bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evolution of the mandibular mesh implant
Authors: Salyer Kenneth E. , Johns Donnell F. , Holmes Ralph E. , Layton James G. 
Published: December 2004

AbstractBetween 1960 and 1972, the Dallas Veterans Administration Hospital Maxillofacial Research Laboratory developed and made over 150 cast‐mesh implants. Successive designs were ovoid, circular, and double‐lumened in cross section to improve implant strength, surface area for bioattachment, and adjustability. Sleeves, collars, and bows were employed in the assembly of these implants, with an acrylic condylar head attached when indicated. In 1972, our laboratory developed a mandibular mesh tray, cast in one piece on a single sprue, with preservation of the vertically adjustable ramus. Stainless steel replaced Vitallium because of its greater malleability. Essentially, a lost‐wax technique is used to cast the mesh tray. The model of a mandibular segment is duplicated as a refractory model. Mesh wax, made in our own custom‐made die, is adapted to the refractory model. The unit is then sprued and invested. The wax is fired our of the mold in a gas furnace. Casting is done by the transferral of molten stainless steel from the crucible to the mold by centrifugal force in an electroinduction casting machine. Other mesh implants that have been developed are made from wire mesh, Dacron mesh, cast Ticonium, and hydroformed titanium.
Evaluation of wound‐covering materials
Authors: Schwope A. D. , Wise D. L. , Sell K. W. , Dressler D. P. , Skornick W. A. 
Published: December 2004

AbstractPhysical and in vivo (burned rat model) evaluations as wound coverings were performed for 1) a freeze‐dried collagen/poly (ϵ‐caprolactone) (PCL) film laminate, 2) a freeze‐dried PCL “foam”/PCL film laminate, and 3) a heat‐dried collagen/PCL film laminate. Porcine skin and cadaver skin were also evalulated in vivo for the purpose of comparison. Water‐vapor transmission rates and Young's moduli were measured. The degrees of adherence of the coverings to the wound were measured. Grafts which became significantly adherent (>150 dyne/cm2) to the wound within 1 day were most successful in promoting the formation of a viable tissue bed which appeared ready to accept further grafting. The force required to remove the PCL foam laminate from a full‐thickness excision wound was found to increase from 170 dyne/cm2 on the first day postgraft to 1500 dyne/cm2 by the tenth day. The force required to remove freeze‐dried collagen laminate remained constant at 200 dyne/cm2 over the 10 day test period. For the heat‐dried collagen laminate, a force of only 50 dyne/cm2 was required on day 1, increasing to 200 dyne/cm2 on day 6. Insensible water‐loss rates of animals grafted with the laminates were found to be similar to those from animals with human cadaver skin grafts and less than that from animals with porcine skin grafts. When moistened, the laminates prepared using the freeze‐dried materials were flexible and somewhat transparent permitting observation of the wound.
Analysis of the ingredients and determination of the residual components of acrylic bone cements
Authors: Brauer G. M. , Termini D. J. , Dickson G. 
Published: December 2004

AbstractRapid and reliable methods for the characterization and quantitative determination of ingredients usually present in self‐curing methacrylate bone cements were developed using spectrophotometric, gas chromatographic (GC), and conventional gravimetric procedures. These procedures are applicable to non‐crosslinked methacrylate resins. In the presence of some copolymers, polymer blends or crosslinking agents, or other ingredients which will result in the formation of insoluble methacrylate resins, some modification of the identification procedures and quantitative estimation of the resin components will be required. Molecular weight and molecular weight distribution of the powder and cured cement were obtained from viscosity and gel‐permeation measurements. Residual low molecular weight materials in the cured cement were determined for various storage times. Residual and water‐leachable monomer and residual dimethyl‐p‐toluidine (DMPT) were measured by GC. In air, the monomer content of the cured resin decreased from 3.3% after 1 hr to 2.4% after 215 days. When stored in water at 37°C, over 65% of the extractable monomer is leached out within 10 min. After 6 hr, the rate of diffusion of monomer into the aqueous phase is low. The cured cement contains as much as 0.6% DMPT, which does not leach out. Residual peroxide, estimated spectrophotometrically, amounts to 0.8%, but decreases to 0.14% after 15 months in water at 37°C. A semiquantitative colorimetric test indicated that the hydroquinone content of specimens analyzed within 24 hr after curing amounted to 9 ppm.
Effect of comonomer ratio on hydrocortisone diffusion from sustained‐release composite capsules
Authors: Fu J. C. , Moyer D. L. , Hagemeier C. 
Published: December 2004

AbstractThe daily in vitro release of hydrocortisone from composite polymer capsules is reported here for over 120 days. Increase in vinyl acetate comonomer content of the ethylene–vinyl acetate copolymer matrix brought about an increase in the diffusion rate. Variation in the initial drug content of the capsules from 40 mg to 20 mg affects the daily drug release less significantly than the variation in copolymer ratio. The correlation between vinyl acetate comonomer content and the percent crystallinity of the copolymer matrix is suggested as one of the possible major factors in controlling diffusion rate from this drug–polymer system. The diffusion constant (D) calculated was 0.212 × 10−10 cm2/sec when the copolymer carrier has 30% vinyl acetate content and 0.430 × 10−11 cm2/sec when the copolymer carrier has 20% vinyl acetate content for capsules with 20 mg initial drug content, and 0.118 × 10−11 cm2/sec and 0.226 × 10−11 cm2/sec, respectively, for capsules with 40 mg initial drug content.
Thrombus formation in a staged capillary membrane oxygenator associated with a microaggregate blood filter: A scanning electron microscope study
Authors: Guidoin R. G. , Awad J. A. , Domurado D. , Haggis G. H. 
Published: December 2004

AbstractBlood contact at interfaces in extracorporeal devices is a source of traumas. Proteins are very rapidly adsorbed; then, depending on which proteins are left various degrees of platelet aggregation follow and thrombi develop. The scanning electron microscope reveals very instructive information on the morphology of the blood deposits which adhere to foreign surfaces. Oxygenators such as the Awad D, which is a staged one made of silicone rubber, become “thrombus invaded” after prolonged extracorporeal circulation in spite of adequate heparinization of the blood. In most cases, evaluation of membranes and devices is assessed with respect to transfer of blood gases. Careful examination of the morphology of deposits should be developed. This study shows the importance of blood flow rate, design, and materials.
Antiinflammatory activities of polymers of o‐methacryloyloxybenzoic acid
Authors: Grimová J. , Hrabák F. 
Published: December 2004

AbstractAntiinflammatory activities of low‐ and high‐ molecular‐weight polymers of o‐methacryloyloxybenzoic acid were compared with the antiinflammatory activity of o‐acetoxybenzoic (acetylsalicylic) acid in tests on hind‐leg inflammations in rats induced by injection of either Freund's adjuvant or aqueous suspension of kaolin. The antiinflammatory activies of the orally administered polymers cooresponded to 40–90% of the activity of o‐acetoxybenzoic acid, and were not substantially dependent on the degree of polymerization.
Experimental infections along subcutaneous conduits
Authors: Myojin Kazuhiro , Von Recum Andreas F. 
Published: December 2004

AbstractTo determine whether progressive infection along percutaneous conduits (PC) usually leads to infection of cardiac assist devices, two PCs each were implanted into the subcutis of 11 dogs. One month later, one end of one conduit was inoculated with either E. coli or S. aureus. The resulting infections in all dogs progressed little during the first two weeks and in 10 of the 11 animals involved less than 40% of the total length of the PC. Bacteriological tests one month after the infecting organisms were introduced showed that they were no longer present at the site of inoculation in 4 of the 11 dogs and no bacteria were found at the opposite end of the inoculated PCs or in the noninoculated PCs. Histological observations confirmed these results and indicated that in all animals encapsulation of the infected area prevented its further enlargement.
Identification of wear particles in tissue after implantation of different plastic materials
Authors: Leugering H. J. , Püschner H. 
Published: December 2004

AbstractA method is shown by which to identify wear particles of implanted plastic materials in tissue. A Mettler FP2 hot stage was used to determine the melting point of different elastomer particles in normal histological sections between the crossed nicols. By using a microcolorimeter Type MPE (Leitz, Wetzlar, Germany), additional information about the molecular degradation of wear particles was obtained.
Antibiotics in acrylic bone cement. In vitro studies
Authors: Welch Ardyce B. 
Published: December 2004

AbstractThe effect of combining gentamicin and cephalothin with Surgical Simplex bone cement was tested in vitro. Experiments were designed to determine (1) quantitative elution rates and period of time the antibiotics were eluted and (2) effective bactericidal qualities. Both antibiotics were eluted from polymerized acrylic cement in large quantities within 24–48 hr after coming in contact with fluid and continued to be released in smaller amounts for 21 days to more than 175 days. This varied with the antibiotic, concentration of antibiotic in the cement, surface area of cement, and volume of elution fluid. Quantitative determinations of numbers of bacteria in broth cultures demonstrated that sufficient quantities of antibiotics were released to be bactericidal to microorganisms within 45 min to 20 hr. This was dependent on the type of antibiotic, type of bacteria, concentration of antibiotic in the cement, and time of contact.
Age hardening of orthodontic beta titanium alloys
Authors: Goldberg A. Jon , Shastry C. V. 
Published: December 2004

AbstractMetastable beta titanium alloys have been shown to be effective in orthodontic therapy because of their low modulus of elasticity and good springback, forming, and welding characteristics. Although used in the as‐drawn condition, these alloys are also age hardenable through precipitation of the alpha phase in the beta matrix. The effect of aging temperature, aging time, and prior cold work on the mechanical properties of fine wires of Ti‐13V‐11Cr‐3Al and Ti‐11.5Mo‐6Zr‐4.5Sn were determined. The latter alloy was more responsive to aging. Aging at 900°F for 14 h produced increases of approximately 40% in the modulus of elasticity, the yield and ultimate strengths. There was a corresponding decrease in ductility. The resulting wires could be useful in clinical situations requiring a high‐yield strength and a stiffness intermediate between as‐drawn beta titanium and stainless steel, the elastic moduli of which are 10 and 28 × 106 psi, respectively.
Enzyme histochemistry of the tissue response to pure metal implants
Authors: McNamara A. , Williams D. F. 
Published: December 2004

AbstractTechniques of enzyme histochemistry have been used to augment those of histology and scanning electron microscopy in the study of the tissue response to pure metals. In this article the distribution of acid and alkaline phosphatase, lactate and succinate dehydrogenases, leucine aminopeptidase, and nonspecific esterase in association with implants of aluminium, copper, cobalt, nickel, and lead is described, and its significance for the tissue response is discussed. The toxic nature of cobalt was demonstrated especially by the intense acid phosphatase activity associated with macrophages and the virtual absence of LDH and SDH activity, implying a low level of respiration. Pigmented deposits noted previously from histological examination of the tissue surrounding copper implants was shown to be cellular in origin with many individual cells of macrophagic morphology being discernible following histochemical staining, suggesting that pigmentation has resulted from copper overload, similar to that of liver cells in Wilson's Disease. Generally, observations with nickel were qualitatively similar to those with copper, but not so prominent. Although lead is well known as a toxic metal, and indeed its effect on nervous tissue was apparent in this study from observation of unusual enzyme activity in muscle, the local response was minimal in contrast to that associated with several other pure metals. On the other hand, aluminium, normally considered a relatively nontoxic metal, induced intense activity of certain enzymes, noticeably acid phosphatase and leucine aminopeptidase, indicating its toxicity under implant conditions.
Cell growth on metallic glasses: The interaction of amorphous metal alloys with cultured neuronal, osteoblast, endothelial, and fibroblast cells
Authors: McAuslan B. R. , Johnson G. , Delamore G. W. , Gibson M. A. , Steele J. G. 
Published: December 2004

AbstractFerrous based, corrosion resistant amorphous alloys supported the adhesion and growth of cultured chick neuronal cells, human marrow stromal cells (presumptive osteoblasts), bovine aortal endothelial cells, and hamster kidney fibroblasts. Alloys of compositions Fe60Ni10Cr10P13C7, Fe70Cr10P13C7, and Fe70Cr10P13B7 were found to be suitable. In contrast the crystalline form of these alloys was markedly less effective. Outgrowth of neurites from neuronal cells was promoted by precoating the metal surface with either laminin or neurite promotion factor. The adhesion of osteoblasts and fibroblasts suggests that corrosion resistant metal glasses should be considered as biomaterials useful for orthopedic applications. The adhesion of neuronal cells accompanied by neurite outgrowth indicates that the system might provide a functional interface between the neuromuscular system and an electromagnetic material that could be useful in bionic engineering.
Polymerization of multifunctional methacrylates and acrylates
Authors: Miyazaki Koji , Horibe Takashi 
Published: December 2004

AbstractThe cross‐linking reaction of 15 dimethacrylates, one trimethacrylate and five diacrylates was studied by means of differential scanning calorimetry (DSC) and high performance liquid chromatography (HPLC) to investigate the relationship between the polymerization characteristics and the chemical structure of these monomers. The amount of pendant double bonds (Dp) and the efficiency of cross‐linking (Ec) were calculated from both the extent of polymerization (Ep) and the amount of residual monomer (Rm) obtained by DSC and HPLC analyses, respectively. The Ep and Ec values of various monomers increased with an increase in the number of chain members between the functional groups, while Rm and Dp values decreased. The dimethacrylates consisting of aliphatic chains polymerized more readily than those containing aromatic units. High Ep was obtained in the aliphatic dimethacrylates and diacrylates with more than eight chain members and the aromatic dimethacrylates with more than 20 chain members among the monomers examined. These results depend presumably on the flexibility of the functional groups in the polymer network. With most dimethacrylates and diacrylates, high Ep was also observed in thermal scanning polymerization compared to isothermal polymerization at 90°C. The diacrylates showed a high rate of polymerization compared to the corresponding dimethacrylates.
Poly(dimethylsiloxane)‐poly(ethylene oxide)‐heparin block copolymers III: Surface and bulk compositional differences
Authors: Grainger D. W. , Okano T. , Kim S. W. , Castner D. G. , Ratner B. D. , Briggs D. , Sung Y. K. 
Published: December 2004

AbstractPreviously observed bioactivity of poly(dimethylsiloxane)‐poly(ethyelene oxide)‐heparin (PDMS‐PEO‐Hep) triblock copolymers has prompted studies of the surface and bulk character of this copolymer using angular‐dependent electron spectroscopy for chemical analysis (ADESCA), static secondary mass spectroscopy (SIMS), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Because the low‐energy PDMS phase dominates surfaces of this copolymer when solvent cast under air or vacuum conditions, attempts were made to explain surface restructuring and rearrangements induced in hydrated or aqueous environments that permit surface accessibility and bioactivity of heparin moieties. Based on comparisons with PDMS, PEO, and heparin homopolymers, PEO/heparin blends, and an unheparinized PDMS‐PEO diblock copolymer, PDMS‐PEO‐heparin demonstrates both phase‐mixed and phase‐separated regions in DSC analysis. During annealing cycles above the Tg values of the copolymer constituents, phase‐mixed regions become increasingly phase separated and PEO enriched. TGA analysis confirmed the presence of block copolymer constituents and presented evidence of intermolecular segmental interactions, hence phase‐mixing in the copolymers. ADESCA analysis indicates that the outer 5 Å of both the PDMS‐PEO and PDMS‐PEO‐Hep copolymers is essentially pure PDMS. However, significant amounts of PEO are detected 5 to 20 Å below the surface. Static SIMS also detects the presence of PDMS at the surfaces of the PDMS‐PEO and PDMS‐PEO‐Hep copolymers. Compositional models based on ADESCA, SIMS, and DSC data are presented for desiccated and hydrated copolymer surfaces.
Stress enhancement and fatigue susceptibility of porous coated Ti‐6Al‐4V implants: An elastic analysis
Authors: Messersmith Phillip B. , Cooke Francis W. 
Published: December 2004

AbstractAn elastic stress analysis of porous‐coated implant surfaces was performed using the finite element method. Three‐hundred‐μm‐diameter metal beads sinter bonded onto an implant surface were modeled with sinter neck radii of 5, 10, 20, and 50 μm. Smooth‐surface, single‐bead, single‐layer, and double‐layer systems were analyzed. The finite element models were loaded to simulate bone–bead contact forces and lateral hip implant tensile forces. Results showed that, for a single bead sinter‐bonded onto an implant surface, concentration of stress occurs either at the base of the sinter neck or within the neck itself, depending on the type of loád applied. Under lateral hip implant tensile loads, a maximum stress concentration factor of 1.97 was obtained for a single bead sinter‐bonded onto a implant surface. Addition of a single layer of beads onto the implant surface resulted in a significant increase in stress at the most proximal and distal ends of the porous layer, with a maximum stress concentration factor of 4.3. Addition of a second layer of beads did not significantly increase the magnitude of the stress concentration occurring at the ends of the porous layer. The results of this study provide stress concentration factors for porous coatings with sinter necks of known dimensions under loading conditions similar to those present along the lateral surface of a hip prosthesis.
Cellular interactions with biomaterials: In vivo cracking of pre‐stressed pellethane 2363‐80A
Authors: Zhao Q. , Agger M. P. , Fitzpatrick M. , Anderson J. M. , Hiltner A. , Stokes K. , Urbanski P. 
Published: December 2004

