of the alginate and CaSO4 · 2H2O also affect the kinetics through the dissolution rates and concentration effects. The Ca2+ crosslinks bridging the alginate chains in the network appear to be labile. Although this process of bond interchange and that of continued polymerization during deformation may be contributory mechanisms to permanent set, bond rupture appears to be the primary mechanism. Bond rupture can be reduced by increasing the alginate content in the system which also raises the tear energy. Both the permanent set and tear energy are affected by the filler particle morphology.
Adhesion behavior of rat lymphocyte subpopulations (B cell and T cell) on the surface of polystyrene/polypeptide graft copolymer
Authors: Maeda Mizuo , Kimura Masatoshi , Inoue Shohei , Kataoka Kazunori , Okano Teruo , Sakurai Yasuhisa
Published: December 2004

Polyvinyl/polypeptide graft copolymers having microdomain structure on their surfaces were newly synthesized for the development of a specific cell separator, and the adhesion behavior of rat lymphnode lymphocytes with these materials was examined by column method. Morphologic change of lymphocytes adherent to the graft copolymers was found to be less than that of cells adherent to corresponding homopolymers, i.e., polystyrene and poly(γ‐benzyl L‐glutamate). Separation of lymphocyte subpopulations (B cell and T cell) was examined in the absence of serum proteins. The adhesion selectivity for B cell was found to depend on the microdomain structure, since the highest value, 2,2, was observed for the graft copolymer with the polypeptide content of 50 wt%. Synthetic polypeptide derivatives may be promising materials which substitute for a conventional system with nylon fiber and fetal calf serum.
In vivo biocompatibility studies. VII. Inflammatory response to polyethylene and to a cytotoxic polyvinylchloride
Authors: Marchant R. E. , Anderson J. M. , Dillingham E. O.
Published: December 2004

The cellular biocompatibility of low‐density polyethylene and a cytotoxic polyvinylchloride were investigated using an in vivo cage implant system. Components of the inflammatory response (white cells, extracellular alkaline and acid phosphatase, the complement component C3, and total protein content) were monitored over a 21‐day implantation period. Scanning electron microscopy was used to evaluate the morphologic condition of leukocytes adherent to the implanted polymers. Prior to implantation, each polymer was evaluated using an established primary acute toxicity screen. The results showed that the cytotoxic polyvinylchloride stimulated an intense acute phase inflammatory response, and at later observation periods, an intense and increasing chronic inflammatory response. In constrast, the polyethylene promoted relatively small increases in the acute and chronic phases of inflammation; the overall cellular response being essentially resolved by the third week after implantation. The initial toxicity screen of each polymer suggested that the observed differences in inflammation were primarily caused by the release from the polyvinylchloride of the added cytotoxic agent (dioctyltinbisoctylmercaptoacetate).
Bioerodible polyanhydrides as drug‐carrier matrices. II. Biocompatibility and chemical reactivity
Authors: Leong K. W. , D'Amore P. , Marletta M. , Langer R.
Published: December 2004

The biocompatibility of bioerodible polyanhydrides and toxicology of the polymer breakdown products were assessed. Poly‐[bis (p‐carboxy‐phenoxy) propane anhydride] (PCPP), Poly(terephthalic acid anhydride) (PTA), and their copolymers with sebacic acid were tested. The polymers did not provoke inflammatory responses in the corneas of rabbits over a six week implantation period. Subcutaneous implantation studies of PCPP in rats over a six month period showed no evidence of inflammatory cells and only slight tissue encapsulation by layers of fibroblastic cells. The degradation products of the polymers were nonmutagenic, noncytotoxic, and had a low teratogenic potential. The in vitro growth of mammalian cells on the polymers was unaffected as measured by cell morphology and cell growth rate. The chemical reactivity of the polyanhydrides with reactive model drugs, para substituted anilines, was also examined. Amides were formed when the drugs were injection molded with the polyanhydrides at 120°C. However, no reaction was observed using compression molding at room temperature. No reaction occurred between the polymer and the drug during the hydrolytic degradation of the matrix at 37°C.
Use of tricalcium phosphate or electrical stimulation to enhance the bone–porous implant interface
Authors: Berry J. L. , Geiger J. M. , Moran J. M. , Skraba J. S. , Greenwald A. S.
Published: December 2004

Implant stabilization by biologic ingrowth into a porous surface offers a durable method of prosthetic fixation. These systems, however, lack the immediate stability offered by the use of acrylic bone cement. The interface strength of porous coated CoCrMo in a canine model does not approach that of acrylic bone cement until two weeks postoperatively. It is expected that this would be a minimum time period in clinical applications. Both chemical and electrical means have been advocated as methods to affect tissue ingrowth. A study using a canine model was undertaken to determine tissue ingrowth rates utilizing examples of these two methods: (1) impregnation of the porous structures with tricalcium phosphate powder (TCP); or (2) the application of an electrical stimulator to the implant with the implant itself serving as the cathode. Ten implants were coated with TCP, two each at weekly intervals from 1 to 5 weeks. Plain porous rods were likewise implanted, serving as the controls. While histology did reveal a slightly more dense bony structure, the interface bond strength was not affected by TCP. Electrical stimulation of the implant was similarly investigated with an additional time period of 10 weeks. Compared to the controls, the electrically stimulated implants reveal no statistically demonstratable difference in interface strength. Histologic specimens indicate larger areas of calcification than are observed in the controls.
A comparative study of the biologic and immunologic response to medical devices derived from dermal collagen
Authors: DeLustro Frank , Condell Richard A. , Nguyen Mai Anh , McPherson John M.
Published: December 2004

