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At least 613 records · Page 34Linked to original sources
PubMed2005

Preparation and photophysics of 2-(1-pyrenyl)acrylic acid and its methyl and 2',2',6',6'-tetramethyl-4'-piperidyl esters.

Novel probes represented connection of pyrene as chromophore and sterically hindered amine stabilizers (HAS) in the form of esters of 2-(1-pyrenyl)acrylic acid were synthesized. HAS was in the form of parent amine (PAP) as well as stable nitroxyl radical form (PAP-NO.). Photophysics of these probes were compared with their precursor as 2-(1-pyrenyl)acrylic acid (PAA) and its methyl ester (PAM). The fluorescence spectrum of PAA strongly depends on the acidity of the solution. The spectrum in neutral methanol indicates that it originates from the anionic form -COO(-). Changes of acidity or basicity of methanol solution resulted in the changes of shape, position as well as the intensity of fluorescence band. This is due to the presence of protolytic equilibria, either in the ground state or in the singlet excited state, leading to the formation of molecular form -COOH and the cationic form -COOH(2) (+). The ester analogues did not show any changes in various pH conditions. Fluorescence of all probes depends on the polarity of solvents and the presence of oxygen. Intermolecular quenching was studied with external quenchers TEMPO and oxygen and the data were compared with the intramolecular quenching using 1'-oxo-2',2',6',6'-tetramethyl-4'-piperidinyl-2-(1-pyrenyl)acrylate (PAP-NO.).

Journal Article↗
PubMed1989

The effectiveness of two disinfectants on denture base acrylic resin with an organic load.

This study compared the biocidal effectiveness of chlorine dioxide and 5.25% sodium hypochlorite (diluted 1:10) on acrylic resin strips inoculated with Staphylococcus aureus, Candida albicans, or Escherichia coli in the presence of an organic load. Sterile acrylic resin strips were immersed in a solution containing 10% horse serum and 10(5) to 10(7) organisms/ml for each type of organism, then disinfected in chlorine dioxide, sodium hypochlorite, or 0.9 sterile saline for 30 seconds or 1, 2, or 4 minutes. After disinfection, the strips were neutralized and incubated for 72 hours. The results showed a difference between the ability of chlorine dioxide and sodium hypochlorite to kill the test organisms on acrylic resin strips when organic matter is present. Chlorine dioxide achieved complete disinfection of all three organisms within 2 minutes. Sodium hypochlorite achieved complete disinfection of all three organisms within 4 minutes.

Bacteria↗
PubMed1994

Acrylic resin-fiber composite--Part II: The effect of polymerization shrinkage of polymethyl methacrylate applied to fiber roving on transverse strength.

This study determined the effect of polymerization shrinkage of polymethyl methacrylate (PMMA) coating of fiber roving on the transverse strength of an acrylic resin-glass fiber composite. The test specimens were heat-cured acrylic resin reinforced with glass fibers. The glass fiber rovings were treated with four PMMA-MMA mixtures (30 specimens per group) of various ratios assumed to have different amounts of polymerization shrinkage. A transverse strength test was used to determine the fracture resistance of the test specimens and the polymerization shrinkage of the PMMA-MMA mixtures was measured. After the specimens were fractured, single glass fibers used to reinforce the test specimens were studied by SEM. The fracture resistance of the specimens was statistically different (p < 0.001) among treatments, and the polymerization shrinkage of the PMMA-MMA mixture also varied as the calculations predicted. The SEM micrographs showed differences in thickness of the acrylic resin layer on the surface of the fibers with PMMA-MMA mixtures of various ratios. According to the results, the ratio that caused only minor polymerization shrinkage of PMMA in the glass fiber roving improved the fracture resistance of the test specimens and seemed to increase the amount of PMMA inside the fiber roving.

Analysis of Variance↗
PubMed1984

The synovial response to intra-articular acrylic cement particles in guinea pigs.

The histology and cytology of the tissue response to intra-articular insertion of particles of acrylic bone cement containing barium sulphate has been studied in the guinea pig knee joint. Following insertion of the acrylic, fibrinous debris admixed with particles became adherent to the synovial membrane. Cell proliferation at the interface between the debris and the synovial tissue engulfed the debris, and a new layer of intimal lining cells formed over its surface. This process led to incorporation of the particles into vascularized subintimal tissue. The response to subintimal acrylic cement particles was by multinucleate giant cells (macrophage polykaryons), macrophages and fibroblasts, with a variable amount of intermingled fibrosis. After incorporation was complete, the long-term (3 months to 1 year) subintimal response acquired a basically stable histological appearance amongst which no zones of tissue necrosis were found. However, in some instances it did contain foci of neutrophil infiltration, and it is possible that such foci are a reaction to minor episodes of cell damage.

Animals↗
PubMed1989

Cyanide, carboxyhemoglobin and blood acid-base state in animals exposed to combustion products of various combinations of acrylic fiber and gauze.

In order to examine the usefulness of blood cyanide concentrations as an indicator of whether or not a victim was alive at the start of a fire, blood cyanide concentrations were measured in the bodies that we autopsied in our institute between January 1986 and March, 1987. In the present study, bodies with advanced decomposition were excluded. Thirty-six bodies were included: cyanide as well as carboxyhemoglobin (COHb) were detected in four charred bodies found at the scene of a fire. On the other hand, cyanide was not detected in any of the remaining 30 bodies except in two cases suspected of having ingested a cyanide compound. Rats and rabbits were made to inhale the combustion products of various combinations of acrylic fiber (hydrogen cyanide generating material when heated) and gauze (carbon monoxide generating material when heated). The exposure to the combustion products was continued until death in the rat and until apnea in the rabbit. The concentration of hydrogen cyanide in the exposure chamber and that of blood cyanide, at the time the animal died, correlated with the amount of acrylic fiber heated. In addition to differences in blood COHb and cyanide concentrations, there were also differences in blood gas concentrations between the acrylic fiber and the gauze groups. When the rabbits were switched to room air after the occurrence of apnea, the blood gas value began to normalize.

Aged↗
PubMed2005

Development of highly reactive mono-(meth)acrylates as reactive diluents for dimethacrylate-based dental resin systems.

Reactive diluents such as triethyleneglycol-dimethacrylate (TEGDMA) have been widely used with bisphenol-A-glycidyl-dimethacrylate (Bis-GMA) to achieve restorative resins with appropriate viscosity and higher conversion. However, additional water sorption and polymerization shrinkage were also introduced. The aim of this work is to investigate whether the cure and material properties can be improved in dental resins containing novel mono-(meth)acrylates as reactive diluents so that these Bis-GMA-based copolymers have reduced polymerization shrinkage but higher overall double bond conversion. Several ultra-high-reactivity mono-(meth)acrylates that contain secondary functionalities have been synthesized and investigated. The polymerization rate and double bond conversion were monitored using photo-FTIR. Polymerization shrinkage, dynamic mechanical analysis, and flexural strength were characterized. Compared with the Bis-GMA/TEGDMA control, the Bis-GMA/mono-methacrylate systems studied showed higher final conversions, faster curing rates, and decreased polymerization shrinkage. Our optimum system Bis-GMA/morpholine carbamate methacrylate achieved 86% final conversion (vs. 65%), a polymerization rate 3.5 times faster, and a 30% reduction in polymerization volumetric shrinkage. These results indicate that certain highly reactive, novel mono-(meth)acrylates possess very promising potential to replace TEGDMA as reactive diluents and can readily be applied to develop superior dental resins.

Bisphenol A-Glycidyl Methacrylate↗
PubMed2005

In vitro study of antibiotic effect on bacterial adherence to acrylic intraocular lenses.

Implantation of artificial intraocular lenses into the eye during ophthalmic surgical procedures ensures an unliving surface on which bacterial pathogens may attach and form biofilms. Despite antibiotic treatment bacteria growing in biofilms might cause inflammation and serious complications. In this study the adhesive ability of 7 Staphylococcus aureus and 11 coagulase-negative Staphylococcus (CNS) strains to the surface of acrylic intraocular lenses had been examined by the ultrasonic method. In untreated cases adhesion of the S. aureus and CNS strains did not differ significantly. We could not demonstrate significant differences between the adhesive ability of the standard strains and the clinical isolates. In this study a single--60 min long--antibiotic (ciprofloxacin and tobramycin) treatment had been applied, that correlate well with the single or intermittant antibiotic prophylaxis of patients. Ciprofloxacin administration was able to reduce significantly the number of attached cells on the surface of acrylic lenses both in the case of S. aureus and CNS strains. Dependence of the effect from concentration could also be demonstrated. Tobramycin treatment was able to inhibit significantly the attachment of S. aureus cells. Despite the debate on antibiotic prophylaxis we presented in our experiments that a single antibiotic administration can decrease the attachment of bacterial cells to the surface of acrylic intraocular lenses, and might be effective in the prevention of postoperative endophthalmitis, that is a rare but serious complication of ophthalmic surgery.

Anti-Bacterial Agents↗
PubMed2006

pH-responsive polymeric micelles of poly(ethylene glycol)-b-poly(alkyl(meth)acrylate-co-methacrylic acid): influence of the copolymer composition on self-assembling properties and release of candesartan cilexetil.

The objective of the present study was to investigate the influence of chemical structure and molecular weight of pH-sensitive block copolymers on their self-assembling properties, the loading and the release of candesartan cilexetil (CDN). Block copolymers of poly(ethylene glycol) and t-butyl methacrylate, iso-butyl acrylate, n-butyl acrylate or propyl methacrylate were synthesized by atom transfer radical polymerization. pH-sensitivity was obtained by hydrolysis of t-butyl groups. The poorly water-soluble drug CDN was incorporated in the micelles and the in vitro drug release was evaluated as a function of pH. The critical aggregation concentration of hydrolyzed copolymers (pK(a)=6.2-6.6) was higher compared to the unhydrolyzed ones. Dynamic light scattering studies and atomic force microscopy images revealed uniform size micelles with aggregation numbers ranging from 60 to 160. The entrapment efficiency of CDN was generally found to be above 90%, with drug loading levels reaching approximately 20% (w/w). Differential scanning calorimetry studies showed the amorphous nature of entrapped CDN. The release of CDN from pH-sensitive micelles was triggered upon an increase in pH from 1.2 to 7.2. These findings suggest that the PEG-b-poly(alkyl(meth)acrylate-co-methacrylic acid)s can self-assemble to form micelles which exhibit high loading capacities for CDN and release the drug in a pH-dependent fashion.

Angiotensin II Type 1 Receptor Blockers↗
PubMed2005

A quantitative differentiation method for acrylic fibers by infrared spectroscopy.

Absorbance peak areas of nitrile (2240 cm(-1)), carbonyl (1730 cm(-1)) and CH (1370 cm(-1)) groups were obtained for 48 colorless acrylic fibers by infrared (IR) microspectroscopy. The carbonyl signal, related to the comonomers most commonly used in acrylic fibers, was ratioed against the nitrile and CH bands, pertaining to the backbone of the polymer chains. The ratios A1730/A2240 and A1730/A1370, a relative measure of the comonomer content in the fiber, were used to differentiate the samples. A decrease in the crystallinity of fibers has been noted with increasing comonomer content. Relative standard deviation (R.S.D.) of the ratios were 1 and 3% for repetitive analyses on the same location and along the length of the same single fiber, respectively. When different fibers of the same sample were examined, results were reproducible within 6%. This simple method can greatly enhance the evidential value of colorless acrylic fibers, being able to discriminate them and thus helping the Court to better assess their significance.

Journal Article↗
PubMed2006

Comparative elution of moxifloxacin from Norian skeletal repair system and acrylic bone cement: an in vitro study.

The objective of this study was to evaluate the efficacy of Norian skeletal repair system (SRS), a novel biodegradable and injectable form of calcium phosphate cement with a composition similar to that of cancellous bone, as a carrier for moxifloxacin, which is the most potent quinolone agent against staphylococci and Enterobacteriaceae. Norian SRS was mixed with moxifloxacin at a ratio of ca. 100:3 at room temperature and solidified in the bottom of a cylindrical vial. The same procedure was followed for acrylic bone cement. A total of five vials were prepared per system. Mueller-Hinton broth was placed over the free surface of both systems and the vials were transferred to a 37 degrees C incubator. The broth was replaced daily until visual degradation of both systems. Moxifloxacin was measured in aliquots of broth after passage through a high-performance liquid chromatography system. Optical degradation of both systems occurred after 450 days. Until Day 17, concentrations eluted from both systems were similar. After Day 18 until degradation, concentrations eluted by Norian SRS were statistically higher than those eluted by acrylic bone cement and ranged between 100 mg/L and 800 mg/L. The mean area under the concentration-time curve (AUC) over 450 days of sampling was 241 935.0 mg/L day for Norian SRS and 18 300.0 mg/L day for the acrylic bone cement system (P=0.043). Norian SRS is a novel biodegradable system providing excellent strength and mineralisation to bone. It was shown that this system allows in vitro elution of moxifloxacin at significant concentrations, making it a promising candidate for the therapy of chronic osteomyelitis.

Absorbable Implants↗
PubMed2004

Cranioplasty using acrylic material: a new technical procedure.

AIM: Today, cranioplasty is performed using different procedures. Numerous materials may be used to reconstruct the cranial vault including autologous bone and different types of synthetic resins. When plastic materials are used, the main requirement for an effective cranioplasty is the preoperative shaping of the implant to fit the bony defect precisely. In this paper, experience with a new method for cranioplasty using an acrylic cranial implant is presented. MATERIAL AND METHODS: In this new technical procedure an acrylic implant, precisely shaped to the defect, is fabricated preoperatively using CT data. The study consists of 15 cases in whom cranioplasty was performed using this method. In all these, reconstruction was at least 3 months after the initial operation that lead to the cranial bony defect. RESULTS: No major complications occurred and the final functional and aesthetic results were good in all cases. The acrylic implant manufacture does not require the use of complex computer interface software or high-tech equipment, but involves simple, cheap, repeatable processes.

Adult↗
PubMed2004

Repair of bis-acryl provisional restorations using flowable composite resin.

Provisional restorations provide interim coverage for prepared teeth while fixed definitive restorations are fabricated. Several types of autopolymerizing acrylic resins have been used for many years to fabricate provisional restorations. In recent years, bis-acryl resin composite material has gained popularity among clinicians for the direct fabrication of provisional fixed restorations. Occasionally, deficiencies may occur while fabricating a direct provisional restoration and require chairside repair. This article describes an effective procedure for the use of light-polymerized flowable composite resin for the intraoral repair of bis-acryl provisional restorations.

Cementation↗
PubMed2006

Molecular interaction studies of acrylic esters with 1-alcohols.

Hydrogen bonding between 1-alcohols and acrylic esters in n-heptane has been studied by FTIR spectroscopic method. The formation constant of the 1:1 complexes has been calculated using Nash method. The values of formation constant and free energy change vary with alcohol and ester chain length, which suggests that the strengths of the intermolecular O-H...O=C bonds are shown to be dependent on the alkyl group of acrylic esters and the 1-alcohols and the results shows that the proton donating ability of 1-alcohols is in the order: 1-propanol<1-butanol<1-pentanol and the accepting ability of acrylic esters is in the order: methyl methacrylate<ethyl methacrylate<butyl methacrylate.

1-Butanol↗
PubMed2004

Foldable acrylic versus rigid polymethylmethacrylate intraocular lens in combined phacoemulsification and trabeculectomy.

BACKGROUND: Combined trabeculectomy and phacoemulsification is a widely accepted option in treating patients with glaucoma who also have cataracts. Implantation of a foldable intraocular lens (IOL) in cataract surgery has several theoretical advantages. We performed a study to determine the results of combined phacoemulsification and trabeculectomy with mitomycin C and implantation of either a foldable acrylic or rigid polymethylmethacrylate (PMMA) IOL. METHODS: Review of the charts of 58 consecutive patients (60 eyes) who underwent combined phacotrabeculectomy for concomitant cataract and glaucoma at a university-affiliated hospital in Montreal between September 2001 and December 2002. Forty-one eyes received a foldable acrylic lens (3.2-mm-wide incision), and 19 eyes received a rigid PMMA lens (5.2-mm-wide incision). Outcome measures included visual acuity, intraocular pressure (IOP) and postoperative complications. The results in the two groups were compared. RESULTS: There were no differences in baseline characteristics between the two groups. Earlier recovery of visual acuity was noted in the foldable IOL group than in the rigid IOL group (p = 0.013 for the difference at day 7). IOP control was similar in the two groups, as was the incidence of IOP spikes in the early postoperative period. INTERPRETATION: The results suggest that combined phacotrabeculectomy with mitomycin C using a foldable acrylic IOL allows for good postoperative IOP control and earlier visual recovery than the same procedure with insertion of a rigid PMMA lens.

Aged↗
PubMed2000

Clinical and Experimental Observation of Glistening in Acrylic Intraocular Lenses.

Purpose: To study whether the glistening on implanted acrylic intraocular lenses increases or not.Method: 1. Prospective study: We studied the glistening on 49 implanted acrylic intraocular lenses, particularly the time of appearance and increase after glistening appeared. 2. Experiment: We kept an intraocular lens immersed in saline solution at 50 degrees centigrade for 2 hours and then moved this lens into saline solution at 35 degrees centigrade, and observed this lens during immersion.Results: 1. Prospective study: Glistening was present in 28 eyes (57%), and appeared from 2 to 16 months postoperatively. A few months after appearance it become stable and did not increase further. 2. Experiment: On the 10th day after observation, we could see glistening on the lenses. The points of glistening were 10 µm or less in size, and did not change during 60 days of observation.Conclusion: The glistening in acrylic intraocular lenses seemed to become stable a few months after appearance. This our experimental method is useful, because it gives us glistening similar to clinical cases in a short time.

Journal Article↗
PubMed2003

Small-angle neutron scattering study of particle coalescence and SDS desorption during film formation from carboxylated acrylic latices.

Four monodisperse core-shell latices were synthesized for small-angle neutron scattering (SANS) studies, differing by the acrylic acid content in the particle shell (1 or 4 wt%) and the T(g) of the acrylic core (around -40 or 10 degrees C). In a first part, the coalescence kinetics of the surfactant-free latices were studied. It was shown that coalescence was hindered by an increase in the acrylic acid content of the shell, pH of the latex, and Tg of the core. These results could be interpreted in terms of chain mobility in the shell and in the core. Upon coalescence, the hydrophilic phase was segregated in spherical, polydisperse domains with an average diameter of 110 nm. In a second part, labeled SDS was used to follow desorption of the surfactant during film formation. It was shown that desorption occurred early in the film formation process when the latex still contained around 20% of water. A small fraction of the surfactant remained irreversibly adsorbed at the particle surface.

Journal Article↗
PubMed1998

Repair of acrylic resin denture base reinforced with glass fiber.

STATEMENT OF PROBLEM: The ultimate goal of any denture repair is to restore the original strength of the denture and to avoid further fracture. PURPOSE: This study investigated the strength and deflection of repaired acrylic resin joints reinforced with various glass fiber concentrations. MATERIAL AND METHODS: Transverse strength, maximum deflection, and modulus of elasticity of glass fiber-reinforced polymethyl methacrylate acrylic resin were studied with a 3-point load test on 54 intact specimens. Six concentrations of type B glass fiber specimens were prepared (n = 9 per each fiber group). Fractured joint margins were rounded, a 2-mm gap was placed between them, and then they were repaired with autopolymerizing acrylic resin and retested. RESULTS: Transverse strength, maximum deflection, and the stiffness of all joints were significantly lower after the repair. Among the groups tested, the units treated with 1% glass fiber displayed the highest transverse strength before and after repair. Modulus of elasticity of the repaired 1% fiber concentration units was enhanced by approximately 25% over those repaired but untreated with glass fiber (0% fiber).

Analysis of Variance↗
PubMed2002

Study on the stabilisation of collagen with vegetable tannins in the presence of acrylic polymer.

Collagen, a unique connective tissue protein finds extensive application as biocompatible biomaterial in wound healing, as drug carriers, cosmetics, etc. A study has been undertaken to stabilise Type-I collagen of rat-tail tendon using plant polyphenol (Acacia Mollissima) in the presence of an acrylic polymer. It has been found that collagen fibres pre-treated with acrylic polymer followed by the treatment with Acacia Mollissima exhibited an increase in hydrothermal stability by 25 degrees C. Infrared spectroscopic studies display the changes in the spectral characteristics of native and treated collagen films. Transmission electron microscopic and circular dichroic studies provide an insight into the understanding of the improved stabilisation of collagen, due to treatment with acrylic polymer and plant polyphenols. The study is expected to enhance the biomaterial applications of collagen tissues.

Animals↗