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The incorporation of high-performance polyethylene fibre into acrylic denture-base resin produced a very significant decrease in the processing shrinkage of the material, explained by the highly anisotropic mechanical and thermal properties of the fibres.
It has been advocated that the use of contrast acrylic bone cement (namely, a cement in which a suitable additive is included) for the fixation of a cemented arthroplasty will facilitate its revision (should this be necessary). It is useful, therefore, to determine the extent to which each of the relevant mechanical properties of the cement is affected by the presence of such an additive. It is shown, in the present work, that the addition of one contrast agent (an aqueous methylene blue solution) to a cement has no statistically significant effect on its mode-I plane-strain fracture toughness. This strengthens the case for the use of contrast cement for the aforementioned application.
A copolymer containing 88% 2-hydroxyethyl methacrylate (HEMA), 9% poly(ethylene glycol) (MW 18.5 kDa) tetra-acrylate and 3% ethylene dimethacrylate was prepared and evaluated for use as a biocompatible interface between glucose biosensors and tissue in the rat. The glucose sensor utilizes glucose oxidase that is electrically 'wired' to a gold current collector by a reduction-oxidation polymer. Coatings of the copolymer were crosslinked in situ on the sensors using long wavelength ultraviolet light and 2,2-dimethoxy-2-phenyl-acetophenone as the initiator. The effect these films had on the current response to glucose was measured. Over a glucose concentration range of 0-30 mM, the average percentage decrease in response was 45 +/- 28% (mean +/- 95% confidence interval) at 37 degrees C for films that were about 0.1 mm thick, an acceptable value. Copolymer-treated and control electrodes were implanted in the intrascapular subcutaneous tissue of male Sprague-Dawley rats for three days. The explanted samples were evaluated using scanning electron microscopy. The control electrodes were highly encapsulated with fibrous material, while the copolymer-treated electrodes induced much less encapsulation. The results show this copolymer to be a candidate as a biocompatible coating for electrically wired oxidoreductase-based subcutaneous biosensors.
A range of hydrogels were prepared by blending aqueous solutions of poly(vinyl alcohol-vinyl acetate) with poly(acrylic acid) in various proportions. The effects of two cross-linking agents (glyoxal and glutaraldehyde) and subsequent thermal treatment on the properties of the blends are discussed. Dynamic mechanical analysis (DMA) of the xerogels indicated complete miscibility of the various blends which was evident from the appearance of a single glass transition temperature (Tg) in the presence of either glyoxal or glutaraldehyde at all thermal treatments studied. A 50/50% wt/wt blend was found to have the highest storage modulus and was thus selected for further study. Hydrogels prepared with glutaraldehyde without subsequent thermal treatment exhibited higher storage modulus values than those prepared using glyoxal when tested isothermally at 20 degrees C in a water bath. A further increase in the storage modulus was observed when these hydrogels were thermally treated at 120 or 150 degrees C. In a non-isothermal study on the cross-linked hydrogels, no variation in storage modulus was observed. Broad peaks were observed in tan delta plots, these peaks shifting towards higher frequencies as the degree of cross-linking increased in the hydrogel.
N-Acryloyl-N'-phenylpiperazine is a promoter of redox reactions synthesized recently, and proposed as an activator for the polymerization of acrylic resins for biomedical use. The chemical was analyzed for different genotoxicity endpoints, to obtain both information on its possible mutagenic/carcinogenic potential and a model analysis of a tertiary arylamine, which belongs to a class of chemicals commonly used as polymerization accelerators in the biomaterial field. The genotoxicity endpoints considered were: gene mutation in the Salmonella test; structural and numerical chromosome alterations in Chinese hamster V79 cells, evaluated by the micronucleus test together with an immunofluorescent staining specific for kinetochore proteins; in vitro and in vivo DNA damage, evaluated in V79 cells and in mouse liver by the alkaline DNA elution technique. On the whole, the results indicate that N-acryloyl-N'-phenylpiperazine is to be regarded not so much as a DNA-damaging agent, but as a genomic mutagen. Indeed, it was not mutagenic in Salmonella (though its toxicity did not allow testing concentrations over 70 micrograms/plate), and it was weakly positive in inducing chromosomal fragmentation in vitro (one positive, not dose-related, result out of five different doses tested) and in vivo DNA damage (increases in DNA elution rate never doubling control values). The chemical was, however, clearly positive (with dose-dependent effects up to about 25 times the control value) in causing numerical chromosome alterations, at the maximal non-toxic doses.
The use of powders, composed of a mixture of a chlorine-releasing agent with highly absorbent acrylic resin, for disinfecting body fluid spills was evaluated by laboratory tests. 'Encap' and 'Red Z' were found to absorb rapidly up to 200 ml of water to form a semi-solid gel. When experimental formulations containing 1%, 5% and 10% available chlorine were evaluated by a standardized surface test, those containing 10% gave the best results. The ease and rate of absorption of fluids by these formulations decreased as the fluid consistency increased and they seem more suitable for watery spills than for blood. The use of a powder based on peroxygen compounds ('Virkon') for disinfecting contaminated spills was evaluated by laboratory tests and hospital trials. Laboratory tests showed that 'Virkon' is strongly and rapidly bactericidal. In hospital ward trials by nurses using 'Virkon' on both natural and artificial spills, 60 of 62 contact plates pressed on to decontaminated surfaces proved negative, and no unpleasant fumes were generated when 'Virkon' was applied to urine. In another trial, 1% 'Virkon' solution proved very effective in decontaminating mortuary tables. Antiviral activity was not tested.
A technique is described for the prosthetic replacement of two fingers using acrylic resin. Retention was obtained using finger rings. The stages of the technique are outlined. Advantages and disadvantages are briefly stated.
Results of in vivo metabolism studies with acrylic acid (AA) have indicated that 60-80% of the administered dose is excreted as CO2 within 2-8 hr of oral dosing of rats; however, the pathway of AA metabolism to CO2 in mammals has not been determined. To define this route, rat hepatocytes were isolated and incubated with [1-14C]AA in a sealed vial modified to trap evolved 14CO2. Rapid oxidation of AA to CO2 was observed. Similar incubations conducted with rat liver homogenates fortified with ATP, ADP, coenzyme A, carnitine, and malate also resulted in oxidation of AA. Mitochondria isolated from liver homogenates were incubated with AA under the same conditions and yielded higher rates of AA oxidation than homogenates. Addition of equimolar amounts of propionic acid, 3-hydroxypropionic acid, or 3-mercaptopropionic acid significantly inhibited the oxidation of AA by mitochondria. HPLC analysis of the mitochondrial incubation mixtures indicated that a single major metabolite, which coeluted with 3-hydroxypropionate, accumulated in the solution. The results indicate that AA is rapidly incorporated into a mitochondrial pathway for propionic acid catabolism that results in the release of CO2 and possible bioincorporation as acetate. This pathway appears to be the principal route of detoxification of AA in mammals.
The comparative neurotoxicity of subchronic exposure to 2-hydroxyethyl acrylate (HEA) and acrylamide (ACR) was evaluated using a functional observational battery (FOB) and neuropathology. Three dose levels of each compound (HEA: 3, 20, 60 mg/kg; ACR: 1, 4, 12 mg/kg) were administered intraperitoneally to male and female Long-Evans rats (n = 10/sex/dose level), 5 days/week for 13 weeks. Two vehicle control groups were also included. The FOB, which includes home-cage and open-field observations and interactive tests of sensory, neuromuscular, and autonomic function, was administered before dosing, at monthly intervals, and on the day after the last dose. Subsets of rats (n = 6/sex/dose level) were then perfused and tissues from the brain, spinal cord, and peripheral nerve were prepared for light microscopic evaluation. There were clear differences between the effects of HEA and ACR. ACR produced time- and dose-related changes in FOB measures of muscle tone and equilibrium, and produced axonal degeneration in peripheral nerves and within long tracts of the spinal cord. HEA exposure was also associated with changes in muscular function on FOB testing, but the magnitude of the effects was not as great as with ACR and not dose related. In addition, no neuropathological changes were detected after HEA exposure. Thus, the effects of HEA did not resemble those of ACR. The FOB data were summarized in domains of neurobehavioral functions. Using a composite score analysis, ACR was shown to produce prominent effects in the neuromuscular domain whereas HEA was largely without effect. When the data are analyzed in this manner, the neurotoxic potential of HEA appears to be minimal.
The disposition of [1-14C] acrylic acid (AA) was characterized in the male Sprague-Dawley rat following oral administration, by gavage in water, at 400 mg/kg and topical application, in acetone, at 501 micrograms/cm2. The oral dose was well absorbed, rapidly and extensively metabolized, and excreted primarily (approx. 80%) as 14CO2 within 24 hr of administration. The rate and extent of 14CO2 evolution from [14C]AA was greater for [1-14CAA] while a significantly lower proportion of the dosed radioactivity remained in the tissue of animals than that reported for [2,3-14C]AA (Winter et al., Drug Metabolism and Disposition 1992, 20, 665). This is consistent with incorporation of AA into a minor beta-oxidation pathway of mitochondrial propionate metabolism by which AA may be metabolized to CO2 or incorporated into cellular constituents. Approximately 5% of the dosed radioactivity was excreted in the urine. The disposition of [1-14C]AA following dermal application was studied using charcoal-containing traps attached to the back of the rats to trap volatilized AA from the dosing sites. Following application of 100 microliters AA [4% (v/v) in acetone] to an area of 8.4 cm2 of the skin of a rat (501 micrograms/cm2), the majority (about 73%) of the dose volatilized and was recovered in the charcoal trap. Percutaneous absorption of AA that did not volatilize was rapid and appeared to have the same metabolic fate as AA administered orally with about 75% of the absorbed dose excreted as 14CO2 within 24 hr.
A 2 yr carcinogenicity study of 2-ethylhexyl acrylate (2-EHA) was conducted by applying 25 microliters 21.5, 43 or 85% 2-EHA or 0.015% benzo[a]pyrene (B[a]P) in acetone, three times/wk, to the clipped dorsal skin of male NMRI mice (80 per group). A further group received acetone and served as the vehicle control. After about 7 months of treatment, half of each group was rested from treatment for a period of 2 months, then treated with the promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) for 20 wk followed by observation until termination of the study. The other half of each group received continuous treatment with 2-EHA, B[a]P or acetone, respectively, for 2 yr. Signs signs of skin irritation were apparent in all groups treated with 2-EHA [hyperkeratosis, hyperplasia (acanthosis), crust formation and ulceration]. In the group treated with B[a]P alone or B[a]P with TPA, 79% and 67% of the mice, respectively, bore squamous cell carcinomas. None of the mice treated with acetone or 2-EHA alone developed a skin tumour at the application site. One squamous cell papilloma occurred in each of the groups treated with 2-EHA and TPA, an incidence matched by the single squamous cell papilloma in an untreated area of an acetone control mouse. Thus, 2-EHA proved not to be carcinogenic in the skin of male NMRI mice by epicutaneous administration.
A range of non-toxic polysaccharides were screened for their ability to prevent bacterial adhesion to denture acrylic in vitro. Sodium alginate, karaya gum and carrageenan were found to be the most effective, reducing adhesion of Streptococcus salivarius by 98.7, 97.9 and 99.2 per cent respectively. These three polysaccharides were then tested for their ability to reduce the number of bacteria adhering to dentures in vivo. Sodium alginate was the most effective, reducing the attachment of bacteria to the palate-contacting surface of the denture after 5 h of normal wear by 84 per cent compared with uncoated controls. The results of this investigation suggest that the accumulation of denture plaque may be prevented by frequent application of a renewable, sacrificial coating of a non-toxic polysaccharide.
The literature relating to the determination of the bond strength of plastic denture teeth to acrylic resin denture material is reviewed. The papers are presented in chronological order with information on specimen preparation, batch sizes and methods of testing. The lack of uniformity in experimental techniques and the diverse range of products assessed makes recommendations for laboratory practice difficult to formulate. One consistent observation is that tooth surface contamination with wax decreases the bond strength between the teeth and the denture base material. A universal testing method needs to be formulated to replace the various techniques now employed.
OBJECTIVES AND METHODS: The curing of several commercial powder/liquid mixtures of acrylic denture base materials was carried out at different temperatures and curing times. The levels of residual monomer, tensile strength, percentage elongation before break and water absorption were measured. RESULTS AND CONCLUSION: It was found that the level of residual monomer determined by gas-liquid chromatography decreased with curing time and temperature increase. At the same time, the tensile strength was improved and water absorption decreased.
A thin re-usable stainless steel ophthalmic applicator is described. The radioactive Iodine-125 sources are inserted in an acrylic button which fits neatly into a stainless steel shell 1 mm thick. The applicator can be assembled with the radioactive sources precisely positioned without the use of adhesives or mechanical devices such as clamps or screws in a matter of a few minutes, (under sterile conditions if necessary). The applicator can be dismantled in seconds after which it is ready for cleaning and re-sterilization. The overall thickness of the plaque is 2.6 mm, but this has the potential to be reduced to 2.1 mm. Suture holes are provided on a flange subtending 120 degrees around the circumference of the shell and are exactly matched on a stainless steel template.
The effect of sub-inhibitory concentrations of antifungal drugs on the adherence of Candida albicans to acrylic surfaces was investigated. Among five antifungals tested, azalomycin F and aculeacin A significantly enhanced the adherence. The zeta-potential of fungal cells was affected by antifungal drugs, whereas no significant change in cell surface hydrophobicity was observed. The relationship obtained between the change in the adherence and that in zeta-potential suggests that the enhanced adherence was caused by decreased electric repulsive forces.
We report rates of acrylic acid (AA) oxidation and tissue/blood partition coefficients in rat tissues. AA oxidation in Fischer 344 rat kidney and liver slices was described by saturable kinetics with maximal velocities of about 4 and 2 mumol/h/g, respectively. AA oxidation rates in 11 additional tissues were 40% or less than in liver. AA oxidation rates in Sprague-Dawley rat liver and kidney were similar to those in Fischer rats. Partition coefficients varied within a narrow range, suggesting that a tissue's contribution to systemic detoxification of AA will depend much more strongly on its rate of AA oxidation and the proportion of the cardiac output that it receives.
A simple and efficient procedure has been developed for the derivatization of diuretic agents in human urine by direct extractive alkylation and their detection by gas chromatography-mass spectrometry. The procedure is an improvement over previous extractive alkylation methods because of the development of a simple clean-up step using a macroreticular acrylic copolymer (SM-7 resin) to remove the coextracted phase-transfer reagent from the organic phase after derivatization. With 1 ml of sample the method gives detection limits in the range 10-50 ng/ml for acetazolamide, probenecid, dichlorphenamide, hydroflumethiazide, furosemide, chlorthalidone, bumetanide, hydrochlorothiazide, quinethazone, bendroflumethiazide, metolazone and cyclopenthiazide.