AbstractThe phenomenon of stress cracking of Pellethane 2363‐80A (PEU) was investigated using the cage implant system. A cytotoxic polyvinylchloride (PVC) and a silicone rubber containing an anti‐inflammatory steroid were used to create inflammatory environments in which the biostability of the pre‐stressed PEU was tested. These coimplants provided alternative in vivo environments to study in vivo polymer interactions. The inflammatory responses to the implanted cages were monitored by analyzing the exudates aspirated from the cages at different implantation times over 21 days. The pre‐stressed PEU specimens were retrieved after 5, 10, and 15 weeks postimplantation and examined by optical microscopy (OM) and scanning electron microscopy (SEM). The results support the conclusion that in vivo cracking of stressed (strained) Pellethane 80A is related to cell–polymer interactions. Severe cracking or rupture of the implanted PEU specimens was observed as early as 5 weeks postimplantation. Molecular chain degradation of the implanted specimens was evident from molecular weight measurements. Neither surface cracking nor degradation of macromolecules was found on the pre‐stressed PEU specimens with the added cytotoxic PVC implanted over 15 weeks. No cracking was observed on the pre‐stressed specimens in the presence of steroid silicone rubber, even after 10 weeks implantation.
Evaluation of metallic personalized hemiarthroplasty: A canine patellofemoral model
Authors: Laberge Martine , Dennis Bobyn J. , Drouin G. , Rivard Charles H. 
Published: December 2004

AbstractThe purpose of this study was to characterize the response of articular cartilage to weight bearing against a metallic personalized hemiarthroplasty prosthesis. Ten dogs each underwent surgery in which an elastomeric replica of the left femoral patellar groove was made. Using this replica, a 0.5‐mm‐thick prosthesis was cast in Co‐Cr alloy and subsequently the surface was polished to a mirror finish which had a center line average roughness value in the range of human hemiarthroplasty implants. A second surgery was performed to resurface the left trochlea with this prosthesis. Five animals were sacrificed at 3 months and 5 at 6 months. Cartilage damage occurred primarily in the distal region of the patella, and was especially evident at 6 months. Mechanical indentation tests conducted on patellar cartilage in a saline bath at 37°C indicated both increased deformation and residual deformation in the affected areas, indicative of degenerative change. Areas of fibrillation with a depletion of proteoglycans were identified histologically. These areas were only superficial at 3 months but became more extensive at 6 months. Rheological analysis of the synovial fluid of tests joints indicated that a decrease in viscosity occurred from 3 to 6 months, an additional indicator of progressive degeneration. This novel implant model showed that even if a metallic hemiarthroplasty implant had an identical geometry as the joint surface being replaced and had a reasonably smooth surface, cartilage degeneration inevitably resulted.
Evaluation of hydroxylapatite/poly(l‐lactide) composites: Mechanical behavior
Authors: Verheyen C. C. P. M. , De Wijn J. R. , Van Blitterswijk C. A. , De Groot K. 
Published: December 2004

AbstractBy mixing hydroxylapatite (HA) into L(‐) dilactide monomer, prior to polymerization to poly(L‐lactide) (PLLA), hydroxylapatite filled poly(L‐lactide) composites were obtained. This study reports about the mechanical properties of these composites compared with unfilled PLLA. It was concluded that a 30 wt% HA/PLLA composite has better compressive and tensile strengths, higher stiffness and Vickers hardness number than unfilled PLLA (Mv: 125‐150,000). Gas sterilization (ethylene oxide) affects molecular weight and flexural strength significantly. Implantation studies revealed loss of 50% of initial flexural strength within 3 weeks, and a faster decline of flexural strength was observed in phosphate buffered saline than in the subcutis of goats. From a mechanical point of view storage at −20°C proved to be a safe method. In its current state HA/PLLA composites can not be used as implant materials that have to resist major forces. However, such composites might be useful in nonloadbearing applications in orthopedic or maxillofacial surgery. © 1992 John Wiley & Sons, Inc.