摘要:

AbstractThe authors describe a light and laser scanning microscopy study of hydroxyapatite‐coated titanium implants retrieved from humans. A histochemical technique, using von Kossa and basic fuchsin, allowed clear differentiation between mineralized bone and unmineralized bone matrix. The bone‐hydroxyapatite (HA) interface presented variable features: in some areas the mineralized bone was directly apposed to the HA surface, while in others an unmineralized red‐stained material, probably osteoid, was interposed. Laser scanning microscopy confirmed these findings showing a thin layer of fluorescent material at the interface. © 1994 John Wiley&Son

ISSN:0021-9304    

DOI:10.1002/jbm.820280502

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractHuman cancellous bone ingrowth studies were conducted on 19 consenting bilateral total knee arthroplasty (TKA) patients. Titanium porous coated cylinders were implanted into the medial femoral condyle of the contralateral knee during the first of two TKAs. Retrieval was performed at the time of the second TKA (6–131 weeks later), and fluorochrome analysis was conducted. Mean mineral apposition rates (MAR) at the interface measured 1.0 μm/day, whereas 4 mm away, the peripheral bone had a mean MAR of 0.8 μm/day. This represented a 25% acceleration in the interface bone remodeling rate when compared with the periphery (P<.05). This study showed the bone advanced appositionally at the interface at a rate of ≈ 1 μm/day. Analysis showed that when bone was over 50 μm from the porous coating, bone ingrowth did not occur. These results emphasize the need for surgical precision and careful postoperative management to achieve bone ingrowth. © 1994 John Wiley&S

ISSN:0021-9304    

DOI:10.1002/jbm.820280503

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractSynthetic biodegradable polymeric matrices, with a dense top layer and porous under‐layer, made of a (poly)ether/(poly)ester (PEO:PBT) copolymer called PolyactiveTM, and also of poly‐L‐lactide (PLLA), are under investigation as part of a cell‐seeded skin substitute for third‐degree, large‐scale skin defects. The biocompatibility of subcutaneously implanted matrices representing large body surface areas, were studied at 2, 4, 13, 26, and 52 weeks in rats. To investigate local or systemic effects, the weight development of the complete animal and of their hearts, kidneys, lungs, livers, and spleens, as well as the macroscopic and histologic appearance of the implants and organs, were monitored. Early inflammatory response was associated with surgical implantation trauma. All matrices showed neovascular and fibrous tissue ingrowth into the porous underlayer within 2–4 weeks after implantation. Copolymeric and PLLA matrices increasingly fragmented and liquified. After 1 year, small polymeric fragments embedded in fibrous, vascularized tissue could be retrieved at the implantation site. No systemic effects of the implants on the organs or on the animal as a whole were observed. These results and earlier studies on (skin) cell substrate properties and physicochemical characteristics of the matrices indicate the suitability of the matrices as part of a cell‐seeded skin substitute. © 1994 John

ISSN:0021-9304    

DOI:10.1002/jbm.820280504

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe osteogenic potential of demineralized bone matrix (DBM) has been demonstrated in multiple animal models and clinical applications. A particulate form of DBM is generally used to fill defects because it is easily packed into a defect site without operative planning or shaping. One potential disadvantage in the use of a particulate is the migration of particles from the defect site. To stem this, glycerol was added to DBM to improve handling properties. A study was undertaken to compare two forms of DBM with glycerol, with DBM particulate and autograft in a bony defect site. The model chosen consisted of bilateral 8‐mm trephine defects created in the parietal skull of 40 rabbits. Animals were sacrificed at 2 and 8 weeks. Results demonstrated both cartilage and bone induction with the three forms of DBM, with 75–90% of the linear width of the defect filled with new bone by 2 weeks. This was similar to the autograft (86%) and significantly greater than the unfilled defects (26%) at 2 weeks. The addition of glycerol to the DBM did not affect the inductive capacity, and produced a response similar to that of DBM particulate alone or autogenous bone. © 1994 John Wiley&Sons,

ISSN:0021-9304    

DOI:10.1002/jbm.820280505

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractA tensile test has been developed to test bioactive coating materials. Hydroxylapatite (HA) and fluorapatite (FA) coatings with various roughnesses were tested using sandblasted titanium (Ti) as a control material. Twelve goats received 7 implants each for 6 (2 goats), 12 (5), and 24 (4) week implantation periods. After 12 weeks the mean tensile strength values were highest for polished hydroxylapatite (HAP) followed by HA>FAP (polished fluorapatite)>FA>Ti, and hydroxylapatite type coatings were found to exhibit significantly higher values than fluorapatite type coatings or titanium implants. After 24 weeks no statistically significant differences could be found between any of the implant types. The order of the mean strength values was now HAP>HA>FA>FAP>Ti. Fracture always occurred between the coating and titanium if bone contact had been established. In conclusion, it is suggested that results from different types of test methods cannot be used to compare different types of bioactive coatings. © 1994 John Wiley&Sons, Inc

