摘要:

AbstractThis study was conducted to investigate some fundamental fatigue testing variables as they apply to the response characteristics of acrylic bone cement. Cyclic loading under load control was conducted at frequencies of 1, 2, 5, 10, and 20 Hz in air at room temperature. At a tensile stress range of 0.3–20.0 MPa the fatigue life increased linearly with logarithmic frequency. The effect of conditioning and testing in saline at both room temperature and 37°C at similar stress levels and a frequency of 10 Hz were also examined. When compared to dry testing at room temperature, testing in saline at 37°C resulted in a reduction in fatigue life while testing in saline at room temperature produced an increase in fatigue life. Of a number of statistical distributions considered, the Weibull was found to be the most appropriate in documenting the findings of this investigation. A companion fractographic investigation of the failure surfaces demonstrated distinct regions of crack growth and fast fract

ISSN:0021-9304    

DOI:10.1002/jbm.820230802

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe effect of gamma irradiation on the physicochemical properties of injectable human amninon collagen was investigated. Pepsin‐extracted human amnion collagen was purified, reconstituted, and irradiated with varying doses of gamma irradiation (0.25 Mrads to 2.5 Mrads). Gamma irradiation had a significant impact on the physical characteristics of the collagen. The neutral solubility of collagen in PBS at 45°C was decreased from 100% for the nonirradiated control sample to 16% for the 2.5 Mrads irradiated sample. SDS polyacrylamide gel electrophoresis also demonstrated the dose‐dependent effect of gamma irradiation on collagen crosslinks. Electron microscopic observation revealed that even at low irradiation dose (0.25 Mrads), collagen fibril diameter increased. The average diameter was 50 nm for nonirradiated control fibrils, while 4.4% percent of the irradiated collagen fibrils had a diameter greater than 100 nm. Irradiated collagen showed little evidence of damage. Well‐preserved cross‐strations were found in collagen fibrils at all doses of irradiation. Native amnion collagen irradiated with gamma rays demonstrated a slight increase in resistance to collagenase degradation compared with nonirradiated native collagen samples. Increased resistance to collagenase did not correlate with increasing irradiation dose. After 30 min of incubation at 37°C, both irradiated and non‐irradiated collagen was completely digested by collagenase. However, gamma‐irradiated collagen did become more sensitive to hydrolysis by trypsin. The higher the irradiation doses used, the greater sensitivity to trypsin was observed. At 0.25 Mrads irrdiation only a slight increase was found. No marked differences in amino acid composition were noted among the high dose irradiated, low dose irradiated and control am

ISSN:0021-9304    

DOI:10.1002/jbm.820230803

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractA study was conducted to determine the ability of hamsters to eliminate in the urine, or store in the organs, large quantities of metal salts given over a period of several months. In addition, the effect of prior immunization on metal ion clearance was determined. The results indicated that nickel was rapidly eliminated in the urine and that the level in the organs was similar to that of control animals. Cobalt was eliminated more slowly than was nickel. The organ levels of cobalt were similar to those of control animals with a slight elevation in the liver of the injected animals. Chromium was eliminated in the urine very slowly, was red cell associated, and the levels were elevated in all the organs (liver, lung, spleen, kidney) compared to control. Prior immunization with metal salts increased the storage of chromium.

ISSN:0021-9304    

DOI:10.1002/jbm.820230804

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractA poly‐ether‐urea‐urethane was synthesized by copolymerization of 4,4′‐diphenylmethanediisocyanate (MDI), propanediamine, and poly‐oxytetra‐methylene glycol (M.W. 1000). Two other corresponding copolymers were also synthesized by adding amino terminated poly‐amidoamine macromonomers, purposely synthesized, so as to insert relatively small amounts (6 and 15 weight %) of two types of poly‐amidoamine segments in the final product. Of the three copolymers several physicochemical and mechanical properties have been determined, and their heparin adsorption ability, blood compatibility, and cytot