We examined collagen materials for soft tissue augmentation [Zyderm® Collagen Implant (ZCI), glutaraldehyde cross‐linked (GAX) collagen, and Koken Atelocollagen (Atelocollagen)]; hemostatic collagens [Gelfoam® Gelatin Powder (Gelfoam), Avitene® Microfibrillar Collagen Hemostat (Avitene), and Collastat® Collagen Hemostat (Collastat)]; and reconstituted, intact fibrillar collagen from bovine skin in a subcutaneous guinea pig model. After 11, 25, and 39 days in situ, explants from animals injected with GAX collagen demonstrated greater wet‐weight persistence than all other materials. Conversely, at all time points, the explants of Atelocollagen were the least persistent. Following 25 days in vivo, explants were examined using differential scanning calorimetry; ZCI and Atelocollagen displayed thermal transition temperatures of 58°C. Avitene and Gelfoam explants displayed transition points of 30°C and 32°C, indicating denatured or cleaved collagen. By contrast, GAX collagen explants had a high (68°C) transition temperature, reflecting its cross‐linking. With respect to immunogenicity, day 39 sera from ZCI treated animals showed significantly lower titers in the ELISA to their respective implant collagen than all other groups examined, while antibody activity in the GAX collagen, Gelfoam, Atelocollagen, and intact collagen groups were not significantly different. Collastat elicited antibodies with a greater affinity than observed in these previous groups. Sera from Avitene treated animals demonstrated the highest antibody levels and were the only sera which reacted with bovine serum albumin. Thus, Avitene was the most immunogenic of the collagen materials examined, while GAX collagen demonstrated the greatest persistence and minimal immunogenicity, and ZCI was the least immunogenic.
Fracture toughness determination of dental amalgams through microindentation
Authors: Hassan R. , Vaidyanathan T. K. , Schulman A.
Published: December 2004

A microindentation technique was used to study and estimate the fracture toughness of six amalgams. A significant difference is observed between fracture toughness at the bulk and the margin of amalgams. All amalgams show significant differences in fracture toughness as a function of distance from the margin. Microindentation measurement of fracture toughness appears to be an effective method of evaluating the localized brittleness of amalgams.
Clinical study of urokinase‐bound fibrocollagenous tubes
Authors: Senatore Fred , Bernath Fred , Meisner Ken
Published: December 2004

Dacron‐reinforced fibrocollagenous tubes (FCT) were synthesized from canine mongrels using the mandril‐rod technique in order to develop a small diameter (i.e., 4 mm i.d.) vascular graft. They were rendered fibrinolytic by immobilizing urokinase on to the inner surface of the tubes. Urokinase‐bound fibrocollagenous tubes (UK‐FCT), control FCTs (i.e., no bound enzyme), Perloff grafts (Dr. Perloff, Department of Surgery, University Medical Center, Sidney Australia, has developed a mandril‐derived collagenous tube from goats. Samples were implanted for comparative purposes.) and autogeneous saphenous veins, were interposed in the carotid or femoral artery in chronic studies involving 21 canine mongrels. On the basis of Doppler auscultation and palpation, the UK‐FCTs were statistically more patent than other candidate prostheses. Fibrin degradation product (FDP) increased in the dogs' systemic circulation with a postoperative peak of 5 days. The host's increase in fibrinolytic activity was shown to be local to the anastamosis. A carotid arterial extracorporeal shunt was designed to evaluate acute patency. Results indicated a rapid thrombosis but no platlet or fibrin adherence to the graft surface was observed, as evidenced by scanning electron microscopy.
Synthesis and bioevaluation of a rapidly biodegradable tissue adhesive: 1,2‐Isopropylidene glyceryl 2‐cyanoacrylate
Authors: Jaffe H. , Wade C. W. R. , Hegyeli A. F. , Rice R. M. , Hodge J.
Published: December 2004

A rapidly biodegradable tissue adhesive, 1,2‐isopropylidene glyceryl 2‐cyanoacrylate, was synthesized and characterized by NMR. Bond strength was determined. Three types of corresponding polymers were prepared and evaluated for in vitro and in vivo toxicity. The polymers were generally found to be in the moderately toxic and toxic groups similar to the lower alkyl 2‐cyanoacrylates.
Thrombin uptake and inhibition on endothelium and surfaces with a stable heparin coating: A comparative in vitro study
Authors: Arnander C. , Dryjski M. , Larsson R. , Olsson P. , Swedenborg J.
Published: December 2004

The endothelial lining and two differently heparin‐coated surfaces were compared in vitro regarding thrombin uptake and inhibition. One heparin surface was based on stabilized ionic binding of heparin, the other on covalent binding of partially degraded heparin. Both heparin surfaces have previously been shown to have pronounced thromboresistant properties. The two heparinized polyethylene surfaces and the endothelial surface of segments of the porcine aorta were studied. After exposure to the surfaces, thrombin disappeared from the solution and appeared bound to the surfaces. The disappearance rate of thrombin from the solution was the same on exposure to the endothelium and the covalently bonded heparin surface, but less following exposure to the ionically bonded heparin surface. The thrombin activity appearing on the endothelium was lower than on the heparin surfaces, indicating that the endothelium exerted a slow thrombin inhibiting capacity. On exposure of the thrombin‐loaded endothelium to plasma, thrombin was rapidly inhibited. Thrombin bound to the covalently bonded heparin surface was inhibited at a slower rate than on the ionically bonded surface, but still faster than the rate at which free thrombin was inhibited in nonheparinized plasma. It is concluded that the endothelium and stabilized heparin coatings bind thrombin and accelerate its inhibition by plasma.
In vitro calcification and in vivo biocompatibility of the cross‐linked polypentapeptide of elastin
Authors: Wood S. A. , Lemons J. E. , Prasad K. U. , Urry D. W.
Published: December 2004

The in vitro calcifiability and molecular weight dependence of calcification of the polypentapeptide, (L · Val1‐L· Pro2‐Gly3‐L · Val4‐Gly5)n, which had been γ‐irradiation cross‐linked have been determined when exposed to dialyzates of normal, nonaugmented fetal bovine serum. The material was found to calcify: calcifiability was found to be highly molecular weight dependent and to be most favored when the highest molecular weight polymers (n ≈240) had been used for cross‐linking. The in vivo biocompatibility, biodegradability, and calcifiability of the γ‐irradiation cross‐linked polypentapeptide were examined in rabbits in both soft and hard tissue sites. The material was found to be biocompatible irrespective of its physical form and to be biodegradable but with n of 200 or less it was not shown to calcify or ossify in the rabbit tibial nonunion model.
Retrieval and analysis of a clinical total artificial heart
Authors: Coleman Dennis L. , Meuzelaar Henk L. C. , Kessler Thomas R. , McClennen William H. , Richards Joe M. , Gregonis Donald E.
Published: December 2004

Examination by light microscopy, scanning electron microscopy (SEM), and x‐ray microanalysis of a clinical total artificial heart (TAH) implanted for 112 days revealed no evidence of calcification, pannus, or vegetative thrombus. A macroscopic thrombus was seen along the suture line in the right atrium but did not obstruct blood flow or valve function. Microscopic thrombi (<0.1 mm) and evidence of microemboli were observed on the pumping diaphragm using SEM. Characterization of selected polyetherurethane (PEU) samples from the pumping bladders and housing by Curie‐point pyrolysis mass spectrometry (Py‐MS) revealed unexpected differences between postmortem retrieved ventricles. Although the origin of these differences could be traced back to batch‐to‐batch variations in the original PEU material (Biomer), the precise nature of the observed differences in chemical structure and/or composition is still unknown. Numerical comparison between pyrolysis mass spectra from PEU samples exposed to blood or tissue and unexposed samples from the same ventricles did not detect evidence of biodegradation. Continual improvements in fabrication and quality control should minimize surface imperfections and ensure polymer reproducibility; however, existing materials and design parameters appear to be adequate for continued clinical implantation.
Preserved and foreign cartilage interpositional materials for silastic finger joint implant arthroplasty
Authors: Powers Dennis L. , Gaisser David M. , Barton Quentelle
Published: December 2004

Cartilage grafts were implanted as interpositional materials (IPMs) around the stems of silicone finger joint prostheses to protect their surfaces from abrasion with the local bone tissue. The knee joints of New Zealand White rabbits were implanted with finger joint prostheses and grafted with preserved auto‐ and allografts as well as fresh xenografts. Data were obtained after one month and compared to controls that received only the silicone prostheses. The grafting procedures did not cause any variations in joint function or differences in the amount of lipids absorbed by the prosthesis. A thin fibrous capsule formed about the control implants, whereas the capsules of the grafted legs were greater in thickness and area. Gross examination of the implant surfaces, weight analyses, and light microscopic studies of the number of wear particles found in the surrounding tissue capsules all indicated a reduction in prosthetic wear with grafting. The cartilage grafts were surrounded by inflammatory cells and were losing their proteoglycans. As expected, the xenografts exhibited the most degradation. No differences were noted between the preserved grafts. These results indicate that at one month, cartilage has provided protection for early implant motion. The biodegradable graft was being replaced by fibrous connective tissue. Long‐term protection needs to be studied in additional experiments.
The influence of static stress on the corrosion behavior of 316L stainless steel in Ringer's solution
Authors: Bundy K. J. , Vogelbaum M. A. , Desai V. H.
Published: December 2004

The decrease in corrosion resistance of 316L stainless steel due to static stress was studied in vitro using a 37°C Ringer's solution electrolyte. Both potentiodynamic polarization and coulometric techniques were used. Cyclic anodic polarization tests with highly loaded fracture mechanics samples revealed a lowering of breakdown potential and disruption of passive films compared to unstressed controls. Measurements of the time‐averaged current density due to a 100 mV anodic overpotential showed that a stress level causing plastic deformation increases the current density by more than an order of magnitude compared to samples stressed to the yield stress or nonloaded controls. The significance of these findings for surgical implant devices in service is discussed.
Adhesion of coagulase‐negative staphylococci to methacrylate polymers and copolymers
Authors: Hogt A. H. , Dankert J. , Feijen J.
Published: December 2004

Adhesion of coagulasef‐negative staphylococci (CNS) was studied onto a homologous series of methacrylate polymers and copolymers. The materials varied in wettability (contact angles) and were either positively or negatively charged (zetapotential). Bacterial adhesion experiments performed in a parallel‐plate perfusion system showed that positively charged TMAEMA‐Cl copolymers significantly promoted the adhesion of CNS as compared with all other methacrylate (co)polymers tested. The bacterial adhesion rates onto the positively charged surfaces are diffusion‐controlled, whereas those onto the surfaces with a negative zeta‐potential are more surface‐reaction‐controlled due to the presence of a potential energy barrier. The bacterial adhesion rates onto various poly (alkyl methacrylates) were similar. The number of adhering bacteria onto the negatively charged MMA/MAA copolymer did not differ from that onto pMMA, indicating that sufficient sites on the copolymer surface with the same potential energy barrier as that on pMMA, were available for adhesion. Decreasing rates of adhesion of CNS were observed onto MMA/HEMA copolymers with increasing HEMA content coinciding with increasing hydrophilicity. Low plateau values for the bacterial adhesion were observed on 50MMA/50HEMA, pHEMA, and 85HEMA/15MAA, indicating that the adhesion onto these materials was reversible. Four CNS strains with different surface characteristics all showed higher numbers of adhering bacteria onto 85MMA/15TMAEMA‐Cl than onto 85MMA/15MAA and pMMA.
Molecular and mechanical property changes during aging of bone cementin vitroandin vivo
Authors: Looney M. A. , Park J. B.
Published: December 2004

The changes in mechanical properties and free radical concentration of curing Simplex P Radiopaque Bone Cementin vivoandin vitroconditions were studied. Samples were prepared so that eachin vivosample that cured and aged in the canine femoral intramedullary cavities had anin vitrocounterpart that was cured and aged in a constant‐temperature saline bath at 37°C. An electron paramagnetic resonance (EPR) spectrometer was used to measure the growth and decay (curing) of polymerization radicals. The results of EPR measurements showed that the curing (disappearance of free radicals) ofin vivosamples takes a much longer time (more than 4 weeks) thanin vitrocuring (less than 2 weeks). The mechanical tests indicate that, whether agedin vivoorin vitro, the strength increased rapidly for the first 1–2 weeks and then slight increases were seen for up to 6 months.
Use of concentrated fibrinogen in experimental tracheal repair
Authors: Kram Harry B. , Hino Stanley T. , Harley Daniel P. , Fleming Arthur W. , Shoemaker William C.
Published: December 2004

Tracheal stenosis is a devastating complication of tracheal resection that may be related to improper suture selection and technique, as well as extensive surgical devascularization. This study evaluated Fibrin Sealant (FS) (Immuno AG, Vienna, Austria), a two‐component biologic adhesive, as a method for reducing the need for sutures in tracheal surgery. This adhesive has been found to be effective in face‐to‐face sealing of tissues, wound healing, and in establishing hemostasis. Six adult mongrel dogs underwent tracheal repair with FS. Three had tracheal hemitransections (approximately three quarters of the circumference) and were repaired using one absorbable suture and FS, and three had complete transections (with resection of two tracheal rings each) repaired using five absorbable sutures and FS. The animals were killed at varying intervals ranging from 6 h to 6 weeks. No animal had gross evidence of significant tracheal stenosis, and the endotracheal mucosa appeared well healed. We conclude that the use of FS in tracheal reconstruction results in a stable, leakless trachea, and that it significantly reduces the number of sutures needed; this may lead to a decreased potential for anastomotic ischemia and tracheal stenosis.
A model of thrombin inactivation in heparinized and nonheparinized tubes with consequences for thrombus formation
Authors: Basmadjian D. , Sefton M. V.
Published: December 2004

The role of flow and mass transport in determining procoagulant concentration at the wall of synthetic and natural cylindrical blood vessels is analyzed theoretically. The model assumes steady laminar flow and considers, in addition to the fluid dynamic parameters, three rate‐determining steps: production of procoagulant (thrombin) and its inactivation at the wall, as well as inactivation in the fluid bulk. The ratio of thrombin wall concentration to production rate Cw/N emerges as a critical parameter in characterizing the behavior of the tube wall. With a wall‐inactivation rate typical of heparinized materials, Cw/N = 11.1 s/cm, independent of flow (shear rate) and axial position. This is significantly less than the range of Cw/N (50–500 s/cm) for which the thrombin concentration is high enough to result in significant fibrin formation and thrombosis. Hence little fibrin formation and a high degree of thromboresistance is expected for heparinized materials. Nonheparinized materials have Cw/N values above this range, which are only weakly dependent on shear rate and diameter, suggesting that flow‐induced dispersion of thrombin (or other procoagulants) has limited impact on the thrombin wall concentration. These latter results appear to refute the conventional wisdom that attributes the relative patency of large‐diameter vesels and differences between venous and arterial thrombi to such flow effects. It is likely that additional factors such as flow pulsatility and wall geometry must be considered to account for these observations.
The influence of substratum surface free energy on growth and spreading of human fibroblasts in the presence and absence of serum proteins
Authors: Schakenraad J. M. , Busscher H. J. , Wildevuur C. R. H. , Arends J.
Published: December 2004

To determine whether the surface free energy of polymer materials influences the spreading and growth of cells, surface free energies of 13 polymers and glass were related to spreading and growth of human skin fibroblasts. Experiments were performed in both the presence and absence of serum proteins. We calculated the surface free energy from contact angles of phosphate‐buffered saline (PBS), n‐propanol/PBS mixtures, and α‐bromonaphthalene on the polymers, using the concept of polar and dispersion components accounting for spreading pressures. Cell spreading and substratum surface free energy (γs) showed a characteristic sigmoid relationship both in the presence and in the absence of serum proteins; good spreading only occurred when γs was higher than approximately 57 erg · cm−2. In the presence of serum proteins, cell spreading is similar on most materials; only few materials show relatively high cell spreading. Cell growth in the presence of serum proteins did not differ significantly on the various polymers with reference to their γs values. In contrast, two groups of polymers could be distinguished in the absence of serum with respect to cell growth. The first group showed increasing γs, whereas the second group showed consistently low cell growth. The results demonstrate the complex relationship between cell spreading and substratum surface free energy as well as the role of serum proteins in modifying the surface characteristics of polymers in relation to cell spreading and growth.
Displacements of precious and nonprecious dental bridges utilizing endosseous implants as distal abutments
Authors: Bidez M. W. , Lemons J. E. , Isenberg B. P.
Published: December 2004

An investigation was conducted to establish qualitative trends regarding the relative displacements exhibited by the distal and mesial abutments in a five‐unit fixed dental bridge as a function of bridge material and implant design utilized in the distal abutment site. Both Au and Ni‐based bridge systems utilizing double, natural‐tooth mesial abutments and three types of distal abutments (natural second molar, blade dental implant, and hollow‐basket implant) were tested on a dried human mandible and subjected to a controlled force applied distally. Dial gauges were positioned around each abutment site bilaterally to provide displacement data in the x (mesial/distal), y(buccal/lingual), and z(occlusal/gingival) directions. The results indicate some significant differences exist in the displacement profiles exhibited by the bridge systems as a function of both bridge material and abutment type.
The biocompatibility of solution cast and acetone‐extracted cast biomer
Authors: Marchant Roger E. , Anderson James M. , Hiltner Ann , Castillo E. J. , Gleit J. , Ratner B. D.
Published: December 2004

The cellular response to films of cast Biomer and acetone‐extracted Biomer were investigated over a 21‐day implantation period, using an in vivo cage implant system. Film samples were characterized by scanning electron microscopy (SEM), attenuated total reflectance infrared (ATRIR), electron spectroscopy for chemical analysis (ESCA) and by contact angle measurements before implantation, and by SEM and ESCA after implantation and cleaning. Cellular and protein components of the inflammatory response were analyzed at periodic observation points after implantation. In addition, film samples were retrieved at 4, 7, and 21 days after implantation and analyzed for leukocyte adhesion by light microscopy and SEM. The results demonstrated that cast Biomer contains an extractable fraction, which when removed significantly improves the biocompatibility of the material.
Dependence of curing time, peak temperature, and mechanical properties on the composition of bone cement
Authors: Brauer G. M. , Steinberger D. R. , Stansbury J. W.
Published: December 2004

Commercial bone cements usually contain hydroquinone as the polymerization inhibitor and N,N‐dimethyl‐p‐toluidine as the accelerator in the benzoyl peroxide‐initiated redox polymerization. The former compounds have certain shortcomings in their biocompatibility profile. Measurements of the setting times, polymerization exotherms, and postpolymerization strengths of the cured monomer‐polymer compositions show that the hydroquinone can be replaced by food grade di‐tert‐butyl‐p‐cresol (BHT). The more reactive 4‐N,N‐(dimethylamino)phenethanol can replace 4‐N,N‐dimethyl‐p‐toluidine, yielding cements with shorter setting times and increased strengths. Excessive heat liberated on polymerization can be reduced by partial substitution of higher‐molecular‐weight methacrylates, e.g., dicyclopentenyloxyethyl methacrylate for methyl methacrylate, but there is a decrease in strength of the resulting polymer. More successful has been the addition to the monomer of 1% or 2% of the chain transfer agent pentaerythritol tetra(3‐mercapto‐propionate), which lowers the peak temperature without changing the physical properties of the cement. Compositions with short curing times, lower exotherms, and mechanical properties that exceed those of a commercial material have been formulated.
Adhesion behavior of rat lymphocytes to poly(ether)–poly(amino acid) block and graft copolymers
Authors: Yokoyama Masayuki , Nakahashi Takeshi , Nishimura Takao , Maeda Mizuo , Inoue Shohei , Kataoka Kazunori , Sakurai Yasuhisa
Published: December 2004

Block and graft copolymers consisting of poly(ether) and poly(amino acid) were synthesized, and adhesion behavior of rat lymphocytes to the surface of the film made from these copolymers was analyzed by the microsphere column method. Poly(ethylene glycol) (PEG) and poly(benzyl L‐glutamate) (PBLG) were used as poly(ether) and poly(amino acid), respectively. Adhesion behavior of lymphocytes was found to depend on the content and chain length of the components in these copolymers.
Hydrophilic‐hydrophobic microdomain surfaces having an ability to suppress platelet aggregation and their in vitro antithrombogenicity
Authors: Okano Teruo , Aoyagi Takao , Kataoka Kazunori , Abe Kazuhiko , Sakurai Yasuhisa , Shimada Masashi , Shinohara Isao
Published: December 2004

Block copolymers were synthesized by a coupling reaction of hydrophilic chains of poly(2‐hydroxyethyl methacrylate) (PHEMA) with hydrophobic chains of polystyrene (PSt), or poly(dimethyl siloxane) (PDMS). Microstructures of films of the block copolymers exhibited a hydrophilic‐hydrophobic microphase separated structure. For evaluation of in vivo antithrombogenicity, small diameter tubes (1.5 mm I. D. and 20 cm length) coated by the copolymers on their internal surfaces were implanted in rabbits as arteriovenous shunts. Occlusion times of the tubes, measured by formation of thrombus, were three days for PHEMA, two days for PSt, and three days for PDMS. The block copolymers showed excellent antithrombogenic properties: occlusion times were 20 days for HEMA‐St block copolymer and 12 days for HEMA‐DMS block copolymers. In vitro examination of polymer‐platelet interaction in terms of platelet adhesion and aggregation, which are important initial processes of blood coagulation, demonstrated suppressed adhesion and aggregation on microdomain surfaces constructed of hydrophilic and hydrophobic block copolymers. From both in vivo and in vitro examination, it was concluded that HEMA‐St and HEMA‐DMS block copolymers showed promising antithrombogenic activities by suppressing activation and aggregation of platelets.
Effect of microstructure of poly(propylene‐oxide)‐segmented polyamides on platelet adhesion
Authors: Yui Nobuhiko , Sanui Kohei , Ogata Naoya , Kataoka Kazunori , Okano Teruo , Sakurai Yasuhisa
Published: December 2004

The relationship between microstructure and platelet adhesivity of six types of poly(propylene oxide) (PPO)‐segmented polyamides based on the polyamide segments nylon 210, 310, 410, 510, 610, and 710 were investigated. These multiblock PPO‐segmented copolymers were prepared by interfacial polycondensation. Physical characterization of these copolymers was by means of thermal analysis, transmission electron microscope, wide‐angle X‐ray diffraction (WAXD), and small‐angle X‐ray scattering (SAXS). The WAXD and SAXS measurements showed that the copolymers had microstructures containing crystalline and amorphous phases and that these microstructures, represented by means of crystallite thickness and long period, varied with incorporation of PPO segments. Blood compatibility of these copolymers was evaluated by estimating the amount of adhering platelets on the copolymer surfaces. The amount of adhering platelets was minimum for the surfaces of the copolymers having a crystallite thickness of 6.0–6.5 nm and a long period of 12–13 nm. This result suggests that the particular size and distribution of the crystalline and amorphous phases in the copolymer could be determining factors for suppressing platelet adhesion on the copolymer surface, and that the control of these factors could lead to ideal antithrombogenic polymers.
Effect of pH on the microhardness of renal calculi
Authors: Johrde L. G. , Cocks F. H.
Published: December 2004

The effects of synthetic urine environments of pH 4, 6, and 9.5 on the microhardness of renal calculi have been investigated. Tests were made, using both Vickers and Knoop indenters, on three compositions of calculi: 100% calcium oxalate monohydrate (whewellite), 100% uric acid, and 98% magnesium ammonium phosphate hexahydrate (struvite) mixed with 2% carbonate apatite. Whewellite calculi hardness was lowered, relative to (dry) values by 45–55% when saturated with a solution of pH 9.5. Exposure to lower pH conditions was not as effective in lowering hardness in this case. Struvite calculi hardness was lowered by 41–52% compared to the dry hardness and uric acid calculi hardness decreased by 25–36%, compared to dry hardnesses. For uric acid stones the reduction in hardness did not depend on pH within the range of pH values investigated. For struvite stones, acid pH conditions appear to give an increased softening, compared to other pH values.
Synthesis of novel polyaminoetherurethaneureas and development of antithrombogenic material by their chemical modifications
Authors: Shibuta Ryuichi , Tanaka Masakazu , Sisido Masahiko , Imanishi Yukio
Published: December 2004

Novel polyaminoetherurethaneureas containing tertiary amino groups in the main chain were synthesized (PAEUU), quaternized (Q‐PAEUU), and heparinized (H‐PAEUU). Films of PAEUU showed a microphase separation, which was influenced by the quaternization and the heparinization. With increasing content of amino group, the water content of Q‐PAEUU and the heparin content of H‐PAEUU increased. The heparin‐releasing rate from H‐PAEUU into physiological saline solution was slow, but increased with increasing content of quaternary ammonium groups in the polymer. The water content, the heparin adsorption, and the heparin‐releasing rate were controlled by the kind of quaternizing agent. The antithrombogenicity of the polyurethaneureas was improved by quaternization and very much by heparinization, and affected by the kind of quaternizing agent. Heparinization was indispensable for achieving antithrombogenicity of the polymer, although the antithrombogenicity of H‐PAEUU was affected more strongly by the water content than by the heparin content. The surface free energy of these polymer films was also investigated.
The biological performance of calcium phosphate ceramics in an infected implantation site: I. Biological performance of hydroxyapatite during Staphylococcus aureus infection
Authors: Van Blitterswijk C. A. , Grote J. J. , De Groot K. , Daems W. Th. , Kuijpers W.
Published: December 2004

In the present study the biological performance of macroporous and dense hydroxyapatite after implantation in the rat middle ear was evaluated during an induced Staphylococcus aureus middle ear infection. The course of the infection was similar to that in the absence of an implant. Hydroxyapatite was frequently integrated with fibrous ingrowths in the middle ear lumen, originating solely from the infection. Good epithelial covering of the implant with all types of epithelial cells of importance for middle ear defence, was found. Increase of the exudate in the pores due to the infection was relatively small, and most of the exudate was restricted to pores on the implant surface. The bony tissue in the pores was not influenced significantly by the induced infection. Degradation of hydroxyapatite was consistent with earlier results obtained in the noninfected middle ear. The results obtained so far suggest that hydroxyapatite is highly suitable for middle ear implantation.
Synthesis and antithrombogenicity of polyetherurethaneurea containing quaternary ammonium groups in the side chains and of the polymer/heparin complex
Authors: Ito Yoshihiro , Sisido Masahiko , Imanishi Yukio
Published: December 2004

Novel polyetherurethaneureas containing tertiary amino groups in the side chains (PAEUU) were synthesized, quaternized with different alkyl halides (Q‐PAEUU), and heparinized (H‐PAEUU). The antithrombogenicity of PAEUU in vitro was improved by quaternization, and further by heparinization. The excellent antithrombogenicity of H‐PAEUU was controlled by the kind of quaternizing agent through the polar effect of quaternizing agent on the water content and through the steric effect of quaternizing agent on the heparin content of H‐PAEUU. The antithrombogenicity of H‐PAEUU was found to be affected by the water content more strongly than by the heparin content. H‐PAEUUs containing tertiary amino groups in the main chain, which were synthesized previously, showed a little better shortterm antithrombogenicity than the present H‐PAEUUs containing tertiary amino groups in the side chains. Since ammonium groups in the side chains of Q‐PAEUU impose little steric hindrance against the heparin adsorption, the release of heparin from the side chains of H‐PAEUU was slower but lasted longer than that from the main chain. Therefore, the present H‐PAEUU is expected to be a longterm antithrombogenic material.
In vitro testing of dental materials by means of macrophage cultures: II. Effects of particulate dental amalgams and their constituent phases on cultured macrophages
Authors: Syrjänen S. , Hensten‐Pettersen A. , Nilner K.
Published: December 2004

It is known that macrophages play an important role in the removal of foreign particulate matter from tissue. When powdered dental amalgam is introduced into the soft tissues an amalgam tattoo is formed due to the intracellular degradation of amalgam by macrophages and their polykaryons. It was therefore feasible to study the effects of particulate amalgams as well as their individual phases on macrophages in vitro. The parameters compared were rate of the phagocytosis, changes of cellular morphology, and release of lactate dehydrogenase (LDH) to demonstrate plasma membrane permeability. It was shown that all the alloys except the Sn8Hg particles (γ2‐phase) and γ2‐containing Revalloy were effectively phagocytized by macrophages, and the alterationsin cellular morphology were slight during the first day. Prominant cellular damage was seen in cultures treated with particulate Ag2Hg3 (γ1‐phase) and Revalloy for 1 week. A slight increase in LDH activity in the medium was seen one hour after the alloy treatment. The LDH activities due to the amalgam treatment increased in the order Dispersalloy < Revalloy < Sybraloy. Intraperitoneal phagocytosis did not cause any morphological changes in macrophages, but the per cent of phagocytosis was diminished.
Synthesis and antithrombogenicity of anionic polyurethanes and heparin‐bound polyurethanes
Authors: Ito Yoshihiro , Sisido Masahiko , Imanishi Yukio
Published: December 2004

Two kinds of novel antithrombogenic polyurethane materials were synthesized. One of them is a polyetherurethane with anionic charges on the film surface, and the other is a polyetherurethaneurea to which heparin was covalently bound. The mechanism of their antithrombogenicity was investigated. The anionic polyetherurethane selectively adsorbed albumin, did not cause a conformational change of plasma proteins adsorbed, and suppressed the adherence and deformation of platelets but did not deactivate the blood–clotting system, thus leading to a moderate antithrombogenicity. The heparin‐bound polyetherurethaneurea was not favorable for the selective adsorption of albumin, caused the denaturation of plasma proteins adsorbed, and induced the adherence and deformation of platelets but deactivated the blood‐clotting system, leading to excellent antithrombogenicity. For the investigation of blood‐material interaction, the importance of a multiparameter estimation of the activation of platelets and the blood‐clotting system was indicated.
Adsorption of plasma proteins to the derivatives of polyaminoetherurethaneurea: The effect of hydrogen‐bonding property of the material surface
Authors: Sanada Takashi , Ito Yoshihiro , Sisido Masahiko , Imanishi Yukio
Published: December 2004

Polyaminoetherurethaneureas bearing tertiary amino groups in the main chain (M‐PAEUU) were synthesized, quaternized (Q‐M‐PAEUU) and heparinized (H‐M‐PAEUU). With increasing portions of diisocyanate and with decreasing portions of polyaminoether in the feed, M‐PAEUU containing more hydrogen‐bonded urea carbonyl groups was prepared. With increasing hydrogen‐bonding character of M‐PAEUU, the adsorbed bovine serum albumin (BSA) was more denatured. By quaternization of M‐PAEUU, the protein adsorption increased, but the denaturation of adsorbed proteins was suppressed. With increasing ratio of hydrogen‐bonded urea carbonyl groups in Q‐M‐PAEUU, the adsorptions of BSA, bovine serum γ‐globulin (BγG), and bovine plasma fibrinogen (BPF) were decreased, but the degree of denaturation of adsorbed proteins was increased. In the adsorption to H‐M‐PAEUU, both the amount and the degree of denaturation of adsorbed proteins were strongly decreased. The dynamic adsorption experiments of plasma proteins showed the behaviors which are similar to the equilibrium adsorption experiments. The decrease of hydrogen‐bonded urea linkages and the increase of hydrophilicity by quaternization and heparinization of the polymer surface may be favorable for building up a hydration layer on the surface, thus suppressing the denaturation of plasma proteins which may trigger blood clotting and thrombus formation.
Elongation of brachymetatarsy with ceramic implant: A roentgenographic evaluation of its utility
Authors: Takaoka Kazuo Yonenobu Kunio , Tsuyuguchi Yuichi , Ono Keiro , Tada Koichi
Published: December 2004

The metatarsal bone was elongated by intercalary implantation of a single‐crystal alumina ceramic in 7 patients with brachymetatarsy. The implants were encased with new bone 24 months after surgery and resulted in 5.2 to 9.2 mm elongation of the metatarsal bone. The response of the bone to the ceramic implant was observed roentgenographically. No resorption or pseudoarthrosis of the bones, nor loosening or breakage of the implants, were observed. The alumina ceramic implant proved to be a useful substitute for a bone graft, because of its biocompatibility and strength.
Threaded versus porous‐surfaced designs for implant stabilization in bone‐endodontic implant model
Authors: Maniatopoulos C. , Pilliar R. M. , Smith D. C.
Published: December 2004

An endodontic implant model system was used to compare the effect of implant design on stabilization in bone. Specifically a porous‐surfaced design was compared to conventional threaded and smoothtapered endodontic implant designs. All implants were placed in immediate function thereby assessing the effect of early limited movement on the fixation achieved. A total of eighty‐three endodontic implants were inserted in the mandibles of six adult mongrel dogs. Animals were sacrificed immediately after implantation and after 3, 6, and 12 months. Implants were evaluated by clinical and radiographic examination and after animal sacrifice by pull‐out tests of the implant from the tissues, SEM examination of the pulled‐out implants and, finally, histology. The pull‐out test results indicated increasing shear strength with implantation time for the porous‐surfaced implants in contrast to the gradual loss of fixation for the threaded implants and the continuous low shear strength for the smooth implants. Histological studies and SEM examination indicated the reason for these changes. Smooth implants became encapsulated by fibrous connective tissue from early post‐implantation time periods. Threaded implants, although initially mechanically interlocked with bone, developed a fibrous connective tissue capsule that gradually thickened with time until, by 6 months, little mechanical interlock of bone and implant was present. It was assumed that this fibrous capsule thickening was caused by implant movement. The porous‐surfaced implants, however, became stabilized by bone ingrowth and showed more extensive bone formation within the surface pores with time. It is concluded that for implants that are made functional immediately after implantation, as in this study, porous‐surfaced implants can become strongly fixed by bone ingrowth, in contrast to conventional threaded or smooth‐surfaced designs, thus presenting a more favourable long term prognosis.