ISSN:0021-9304    

DOI:10.1002/jbm.820280506

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractRecent clinical studies have shown that the overall effectiveness of hemodialysis is determined by both the convective and diffusive transport of a wide range of different molecular weight solutes. In this study, transport data were obtained for vitamin B12and for polydisperse dextrans with a wide range of molecular weights using flat sheet Cuprophan and AN69 polyacrylonitrile membranes. The flux dependence of the actual sieving coefficient was described using classical membrane transport theory, allowing accurate measurements of both the diffusive and convective contributions to the overall solute transport through the porous structure of these dialysis membranes. Asymptotic membrane sieving coefficients and hindered diffusivities were in good agreement with a hydrodynamic model that accounts for the membrane pore size distribution through an expression for the solute partition coefficient in a random porous medium. This model provides an accurate quantitative description of both solute diffusion and convection through hemodialysis membranes, which is critical for the effective design and operation of hemodialyzers. © 1994 John Wiley&Sons, Inc

ISSN:0021-9304    

DOI:10.1002/jbm.820280507

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe carcinogenicity and chronic toxicity of 316L stainless steel, nickel, Ti‐6Al‐4V, hydroxyapatite (HA)‐coated Ti‐6Al‐4V, aluminum oxide containing yttrium oxide were evaluated by implanting solid rods of each material in the thigh muscle of C57BL/6N mice for 24 months. Nickel alloy showed high carcinogenic and toxic potencies, whereas other materials showed no evidence of them. Tumors retaining nickel alloys were malignant fibrous histiocytoma or fibrosarcoma. In some cases, lymphomata that seemed to develop spontaneously were found around the implants because lymphocytes were known to accumulate in chronic inflammatory lesions, and this phenomenon also might be applied to lymphoma. © 1994 John Wiley

ISSN:0021-9304    

DOI:10.1002/jbm.820280508

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractHigh molecular weight poly(vinyl chloride) and aliphatic polyurethane (Tecoflex)‐based ion selective membranes, with normal and reduced amounts of plasticizer, as well as without plasticizer, were tested with respect to their analytical properties, their biocompatibility, and cellular responses. The analytical properties of the membranes did not change significantly within a wide range of polymer to plasticizer rations. However, the membranes with reduced plasticizer content had better adhesive properties, less anion interference, extended life time, and better biocompatibility. Using the cage implant system, the results showed that an increase of plasticizer weight percent in Tecoflex membranes correlated positively with the increase in host inflammatory response up to 14 days of implantation. The results also demonstrated that both PVC and Tecoflex‐based ion‐selective membranes with the most common membrane composition (1:2 polymer to plasticizer ratio) exhibited a similar acute inflammatory response, but the PVC‐based membrane elicited a reduced chronic inflammatory response when compared with the Tecoflex‐based membrane. © 1994 John Wiley

ISSN:0021-9304    

DOI:10.1002/jbm.820280509

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractLeucite is a major crystalline component of dental porcelains. The presence of tetragonal leucite in dental porcelains increases their coefficients of thermal expansion due to its high coefficient of thermal expansion (20–25 × 10−6/°C). This is particularly useful for those porcelains designed for bonding to precious metals and nickel alloys. The purpose of this study was to determine the leucite content of selected commercial dental porcelains in relation to their coefficient of thermal expansion values. The weight fraction of leucite was determined with quantitative x‐ray diffraction using copper as an internal standard. Coefficient of thermal expansion values were determined using a thermal dilatometric analyzer. Five commercial body porcelains were studied. Leucite was not detected in samples of Vitadur N and Duceram LFC. An ANOVA showed that there was a significant difference in the weight fraction of leucite for Silhouette, Ceramco II, and Optec HSP porcelains. Linear regression revealed a correlation (R= 0.91) between weight fraction of leucite and the coefficient of thermal expansion for those samples containing leucite. Ducram LFC, which is recommended by the manufacturer for use with metals and leucite‐containing porcelains, had no detectable leucite although the coefficient of thermal expansion was found to be 13.2 ± 0.4 × 10−6/°C at 25–472°C. A low glass transition temperature contributed to the high average coefficient of thermal expansion value. © 1994 Jo

ISSN:0021-9304    

DOI:10.1002/jbm.820280510

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractBovine pericardial tissue was stabilized through a dyemediated photooxidation reaction. Shrink temperature analysis of the stabilized tissue indicated a material with similar properties to untreated pericardial tissue and unlike identical tissue treated with glutaraldehyde. Photooxidized tissue was resistant to extraction when compared with untreated tissue or control tissue treated in the absence of light or dye. Photooxidized tissue was also resistant to enzymatic digestion by pepsin and to chemical digestion by cyanogen bromide (CNBr). In contrast, untreated or control treated tissues were readily digested by these reagents. Reduction of photooxidized tissue with β‐mercaptoethanol prior to CNBr digestion partially restored susceptibility of the tissue to CNBr digestion, indicating the photooxidation of methionine residues. Soluble collagen derived from bovine pericardium was used as a model compound for the photooxidation reaction. Polyacrylamide gel electrophoresis analysis indicated the photooxidative conversion of collagen into higher molecular weight aggregates consistent with intermolecular crosslink formation. Photooxidized tissue was stable toin vivodegradation when compared with control tissue. Results presented here indicate a crosslinked pericardial tissue produced by dye‐mediated photooxidation possessing properties of chemical stability, enzymatic stability,in vivostability, and biomechanical integrity suitable for use as a biomaterial. © 1994 John Wiley&Sons

ISSN:0021-9304    

DOI:10.1002/jbm.820280511

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY