Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Polyethylene”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 379 records · Page 21Linked to original sources
PubMed1976

[The change of physical properties of plastics (polyoxymethylenecopolymer, polyethyleneterephthalate, polyethylene, polytetrafluorethylene) after animal implantation and autoclavation (author's transl)].

The change of physical properties of plastics (polyoxymethylene-copolymer, polyethyleneterephthalate, polyethylene, polytetrafluorethylene) and the bio-compatibility of these materials were examined by implantation in the backmuscle of 6-month-old male rabbits for 4 and 12 weeks and after autoclavation. We have found out, that after implantation and autoclavation polyethylene-terephthalate demonstrates a strong diminution of the visco-elastic qualities. Polyethylene and polytetrafluorethylene were not changed by these treatments. After an implantation of 12 weeks and an autoclavation of four times the visco-elastic properties of polyoxymethylene-copolymer were only slightly diminished by 10 to 15%. The histological investigation of the surrounding tissue demonstrated a very good bio-compatibility of polyethylene. After an implantation of 4 weeks polyoxymethylene-copolymer, polyethyleneterephthalate and polytetrafluorethylene produced a comparable foreign body reaction, which, however, was evidently diminished after an implantation of 12 weeks.

Animals↗
PubMed2003

Flexural strength of composites: influences of polyethylene fiber reinforcement and type of composite.

MAIN PROBLEM: The microfill veneering of hybrid composite restorations has been indicated to improve esthetics. Also, polyethylene fiber reinforcement has been proposed for use in composite restorations in high-stress clinical situations. However, minimal information in the literature addresses the influence of such combinations on the resistance to fracture. The purpose of this study was to investigate the flexural strength of two composites, a microfill and a hybrid, the effect of their combination, and the influence of polyethylene fiber reinforcement. MATERIALS AND METHODS: Twenty-eight specimens were prepared using a standard metallic mold (20x2x2 mm) and divided into groups of seven each: Filtek Z-250 (3M ESPE, St. Paul, Minn., USA) (group I), Filtek A-110 (3M ESPE) (group II), Filtek Z-250 combined with Filtek A-110 (group III), and Filtek Z-250 combined with polyethylene fiber (Ribbond, Seattle, Wash., USA) (group IV). The specimens were stress-loaded to fracture in a three-point bending device according to International Standardization Organization (ISO) 4049. RESULTS: Data were analyzed using analysis of variance and Tukey's test at a 0.05 level of significance. No statistically significant differences were observed between groups I and IV. Group II, however, exhibited statistically lower resistance to fracture than the other groups. Group III presented intermediate results, showing statistically higher fracture resistance than group II but lower than group I. CONCLUSIONS: With the methodology employed, microfill composite presented the lowest flexural strength, but its association with hybrid composite increased the resistance to fracture. The combination of polyethylene fiber and hybrid composite did not present higher flexural strength than hybrid composite alone.

Analysis of Variance↗
PubMed2005

Long-term outcomes of ultra-thin porous polyethylene implants used for reconstruction of orbital floor defects.

PURPOSE: The objective of this article is to present the long-term outcomes of ultra-thin polyethylene implants used for orbital floor reconstruction in facial trauma patients. MATERIALS AND METHODS: From 1998 to 2004, 38 patients underwent orbital floor reconstruction with porous polyethylene implants with a mean follow-up of 4 years. A subciliary incision and preexisting facial wounds or scars were used. The boundaries of the maxillofacial injury and the orbital volumes of both orbits were assessed by computed tomography images obtained pre- and postoperatively. In all patients, ultra-thin porous polyethylene implants in various sizes were used to reconstruct the orbital floor defect. RESULTS: None of the patients needed removal of the implants during the follow-up. The volume increase of the traumatized orbits ranged from 0.04 to 6.18 (average 3.12 +/- 1.48) mL compared with the intact orbit (P < 0.01). This difference was not significant postoperatively (P > 0.01). Postoperative ectropion in three cases was corrected under local anesthesia. Persistence of complications were as follows: enophthalmos, 3 in 28; diplopia, 1 in 16; dystopia, 1 in 4; and infraorbital nerve hypoesthesia, 3 in 31. One patient underwent late enucleation of the globe because of initial penetrating trauma. CONCLUSIONS: We recommend the use of ultra-thin porous polyethylene implants in the reconstruction of the orbital floor defects in facial trauma patients. The implants are durable in the long-term and mimic the anatomy of the thin orbital floor and avoid the morbidity of autogenous bone grafts.

Adult↗
PubMed2004

[Mechanical property analysis of polyethylene fiber reinforced polymethyl methacylate].

OBJECTIVE: To investigate if the Ribbond polyethylene fiber has the effect of reinforcing polymethyl methacylate. METHODS: 28 specimens were fabricated and divided into 3 groups: group of chemical-cured PMMA, group of chemical-cured PMMA reinforced by stainless steel wire and group of chemical-cured PMMA reinforced by Ribbond polyethylene fiber. A three-point bending test was used to measure the flexural strength and flexural modulus of specimens. Then the data were analyzed with a one-way analysis of variance. RESULTS: The flexural strength of chemical-cured PMMA group was (51.383 +/- 2.761) MPa, the flexural modulus was (1791.2 +/- 113.760) MPa; The flexural strength of stainless steel wire reinforced group was (58.725 +/- 1.218) MPa, the flexural modulus was (2092.76 +/- 120.28) MPa; The flexural strength of Ribbond polyethylene fiber reinforced group was (80.975 +/- 2.58) MPa, the flexural modulus was (2866.53 +/- 107.51) MPa. The one-way analysis of variance showed that the results were significant (P < 0.001). Newman-Keuls method showed that the differences among all groups were significant (P < 0.05). CONCLUSION: The Ribbond polyethylene fiber can raise the flexural strength and flexural modulu of polymethyl methacylate.

Dental Bonding↗
PubMed1990

Long-term evaluation of a new selectively biodegradable vascular graft coated with polyethylene oxide-polylactic acid for right ventricular conduit. An experimental study.

Low-porosity woven Dacron grafts have been used extensively as an extracardiac conduit in the surgical treatment of congenital and acquired heart diseases involving total heparinization. Caution is still warranted in their use, however, because of long-term complications, including calcification and development of obstructive fibrous peel. In contrast, high-porosity grafts offer much better tissue anchorage and healing but cannot be used under heparinization. We have developed a compound vascular prosthesis in which a knitted Dacron graft is coated with a polymeric biodegradable sealant. Polyethylene oxide-polylactic acid-segmented copolymers comprised the degradable component of the graft. In vitro studies showed that the coated prosthesis exhibited a highly flexible elastomer-like mechanical response. The prostheses were completely watertight, and significant degradation started after 1 week, with absorption completed after 3 weeks. Seven woven and six knitted polyethylene oxide-polylactic acid-coated Dacron grafts used as extracordiac conduits (16 mm), connecting the right ventricle and the pulmonary artery were implanted in dogs. The dogs were killed after 12 to 18 months, and the results are reported. Scanning electron microscopy examination showed peel detachment and nonhomogenous intimal surface with fenestrations in the woven graft group, but complete healing and incorporation of the pseudointima with homogenous, thin lining of the luminal surface in the polyethylene oxide-polylactic acid-coated group. Histologic studies indicated much superior healing and anchorage of the periprosthetic tissue and the pseudointima in the polyethylene oxide-polylactic acid-coated grafts. The biodegradable polymer was fully degraded and exhibited a complete incorporation of the compound vascular prosthesis. This study indicates the superior healing properties of these selectively biodegradable grafts, which might increase long-term patency and decrease complications of right ventricular conduits.

Animals↗
PubMedDate not supplied

Modulation of tissue ingrowth into porous high-density polyethylene implants with basic fibroblast growth factor and autologous blood clot.

OBJECTIVE: To investigate the effect of direct application of biologic materials normally present in wounds (basic fibroblast growth factor [bFGF] and autologous blood clot [ABC]) to accelerate the bony and soft tissue ingrowth into porous high-density polyethylene implants. METHODS: We conducted a prospective, blinded animal histological study. Disks made of porous high-density polyethylene impregnated with bFGF or ABC were implanted into adult Sprague-Dawley rats in both subcutaneous and subperiosteal locations. Animals were killed and implants were harvested at 2, 4, and 10 weeks postimplantation and examined histologically for fibroblast invasion, collagen deposition, and inflammatory reaction.The results were compared with control (untreated) implants. RESULTS: As a group, the histological results showed significantly more fibroblasts within the ABC-treated implants than control implants or bFGF-treated implants. This difference in the number of fibroblasts between ABC-treated implants and bFGF-treated and control implants was also statistically significant 2 weeks after implantation. CONCLUSIONS: At the concentration of bFGF of 1 microg/10 microL, no acceleration of tissue ingrowth into porous high-density polyethylene implants was noted. However, when porous high-density polyethylene implants were treated with ABC, the implants were invaded to a greater degree by soft tissue, particularly in the early postoperative period (first 2 weeks). Bioactive substances associated with the coagulation and platelet cascades present in the ABC may be responsible for this accelerated incorporation of the porous implant and may have clinical implications. Arch Facial Plast Surg. 2000;2:27-33

Animals↗
PubMedDate not supplied

Cleft lip nasal reconstruction using porous high-density polyethylene.

BACKGROUND: The multitude of factors involved with a unilateral cleft lip nasal defect has spurred various surgical techniques in the past. Recently, synthetic materials have been introduced for use in nasal reconstruction. OBJECTIVE: To report on and illustrate the use of porous high-density polyethylene implants in cleft lip nasal reconstruction. DESIGN: A retrospective review of cleft lip nasal reconstruction using porous high-density polyethylene in patients with a unilateral cleft lip defect from January 1, 1993, through June 30, 2000. SETTING: Facial plastic surgery private practice. PATIENTS: Eighteen patients with a unilateral cleft lip without a history of formal rhinoplasty. INTERVENTIONS: All 18 patients required multiple implants, including a columellar strut, premaxillary and prealveolar plumper grafts, a dorsal tip implant, and a unilateral nasal valve batten, using the open rhinoplasty approach. RESULTS: Favorable aesthetic results, as judged by one of us (T.R.), were achieved in all patients. All implants were well tolerated. Postoperative follow-up ranged from 6 months to 7 years. A complication occurred in 1 patient (6%), which resolved with removal of a single implant and intravenous antibiotic therapy. No other complications, including skin erosion or implant extrusion, have been noted. CONCLUSIONS: Porous high-density polyethylene implants for cleft lip nasal reconstruction are well tolerated and achieve good aesthetic results. Porous high-density polyethylene implants lend stability through fibrovascular ingrowth, with integration of the implants to the surrounding tissue.

Cleft Lip↗
PubMed1976

An evaluation of bone growth into porous high density polyethylene.

The purpose of this investigation was to study bone growth into porous polyethylene rods as a function of time and pore structure. Previous studies have indicated the biocompatibility of solid polyethylene materials which are currently being used clinically. Porous polyethylene rods were implanted in the femurs of mongrel dogs which are sacrificed four, eight, and 16 weeks postoperatively. The implants were then sectioned and examined histologically and microadiographically. Quantitative techniques were employed to determine the amount of bone ingrowth as a function of time and pore size. The pore structures of the materials were evaluated using optical microscopy and mercury intrusion porosimetry. The results of this investigation have demonstrated that porous polyethylene is capable of accepting bone growth into pores as small as 40 mum. The optimum rate of bone ingrowth was observed in pore sizes of approximately 100 to 135 mum, with no increase in the rate of bone ingrowth observed in samples possessing larger pore sizes. No adverse tissue response was found at implant times up to 16 weeks in pore sizes of 100 mum or larger.

Biocompatible Materials↗
PubMed1978

Wear characteristics of UHMW polyethylene: a method for accurately measuring extremely low wear rates.

The wear of UHMW polyethylene bearing against 316 stainless steel or cobalt chrome alloy was measured using a 12-channel wear tester especially developed for the evaluation of candidate materials for prosthetic joints. The coefficient of friction and wear rate was determined as a function of lubricant, contact stress, and metallic surface roughness in tests lasting two to three million cycles, the equivalent of several years' use of a prosthesis. Wear was determined from the weight loss of the polyethylene specimens corrected for the effect of fluid absorption. The friction and wear processes in blood serum differed markedly from those in saline solution or distilled water. Only serum lubrication produced wear surfaces resembling those observed on removed prostheses. The experimental method provided a very accurate reproducible measurement of polyethylene wear. The long-term wear rates were proportional to load and sliding distance and were much lower than expected from previously published data. Although the polyethylene wear rate increased with increasing surface roughness, wear was not severe except with very coarse metal surfaces. The data obtained in these studies forms a basis for the subsequent comparative evaluation of potentially superior materials for prosthetic joints.

Absorption↗
PubMed1983

Fracture of porous polyethylene-bone composite.

Porous high-density polyethylene specimens were implanted in the femurs of mongrel canines. At the end of the residency period (3 or 6 months), the animals were sacrificed and the implants were retrieved. The work-of-fracture of the implant specimens was then determined using the technique of Tattersall and Tappin. The work required to fracture a specimen in three-point bending by controlled crack propagation through a triangular cross section was obtained directly from the load-deflection curve. The area of the resulting fracture surface was measured by macrophotographic techniques, and the work-of-fracture was calculated as work per unit area. The implants were subsequently sectioned and examined microradiographically to determine the extent of bone ingrowth. Bone specimens adjacent to the implants and porous high-density polyethylene controls (no ingrowth) were also tested to determine their work-of-fracture. The results showed that bone adjacent to the implant specimens had a higher work-of-fracture than normal medial, canine femoral bone and was not appreciably different from the composite. The work-of-fracture of porous high-density polyethylene was not significantly increased by an increase in bone infiltration, and this anomalous behavior was attributed to a degradation of the polyethylene during implant residence. Control studies supported this hypothesis.

Animals↗
PubMed1992

Interactions of thermally denatured fibrinogen on polyethylene with plasma proteins and platelets.

During the investigation of fibrin deposition onto hydrophobic polymers in contact with human blood, a model was developed in which fibrinogen was denatured and irreversibly coated onto a polyethylene surface by heating to 70 degrees C for 10 min. The denatured fibrinogen-polyethylene surface is resistant to fluid wall shear rates of up to 550 s-1 and the fibrinogen does not desorb in the presence of plasma proteins. Compared to uncoated polyethylene, little albumin or fibrinogen adsorbs to heat-denatured fibrinogen. Thrombin binds to the denatured fibrinogen-coated polyethylene with low affinity and also acts on the surface-bound denatured fibrinogen and cleaves fibrinopeptide A (FPA) quantitatively. Washed, 51Cr-labeled platelets do not adhere to the thermally denatured fibrinogen at either low or high shear rates compared to surfaces coated with undenatured fibrinogen (p < 0.01). These observations support the role of the D domain of fibrinogen in platelet adhesion because this is the region that is denatured by heating. In contrast, the E domain of fibrinogen is not altered by heating to 70 degrees C and hence remains susceptible to thrombin and/or plasmin cleavage. The characteristics of this surface are such that it can be used to develop fibrin-coated surfaces for use in studies of thrombus formation on artificial surfaces.

Absorption↗
PubMed1993

Competitive adsorption of albumin against collagen at solution-air and solution-polyethylene interfaces.

The adsorption of human serum albumin (HSA) from the binary mixtures with collagen was monitored at solution-air and solution-polyethylene interfaces by the in situ measurements. The results clearly demonstrate that on both interfaces albumin is the only adsorbing protein within a large collagen solution concentration range. At the albumin concentration equal to 0.005 mg/mL, the presence of collagen in solution results in the enhancement of albumin adsorption at solution-air interface relative to its adsorption from the single protein system. The same phenomenon is manifested at the solution-polyethylene interface, although the increase in albumin adsorption at this interface occurs at the albumin concentration equal to 0.01 mg/mL. These results are attributed to the lowering in the solution-air and solution-polyethylene interfacial tensions, and thus to the increase in the spreading characteristics of albumin in the presence of collagen molecules. The desorption experiments carried out with a buffer solution on polyethylene surfaces reveal the irreversibility of adsorbed albumin from both the single and the binary mixtures with collagen. When after 20 h of adsorption from the solutions containing albumin only, collagen was added to these solutions or when the samples after that period of time were first rinsed with a buffer and then with a collagen solution, the amounts of albumin remaining at the surfaces were in both cases reduced by one-half.

Adsorption↗
PubMed1993

Platelet-mediated adhesion of Staphylococcus epidermidis to hydrophobic NHLBI reference polyethylene.

The effects of platelets and plasma proteins on the adhesion of Staphylococcus epidermidis strain RP62A to hydrophobic NHLBI reference polyethylene was quantitatively studied using a rotating disk system to generate well-defined shear conditions simulating the hemodynamics of human blood circulation. Bacterial adhesion was quantified by adhesive coefficient, the percentage of bacteria transported to the surface that becomes adherent. The results showed that surface modification by adsorption of plasma proteins reduced the adhesion of S epidermidis as compared to the bare polymer surface. This surface modification was not sufficient to eliminate completely bacterial adhesion, even at the highest physiologic shear stress level. S epidermidis did adhere strongly to polyethylene surface modified by platelets. This is readily evident as approximately 50% of the adherent S epidermidis were bound to contact-activated platelets which occupied only 4% of the surface area. Adhesive coefficients to platelets were significantly greater than to the protein-adsorbed polyethylene surface by at least one order of magnitude (P < or = .01) across the range of physiological shear conditions investigated. These studies show that it is biologic surface modification by contact-activated platelets, and not plasma proteins, which mediates S epidermidis adhesion to polyethylene.

Bacterial Adhesion↗
PubMed1993

Metal ion concentrations in retrieved polyethylene total hip inserts and implications for artifactually high readings in tissue.

Although there are many studies which document high metal ion concentrations in clinically retrieved tissues surrounding total joint replacements, most investigations have remained cautious in their interpretation due to the artifactual influences of metal particulate. The possible contribution of polyethylene wear debris to artifactually high periprosthetic metal ion concentration readings has not been previously considered. This study documents the potential role of polyethylene particulate contamination in causing artifactually high metal concentration readings in tissues. The data showed metal ion contamination in the polyethylene was progressive at each stage of exposure to metal: from bar stock preparation, to manufacturing, to in vivo ambulation. The manufacturing and machining processes showed a statistically significant (P < or = .05) increase in metal ion concentrations in the nonarticulated acetabular inserts over bar stock. The results of this study demonstrate that periprosthetic tissue and synovial fluid metal ion concentration data must be interpreted with caution due to possible artifactual problems associated with metal ion contaminated polyethylene particulate.

Alloys↗
PubMed1994

Fatigue crack propagation behavior of ultra high molecular weight polyethylene under mixed mode conditions.

Analytical studies of the stresses on and within ultra high molecular weight polyethylene joint components suggest that damage modes associated with polyethylene fatigue failure are caused by a combination of surface and subsurface crack propagation. Fatigue crack propagation tests under mixed mode loading conditions were conducted on center-cracked tension specimens machined from extruded blocks of sterilized polyethylene in an attempt to determine how fatigue cracks change direction in this material. Cyclic testing was performed using a sinusoidal wave form at a frequency of 5 Hz and an R-ratio (minimum load/maximum load) of 0.15. Specimens had the notch oriented perpendicular to the direction of applied load and at angles of 60 degrees and 45 degrees to the loading direction. Numerical analyses were used to interpret the experimental test and to predict the fatigue behavior of polyethylene under mixed mode conditions. It was found that all cracks eventually propagated horizontally, regardless of the initial angle of inclination of the notch to the direction of applied cyclic load. In fact, the extent of the curvilinear crack growth was quite limited. An effective range of cyclic stress intensity factor was calculated for correlation with the rate of crack growth. The results followed a Paris relation, with crack growth rate linearly related to a power of the range of stress intensity, for all three crack orientations. The numerical analyses adequately modeled the experimental fatigue crack growth results.

Materials Testing↗
PubMed2003

Modulation of bone ingrowth and tissue differentiation by local infusion of interleukin-10 in the presence of ultra-high molecular weight polyethylene (UHMWPE) wear particles.

Interleukin-10 (IL-10) is a cytokine that plays a major role in suppressing the inflammatory response, particularly cell-mediated immunity that is characteristic of the TH1 response. The purpose of this study was to determine whether local infusion of IL-10 could mitigate the suppression of bone ingrowth associated with polyethylene wear particles. Drug test chambers were implanted in the proximal tibia of 20 mature New Zealand White rabbits. The DTC provided a continuous 1 x 1 x 5-mm canal for tissue ingrowth. After a 6-week period for osseointegration, the DTC was then connected to an osmotic diffusion pump. IL-10 at doses of 0.1-100 ng/mL (0.25 microL/h) was infused with or without ultra-high molecular weight polyethylene particles (0.5 +/- 0.2 microm diameter, 10(12) particles/mL) present in the chamber for a 3- or 6-week period. The tissue in the chamber was harvested after each treatment; sections were stained with hematoxylin and eosin for morphometric analysis. Osteoclast-like cells were identified by immunohistochemical staining using a monoclonal antibody directed against the alpha chain of the vitronectin receptor, CD51. Osteoblasts were identified using alkaline phosphatase staining. In dose-response studies, infusion of 1 ng/mL IL-10 yielded the greatest bone ingrowth in the presence of particles. The addition of polyethylene particles evoked a marked foreign body reaction and fibrosis; bone ingrowth was significantly suppressed (p = 0.0003). Bone ingrowth was increased by over 48% with infusion of IL-10 for the final 3 weeks of a 6-week ultra-high molecular weight polyethylene particle exposure compared with particles alone (p = 0.027). IL-10 is a cytokine that plays a major role in suppressing the inflammatory response, especially cell-mediated immunity that is characteristic of the TH1 response. Local infusion of immune-modulating cytokines such as IL-10 may prove to be useful in abating particle-induced periprosthetic osteolysis.

Alkaline Phosphatase↗
PubMed2004

Characteristics of polyethylene wear particles isolated from synovial fluid after mobile-bearing and posterior-stabilized total knee arthroplasties.

The size, shape, and number of polyethylene wear particles found in synovial fluids of patients 1 year after implantation of 22 well-functioning total knee prostheses (11 contemporary mobile-bearing type, 11 posterior-stabilized type) were determined. Polyethylene wear particles were isolated from synovial fluids and examined by scanning electron microscopy. Particle size (equivalent circle diameter) was 0.81 +/- 0.12 microm (mean +/- standard error) in mobile-bearing types and 0.78 +/- 0.08 microm in posterior-stabilized types. Particle shape (aspect ratio) was 1.94 +/- 0.13 in mobile-bearing types and 2.30 +/- 0.22 in posterior-stabilized types. Total numbers of particles were (1.75 +/- 1.02) x 10(8) in mobile-bearing and (1.16 +/- 0.57) x 10(8) in posterior-stabilized types. The differences in these parameters between the two groups were not statistically significant. In the early stages after surgery, contemporary mobile-bearing types were comparable to posterior-stabilized types in terms of polyethylene wear-particle generation. The present results do not support the proposition that has been put forward in the literature; namely, that the contemporary mobile-bearing design has an advantage, in terms of the polyethylene wear rate. These data suggest that the advantage of complete conformity in the femoro-tibial articulating surface of contemporary mobile-bearing design may be offset by wear of the mobile undersurface and slot, apart from the articulating surface.

Aged↗
PubMed1983

Tissue response to carbon-reinforced polyethylene.

There has been clinical concern about the gray discoloration in synovial tissue adjacent to carbon-reinforced polyethylene total joint implants. To evaluate the pathologic response of the synovium to this material, synovial specimens from 11 total ankle cases with carbon-reinforced tibial components and two synovial specimens from cases with standard polyethylene tibial components were studied by gross and histologic techniques. Polyethylene debris was found to produce a significant synovial reaction with histiocytes and foreign body giant cells. This was found in both the carbon-reinforced cases and in those cases without carbon-reinforced components. This reaction is also seen in revisions of total hips and total knees in which standard polyethylene components have been implanted. In contrast with this, carbon particles produced only a minimal reaction in the synovial tissue. Carbon appears to be an extremely benign implant material, and synovial discoloration from shed carbon fibrils does not appear to present a significant clinical problem.

Adult↗