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Results for “Polymethyl Methacrylate”

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At least 73 records · Page 4Linked to original sources
PubMed2001

Intravenous polymethyl methacrylate after cemented hemiarthroplasty of the hip.

Current cementing techniques used during hip arthroplasty aim to maximize the bond at the bone-cement interface in an effort to increase the longevity of the prosthesis. To accomplish this, one must generate high intramedullary pressures, which are known to be associated with complications such as cement implantation syndrome. We record a rare complication following cement pressurization of a hip hemiarthroplasty that resulted in intravenous polymethyl methacrylate (PMMA). This complication however, is not associated with a significant morbidity or mortality, but it is important to identify and distinguish from a femoral cortical defect, which can be created during surgery.

Aged↗
PubMed2006

Electrophysiological recordings of single ion channels in planar lipid bilayers using a polymethyl methacrylate microfluidic chip.

Planar lipid bilayers are used for functional studies of ion channel proteins using electrophysiological techniques. We have been developing a plastic micro-fluidic device for the reconstitution of planar lipid bilayers and electrophysiological recordings toward a "membrane protein chip" for high-throughput screening. In the previous report [Suzuki, H., Tabata, K.V., Noji, H., Takeuchi, S., 2006. Highly reproducible method of planar lipid bilayer reconstitution in polymethyl methacrylate microfluidic chip. Langmuir 22 (4), 1937-1942], we presented the method and device in which the reproducibility of planar lipid bilayers reached 90%, and multiple bilayers were formed simultaneously. In this communication, we show that our device has excellent electric properties suitable for ion channel analysis down to single molecular level. Additional aspects on the optical accessibility and controllability on lipid bilayer formation are also presented.

Electrochemistry↗
PubMed1994

In vitro micronucleus induction by polymethyl methacrylate bone cement in cultured human lymphocytes.

Human lymphocytes cultured in vitro were used to assess the ability of polymethyl methacrylate (PMMA), currently used in orthopaedic surgery as bone cement, to induce micronuclei in binucleated cells. The results of the study show a significant increase in the micronucleus frequency in treated cultures and therefore the genotoxic effect of PMMA bone cement or its ingredients (methyl methacrylate, dimethyl para-toluidine and hydroquinone) usually present in self-curing methacrylate bone cement and released in small quantities after polymerisation. This effect is evident during the stage immediately after the polymerisation process, and after a certain period of time (5 days in our experimental model).

Adult↗
PubMed1996

Rapid-processing procedure for heat polymerization of polymethyl methacrylate in a pressure cooker with automatic controls.

This study introduces a new rapid-processing procedure for curing polymethyl methacrylate denture base resin in an automatically controlled pressure cooker. The cooker filled with water was inflated with 6 kgf/cm2 air pressure and heated to 120 degrees C (248 degrees F) and maintained for 10 minutes. No significant differences were found between the new pressure cooker method and the conventional method for surface hardness and porosity (p > 0.05). The pressure cooker significantly shortened polymerization time, and the polymerization is controlled automatically.

Air Pressure↗
PubMed1984

Comparative physiologic performance of polymethyl methacrylate and gas-permeable contact lenses.

A short-term study of the physiologic response of the cornea to polymethyl methacrylate (PMMA) contact lenses and hard, gas-permeable contact lenses of different materials (polycon and Menicon 02), thicknesses, and fittings, was carried out on nine unadapted subjects using one eye as the experimental eye and the other as the control eye (no lens). Changes in corneal thickness were monitored at seven locations across the cornea using an electronic micropachymeter. It was found that gas-permeable lenses produced less corneal swelling than the PMMA lenses. However, lens thickness and the fit of the lens were still important control variables with these gas-permeable lenses. The thin gas-permeable lens produced less swelling than thicker lenses, and the flatter fitting gas-permeable lenses produced less swelling than the steeper fitting lenses. The swelling with all the hard lenses studied was confined primarily to the central 6 mm of the cornea.

Adult↗
PubMed2005

Biological compatibility of polymethyl methacrylate, hydrophilic acrylic and hydrophobic acrylic intraocular lenses.

PURPOSE: Extensive clinical investigations of the biocompatibility of different intraocular lenses (IOLs) have been made in an effort to optimize the outcome of modern cataract surgery. The aim of this study was to add animal eye experimental implantation data regarding cellular reaction on the anterior surface of IOLs. METHODS: Thirteen adult albino rabbits had phacoemulsification/aspiration of the crystalline lens followed by implantation of a posterior chamber IOL in each eye. Three types of IOLs were studied: Hydroview (Bausch and Lomb; n = 7), Acrysof (Alcon, USA; n = 7), and polymethyl methacrylate (PMMA; HOYA, Japan; n = 7). The animals were killed by intravenous pentobarbital 1, 4, or 8 weeks later. The IOLs were explanted and stained with hematoxylin and eosin, and observed under a light microscope. The shape of mouse ascites-induced macrophages on the anterior surface of the three different IOL types (Hydroview, PMMA, and Acrysof) was studied after 24 h of oven culture. RESULTS: Hydrophilic acrylic IOLs showed the highest affinity for lens epithelial cell (LEC) outgrowth, and the lowest and slowest maturation rate reaction of macrophages. PMMA IOLs showed the lowest affinity for LEC outgrowth, and the highest reaction of macrophages. Hydrophobic acrylic IOLs showed intermediate results both regarding LECs and macrophages. CONCLUSIONS: Results suggest that IOL biomaterial properties are the key factor that influences the quantity of monocytes/macrophages as well as the process of their maturation/senescence. LEC outgrowth is influenced both by the biomaterial of IOLs and by the monocyte/macrophage reaction.

Acrylic Resins↗
PubMed1989

Lack of sister-chromatid exchange induction by polymethyl methacrylate bone cement in human lymphocytes cultured in vitro.

Human lymphocytes cultured in vitro were used to assess the ability of polymethyl methacrylate (PMMA), currently used in orthopedic surgery as bone cement, to induce sister-chromatid exchanges (SCE). Under the conditions used in this study, PMMA bone cement did not produce any significant increase in SCEs in phytohemagglutinin-stimulated human lymphocytes. However, a significant decline (p less than 0.05) in the proliferation rate index was observed, which might be an indicator of the cytotoxic effect of PMMA.

Adult↗
PubMed1987

In vitro research on the possibility of chromosomal damage caused by polymethyl methacrylate in orthopaedics. A preliminary report.

There are few experimental studies in the literature concerned with evaluating the toxic effect of polymethyl methacrylate. Because of the number of patients who are now carriers of this substance, it seems important to ascertain whether or not it could cause chromosomal damage. This study reports the preliminary data obtained from an in vitro technique on human lymphocytes placed in contact with different concentrations of methyl methacrylate and its polymerized form. The method consists of an analysis of the exchanges of DNA tracts in the chromosomes of these lymphocytes; the increase in the frequency of exchange as compared to that in the controls is an indication of the mutagenic effect. A slight increase in the average frequency of isochromatid exchanges in the lymphocytes cultivated with the monomer was observed, and this deserves closer study. However, this preliminary data would appear to exclude the existence of chromosomal damage.

Adult↗
PubMed1996

Embedding undecalcified bone in polymethyl methacrylate: an improved method.

A number of improvements are described for the preparation of resin sections of undecalcified bone embedded in polymethyl methacrylate. Based on a modified resin mix, the modifications, which include a specially designed block clamp, have resulted in a simplified and quicker procedure with improved section quality. The method has been used routinely for investigating approximately 10,000 cases of metabolic bone disease for diagnostic purposes.

Bone Diseases, Metabolic↗
PubMed1981

Treatment of bone and soft-tissue infections with gentamicin-polymethyl-methacrylate chains. A review of clinical trials involving 1 500 cases.

In vitro and in vivo experimental work showed that gentamicin-polymethyl-methacrylate (G-PMMA) provides bactericidal gentamicin concentrations at the site of infection but very low systemic concentrations, suggesting advantages as regards infection control and lack of side-effects. During the past 4 years 1247 osteomyelitis patients have been treated with G-PMMA at 11 clinics. The early postoperative results showed control of infection in 90.8% of cases. Infection persisted in 9.2% owing to remaining sequestra, osteosynthetic material, etc. This indicates the importance of good and radical surgery. Follow-up of 355 patients for 3 - 54 months postoperatively showed relapses in only 27 cases. A total of 361 patients with soft-tissue infections (e.g. associated with bone infections, sacral cavity after rectum excision, abscesses, etc.) underwent treatment with G-PMMA after thorough debridement, with good results. Techniques for implantation, and removal of the chains are discussed. No adverse effects have been observed in this series of trials.

Animals↗
PubMed1989

Residual ethylene oxide determination in polymethyl methacrylate disks and intraocular lenses by headspace gas analysis and N,N-dimethylformamide extraction.

The residue in an ethylene oxide (EO)-exposed polymethyl methacrylate (PMMA) material [flat disk and intraocular lens (IOL)] was determined using three methods: semiautomatic and manual headspace methods and N,N-dimethylformamide (DMF) solvent extraction. Results from the analysis of three different sample configurations at three different EO concentrations are compared. Results from the DMF extraction of PMMA indicate that the headspace methods at 100 degrees C are not exhaustive with respect to recovery of total residual ethylene oxide. Furthermore, the manual headspace method appears to be slightly more effective than the semiautomatic injection headspace method. Sorption of EO and subsequent extraction is related to the surface area-to-volume ratio of the sample, with higher concentrations observed in samples with the high ratio.

Autoanalysis↗
PubMed1995

Bonding of resin teeth to the polymethyl methacrylate denture base material.

The objective of this study was to compare bonding of acrylic resin teeth treated in various ways to the polymethyl methacrylate (PMMA) denture base material. The joint surface of each acrylic tooth cured to heat-cured or autopolymerizing PMMA was either untreated, ground, or adjusted with mechanical retention. The bond to the PMMA was tested with a three-point loading test. To determine whether the bond failure was adhesive or cohesive, the fracture surfaces were analyzed visually and by scanning electron microscopy. The highest bond strength to both the heat-cured and the autopolymerizing PMMA was obtained by grinding grooves on the joint surface of an acrylic resin tooth before it was cured to the PMMA (p < 0.001). Heat-cured PMMA did not adhere to the acrylic resin tooth better than the autopolymerizing PMMA did (p > 0.05).

Acrylic Resins↗
PubMed1979

Silver polymethyl methacrylate antibacterial bone cement.

An improved antibacterial bone cement was sought based on the addition of low concentrations of inorganic silver compounds to polymethyl methacrylate. Composites with AgCl, Ag-AgCl, Ag2O, Ag2SO4 and Ag3PO4 in concentrations of 0.05% to 1% by weight, were tested in vitro against bacterial cultures. All were effective, but Ag2SO4 was especially so, even after 7 weeks of incubation in normal saline. Compressive strength of the cement was not affected by these additions, except in the case of Ag2O. Biocompabibility tests in rabbit muscle for up to 12 weeks showed no significant difference between the Ag -PMM and plain PMM in tissue reactivity, both being minimal. These features, coupled with the broad spectrum of antibacterial activity and low allergic potential of silver, make Ag-PMM an attractive alternative to conventional organic antibiotic/bone cement composites.

Acrylic Resins↗
PubMed1991

Macrophage exposure to polymethyl methacrylate leads to mediator release and injury.

To understand further the role of macrophages in the loosening of cemented arthroplasty, several in vitro effects of polymethyl methacrylate (PMMA) particle exposure in these cells were studied. The kinetics of arachidonic acid and derived inflammatory mediator release was characterized following macrophage exposure to either PMMA or control polystyrene particles. Temporal release of radiolabeled products by [14C]arachidonate-labeled cells was determined by sequential scintillation counting. Significant dose-dependent release of arachidonic acid mediators by macrophages was observed within half an hour of exposure to either PMMA or styrene particles. Unexposed control cells incubated in media alone did not release detectable amounts of radiolabeled products. The leakage of intracellular lactate dehydrogenase (LDH), a marker of cell injury, was detected spectrophotometrically 4 h following exposure to PMMA but not styrene. PMMA-induced LDH release was dose dependent. In contrast, polystyrene exposure failed to increase LDH release above unexposed control cells. These in vitro studies reveal that macrophages rapidly released arachidonic acid and derived inflammatory mediators in response to both PMMA and styrene particles. However, cells exposed to PMMA are lethally damaged, as reflected by the subsequent leakage of their intracellular LDH. We propose that a similar sequence of events may occur when macrophages encounter PMMA particles at the bone-cement interface. This is characteristic of a foreign body granulomatous response.

Animals↗
PubMed1992

An infrared study of the interaction of polymethyl methacrylate with the protein and mineral components of bone.

We used Fourier transform infrared (FT-IR) microscopic mapping techniques to investigate the infiltration of polymethyl methacrylate (PMMA), a widely used medium for embedding biological tissues, into rat femur sections. Monitoring of the infrared absorbances of the PMMA carbonyl stretch, the protein amide I, and the apatite mineral phosphate stretch over a 225 x 975-microns region of the epiphyseal growth plate region of the rat femur enabled comparison of the relative amount of each component in distinct regions of the tissue. It was found that PMMA penetrates less into regions of greater mineral density and that the frequency of the PMMA carbonyl absorbance from the embedded tissue, 1729 cm-1, is identical to the free PMMA carbonyl frequency. This is consistent with a diffusion mechanism of infiltration of the PMMA, with no specific chemical interaction between the PMMA and the tissue components.

Animals↗
PubMed1996

Dimensional accuracy and stability of polymethyl methacrylate reinforced with metal wire or with continuous glass fiber.

The aim of this study was to determine the dimensional accuracy and stability of denture base polymethyl methacrylate (PMMA), which was reinforced in various ways. Autopolymerizing PMMA and heat-cured PMMA were reinforced either with semicircular steel wire or with a prefabricated experimental reinforcement made of continuous E-glass fiber. Control specimens had no reinforcement. The width of each U-shaped test specimen was measured with a digital micrometer under a light microscope immediately after the test specimen was cured and when stored in water for 1, 2, 7, and 14 days. The results revealed that both the type of PMMA and the type of reinforcement affected the dimensional accuracy of the test specimens, especially after 7 and 14 days in water storage (p < 0.001). The greatest dimensional accuracy was found with the unreinforced test specimen made from autopolymerizing PMMA and with test specimens reinforced with the metal wire made from heat-cured PMMA. In terms of the width of the test specimens, the lowest dimensional accuracy was found in unreinforced and glass fiber reinforced specimens made from heat-cured PMMA. Storage in water did not affect the stability of the width (p > 0.1). The results suggest that the polymerization shrinkage of PMMA causes lower dimensional accuracy of the test specimens reinforced with glass fiber. This should be considered when glass-fiber reinforcement is used clinically.

Analysis of Variance↗
PubMed1993

Long-term results of sutureless phacoemulsification with implantation of a 7-mm polymethyl methacrylate intraocular lens.

In an attempt to minimize postoperative astigmatism while retaining the advantages of implanting intraocular lenses with large optics, sutureless phacoemulsification with implantation of a 7-mm polymethyl methacrylate intraocular lens was performed through a modified scleral tunnel in 100 consecutive patients. Visual and keratometric results, as well as complications, were recorded during a follow-up period of 12 months. Average uncorrected visual acuity improved from 20/153 before surgery to 20/66 as early as 1 week after surgery. Average best corrected visual acuity improved from 20/86 before surgery to 20/39 as early as 1 week after surgery. No significant changes in visual acuity were recorded thereafter. The absolute value of keratometric astigmatism was not increased significantly at any postoperative examination time. The induced cylinder shifted from 1.26 diopters x 74.40 degrees at 1 week to 1.22 D x 1.50 degrees at 1 month after surgery, without further relevant changes thereafter. Mean (+/- SD) endothelial cell loss was 7.2% +/- 6.1% at 1 month and 12.2% +/- 5.4% at 6 months after surgery. Corneal thickness was not increased significantly at any postoperative examination time. Implantation of intraocular lenses with large optics through a scleral tunnel allows quick visual rehabilitation as well as early stability of refraction.

Adult↗