ISSN:0021-9304    

DOI:10.1002/jbm.820230805

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractSpecially prepared biphasic calcium phosphate (BCP) macroporous ceramics consisting of an intimate association of beta tricalcium phosphate (b̃‐TCP) and hydroxyapatite (HA) with b̃‐TCP/HA weight ratios of 15/85, 35/65, and 85/15 were implanted in surgically created periodontal osseous defects in dogs and recovered after 6 months. A decrease in average size of crystals in BCP ceramics and an increase in the size of microporosities in the surface and at the core of the ceramic after implantation were observed, indicating thatin vivodissolution has taken place. The resorbability (reflectingin vivodissolution) of BCP ceramics depended on their b̃‐TCP/HA ratios, the higher the ratio, the greater the resorbability. The formation of microcrystals with crystallographic properties and Ca/P ratio similar to those of bone apatite crystals were also observed. The abundance of these crystals were directly related to the b̃‐TCP/HA ratio of the BCP ceramic before implantation. The formation of the bone apatite‐like crystals may be due to the precipitation of calcium and phosphate ions released from the dissolving ceramic crystals (the b̃‐TCP component dissolving preferentially to the HA component). Results from this study suggested that one of the means of controlling resorbability (in vivodissolution) of BCP ceramic is by varying its

ISSN:0021-9304    

DOI:10.1002/jbm.820230806

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

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

ISSN:0021-9304    

DOI:10.1002/jbm.820230807

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractBiomedical polymers used in constructing implantable artificial devices may affect host responses to the material and ultimately contribute to the success or failure of a device via mechanisms of cell–polymer interactions. Human peripheral blood monocytes (MO) cultured in the presence of several such biomedical polymers released factors that stimulated fibroblast proliferation and/or collagen synthesis. The factors that stimulated fibroblast proliferation were differentially released from monocytes cultured in the presence of Dacron, polyethylene, expanded polytetrafluoroethylene (ePTFE), polydimethylsiloxane, and polystyrene (control). Supernatants obtained from monocytes cultured in the presence of Biomer, a segmented polyetherurethane, were unable to stimulate fibroblast proliferation. However, supernatants from all cultures, including MO‐Biomer cultures, were able to induce collagen production from the same target fibroblasts. These same supernatants also were shown to contain interleukin 1 (IL1) activity. Neutralization of the fibroblast stimulatory potential (FSP) activity with antibodies directed against human IL1 and human PDGF demonstrated that IL1 and not PDGF was responsible for the FSP activity. Results of this study show that by affecting macrophage activation, different biomedical polymers can affect host biocompatibility responses by altering fibroblast proliferation and funct

ISSN:0021-9304    

DOI:10.1002/jbm.820230808

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractAqueous suspensions of glutaraldehyde cross‐linked fibrillar collagen and non‐cross‐linked fibrillar collagen were examined by rheometry, particle size analysis, and microscopic techniques. Although cross‐linked collagen suspensions were similar to non‐cross‐linked suspensions by microscopic and size analyses, they differed in rheometric properties. Concentric cylinder Couette flow, shear creep, uniaxial creep, and porous bed flow all revealed that cross‐linked collagen was more resistant to deformation and flow than non‐cross‐linked collagen. These results were in agreement within vivodermal implantation studies, both in pig and human; i.e., compared to non‐cross‐linked collagen, the cross‐linked formulation was more difficult to inject into tissue and did not spread uniformly, sometimes giving rise to palpable lumps or large masses evident in histological sections. When hyaluronic acid was blended with cross‐linked collagen to achieve a final hyaluronate concentration of 5 mg/mL, there was a significant improvement in ease of injection into tissue. Rheometry on blends of hyaluronate and cross‐linked collagen demonstrated that the blend required lower forces to achieve deformation and flow, compared to cross‐linked collagen alone. Particle size analysis on the blend showed a reduction in fiber aggregate dimensions, compared

ISSN:0021-9304    

DOI:10.1002/jbm.820230809

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThere are no differences in the multinucleate cell formation in normal and athymic mice after the subcutaneous implantation of a cellophane strip. The number of Ia+epitheloid cells and multinucleate foreign body giant cells was lower and the number of epitheloid cells sharing the marker of activated macrophages (M 57) was higher in athymic compared to normal mice. The epitheloid cells of athymic and euthymic animals exhibited no difference in the expression of Mac‐2 molecule. The difference of the expression of surface markers between athymic and euthymic animals does not influence the foreign body giant cell formatio

ISSN:0021-9304    

DOI:10.1002/jbm.820230810

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

ISSN:0021-9304    

DOI:10.1002/jbm.820230811

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY