摘要:

AbstractThe diffuse reflectance spectra of dental ceramic and composite resin specimens were analyzed by the Kubelka–Munk (K–M) theory of light scattering materials. This enabled the prediction of the spectra and color of differing thicknesses of these materials on various backgrounds, which were in good agreement with observation. The reflectance spectra of natural enamel and dentine sections were also measured on white and black backgrounds. This allowed the calculation of the K–M scattering (S) and absorption (K) parameters, which were compared with those of the restorative materials. The Chroma of these tooth sections increased slightly with the age of the patient, but the Hue and Value showed no systematic variation. Comparisons of the measured Munsell color for a range of composite resins and ceramics with that of the natural tooth sections showed that they generally exhibited a similar range of c

ISSN:0021-9304    

DOI:10.1002/jbm.820190502

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractMethods of assessing the biocompatibility of materials for use in medical devices were evaluated. Ten materials were tested using quantative, objectively gradedin vitrobiochemical and functional assays employing four cell lines (CCL 1, 74, 76, and 131) used in previous work and five primary cell types (human lymphocytes, polymorpho‐nuclear leukocytes, and mixed leukocytes, mouse macrophages, and mouse embryo). The biochemical methods (DNA synthesis, protein synthesis, and ATP activity) demonstrated good agreement in toxicity ranking of the materials, regardless of which cell culture was used and, also, the cell cultures responded similarly for each method. Methods that measured functional characteristics of cells (adhesion and phagocytosis) were highly sensitive but had low toxicity ranking agreement and reproducibility. Assays (defined as method and cell culture combinations) using cell lines were more reproducible than assays using primary cell types. Significant differences in sensitivity were noted among the assay systems for particular material types. Thein vitroassays were more sensitive to differences in material composition than was a 90‐day assay by subcutaneous implantation in r

ISSN:0021-9304    

DOI:10.1002/jbm.820190503

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractA method is described which is proposed to prolong the functional life of a Silastic finger joint endoprosthesis which has been shown to fail because of abrasion and cutting by the recipient bones. Swanson design Silastic finger joints prostheses were implanted into the knee joints of rabbits. The technique of simultaneously transplanting ear cartilage to the prosthetic implant bed was tested for the purpose of protecting the prostheses from wear and eventual failure. The clinical, radiographic, gross, and histologic results of the animals implanted for 1, 3, and 6 months show that the cartilage graft remains viable and it proliferates. The cartilage provides a smooth, gliding surface with normal appearing joint fluid surrounding the Silastic implant. Control limbs, with no cartilage grafts, had thinner, fibrous tissue encapsulating the implants. The presence of the cartilage reduced the amount of prosthetic wear particles observed in the tissue sections, thus indicating a protective function. The rabbit model developed an osteoarthritis that was caused by the prostheses in its knee joints and was unaffected by our cartilage grafting procedure. The success of our cartilage grafts, in the presence of such an arthritis, provides the impetus for its clinical use in arthritic human finger joints. Further studies are necessary to determine the clinical feasibility of a cartilage grafting technique and its efficacy in reducing implant failure in human finger joints.

ISSN:0021-9304    

DOI:10.1002/jbm.820190504

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractA thermoplastic polymer, Delrin 150 (polyoxymethylene homopolymer), with creep resistance ten times that of ultrahigh‐molecular‐weight polyethylene, is used as a material for total joint protheses. A study was made of the local and systemic host response to this polymer when implanted in three different mammalian species. 316 LC stainless steel was used as a control. The materials were implanted into muscle and bone as solid cylinders. A total of 446 samples were implanted into 74 animals. The duration of implantation ranged from 2 weeks to 2 years. A semiquantitative evaluation of local tissue reaction was performed. For each implant, 16 histological criteria were graded for severity of host tissue reaction. The liver, spleen, kidneys, pancreas, and lungs from each animal were also studied for evidence of systemic toxicity. The polymer implants exhibited a mild tissue reaction with the same characteristics as the control. Local tumor formation, bone osteolysis, and surrounding muscle necrosis were not seen. No pathological changes compatible with systemic toxicity by Delrin 150 were observed in the study of the organs. Delrin 150 in solid form did not exhibit local or systemic toxicity and is therefore biocompatible by this study. Powder implantation studies should be performed to simulate tissue response to wear partic

ISSN:0021-9304    

DOI:10.1002/jbm.820190505

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe biocompatibility of a type III casting gold alloy, an Ag‐Pd‐Cu‐Au‐based dental casting alloy and its two main structural components, a CuPd‐rich and an Ag‐rich phase, was studied after subcutaneous implantation for 7 weeks in 20 guinea pigs. The Ag‐Pd‐Cu‐Au alloy was surrounded by a capsule of immature collagen with fibroblasts and an increased vascular supply. The CuPd‐rich component induced and maintained an acute inflammation with highly vascularized granulation tissue. The tissue reaction to the Ag‐rich component and the Au‐based alloy was slight. Ten of the guinea pigs were sensitized to PdCl2prior to the implantation period, but this caused no enhanced tissue reaction, except for an increase in the number of mast cells aro

ISSN:0021-9304    

DOI:10.1002/jbm.820190506

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe cytoxicity and its correlation to alloy composition, structure, corrosion, as well as galvanic coupling was studied with 12 Ag‐Pd‐Cu‐type alloys, one conventional type III gold alloy and pure Ag, Cu, and Pd. The agar overlay cell culture technique was used. Single phase binary CuPd alloys were only slightly cytotoxic below a Cu content of 30 wt%. The tested multiphase alloys were all toxic, but no correlation between toxicity and Cu content could be observed. Solid solution annealing increased the cytotoxicity of a multiphase alloy. Exposure of a single phase alloy to an artificial saliva for 1 week prior to the test decreased its cytotoxicity significantly. Galvanic coupling of the alloys through an outer copper wire decreased their cytotox

ISSN:0021-9304    

DOI:10.1002/jbm.820190507

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractPorous coated surfaces for fixation of total hip replacement are a current trend in clinical orthopedics. Such devices are designed to be fixed by ingrowth of bony tissue, although in the absence of FDA approval for biologic fixation, fixation with PMMA cement is recommended by the implant manufacturers. In order to characterize the mechanical properties of the microinterlocked stem–cement interface, we tested both porous coated and smooth femoral components in cement mantles of consistent overall geometry. Under conditions of increasing load the smooth stems demonstrated stepwise irreversible subsidence into the mantle. Axial and circumferential strains measured in the cement containment vessels with the smooth stems showed that stepwise increases in tensile hoop strain occurred concomitantly with the stepwise incidents of stem subsidence. When subjected to the same loading conditions, the porous coated stems did not undergo stepwise incidents of subsidence, and hoop strain generation was reduced. In addition, a twofold increase in the failure load of the stem–cement interface was measured with the porous coated stems. Fatigue loading for 107loading cycles did not result in gross failure of either the microinterlocked or smooth interfaces. However, the data showed that during fatigue loading, stepwise subsidence of the smooth stems again occurred. The final subsidence magnitude of the smooth stem–cement interface at 107loading cycles was six times greater than the value associated with the porous coated stem. Thus the porous coating of femoral stems was shown to dramatically improve the load carrying capability and fatigue characteristics of the stem–cement in

ISSN:0021-9304    

DOI:10.1002/jbm.820190508

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe interaction of111Indium‐labeled platelets, and other blood components with the luminal surface of polydimethylsiloxane (PDMS) and low‐density polyethylene (LDPE) was determined using anex vivoarteriovenous shunt in the baboon. Both PDMS and LDPE showed little platelet accumulation at either high (200 cc/min) or low (25 cc/min) flow rates. PDMS accumulated more platelets at low than at high flow. When the surfaces of PDMS and LDPE were examined under scanning electron microscopy after 2.5 h of flow in the shunt circuit, red and white blood cells were attached. Platelets appeared to be confined to patchy areas covered by a fibrinlike network. The low platelet reactivity of LDPE and PDMS suggests their potential use as coatings for conventional, more platelet reactive, vascular graft materi

ISSN:0021-9304    

DOI:10.1002/jbm.820190509

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractA segmented polyurethane prosthetic anterior cruciate ligament prototype has been developed and itsin vivointegrity assessed in canine subjects. Prosthetic ligaments surgically implanted for 3, 4, 6, 8, 12, and 16 months were assessed clinically in living subjects, at time of autopsy, and microscopically postautopsy. It was found that the ligaments were adequate in strength to provide stability and last for periods up to 16 months. Notching of the ligaments was observed at two designated friction points.

ISSN:0021-9304    

DOI:10.1002/jbm.820190510

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

ISSN:0021-9304    

DOI:10.1002/jbm.820190511

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY