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PubMed1996

Effect of folding on the optical quality of soft acrylic intraocular lenses.

PURPOSE: To assess the effect of folding procedures on modulation transfer function (MTF) and resolving power (RP) in soft acrylic intraocular lenses (IOLs). SETTING: Faculty of Engineering, Chiba University, Chiba, Japan. METHODS: Folding procedures and other manipulations were performed on +18.0 diopter soft acrylic lenses (MA60BM, AcrySof, Alcon Surgical). The IOLs were then immersed in the water chamber of a model eye and MTF and RP under veiling glare light measured. The optical surfaces of the IOLs were examined microscopically. RESULTS: After the IOLs had been folded for 30 seconds, MTF recovered 8 and 6 minutes after unfolding in 20 degrees C 37 degrees C balanced salt solution, respectively. Prolonged folding of 10, 20, and 60 minutes did not affect the final MTF, which was measured 30 minutes after unfolding. However, RP deteriorated after the 60 minute folding. Optic damage was observed after the 20 and 60 minute foldings. Neither parameter changed after the IOLs were tightly folded for 30 seconds; however, both deteriorated slightly after the IOLs were tightly folded for 5 minutes, and minor damage was seen on the optics. With fewer than 10 artificial linear cracks in the central 3 mm of the optic, MTF was not affected; with 20 or fewer, RP was not affected. After forceps pressure on the central optic, MTF recovered within 6 minutes. CONCLUSION: The optical quality of soft acrylic IOLs are not easily affected unless extreme nonphysiological manipulations are applied.

Acrylates↗
PubMed1996

Implantation of multiple foldable acrylic posterior chamber lenses in the capsular bag for high hyperopia.

This case series describes the implantation of multiple acrylic intraocular lenses (IOLs) in the capsular bag of six eyes of three highly hyperopic patients (spherical equivalent +5.75 to +8.62) during cataract surgery. Two foldable acrylic lenses were placed in the capsular bag of each eye. Preoperative best corrected visual acuity (BCVA) ranged from 20/50 to 20/300. Postoperative uncorrected visual acuity ranged from 20/25 to 20/60, while BCVA ranged from 20/25 to 20/40. Multiple acrylic lenses were used successfully in cases in which a single IOL would have given inadequate correction.

Acrylates↗
PubMedDate not supplied

Two year clinical study of a soft acrylic intraocular lens.

PURPOSE: To assess the efficacy and safety of a soft acrylic intraocular lens (IOL) in small incision cataract surgery. METHODS: Sixty-four eyes of 64 patients (mean age 71.0 +/- 7.7 [SD] years) who had phacoemulsification and implantation of a soft acrylic IOL were followed for 2 years. RESULTS: At day 1, 96.9% of patients had corrected visual acuity of 20/40 or better, and 50.0% had 20/20 or better. At 2 years postoperatively, 100% had 20/40 or better, and 86.3% had 20/20. Surgically induced keratometric cylinder remained quite stable throughout the 2 year follow-up period, with axis-based astigmatism of +/- 0.3 diopters. Flare intensity measured with the laser flare-cell meter was less than that with other type of IOLs measured, including poly(methyl methacrylate) and silicone. Neodymium:YAG laser capsulotomy was performed in seven cases (11.1%). without causing damage to the optic. No other postoperative complications were encountered. CONCLUSION: Soft acrylic IOLs have clinically apparent advantages in small incision cataract surgery.

Acrylates↗
PubMed2000

Decentration and tilt: silicone multifocal versus acrylic soft intraocular lenses.

PURPOSE: To compare differences in decentration and tilt between a silicone multifocal and an acrylic intraocular lens (IOL) by evaluating postoperative changes. SETTING: Department of Ophthalmology, College of Medicine, The Catholic University of Korea, Seoul, Korea. METHODS: Forty eyes of 20 patients with IOL implantation were randomized into 2 groups according to IOL type: 3-piece silicone multifocal IOL or 3-piece acrylic IOL. All lenses were implanted in the capsular bag through a clear corneal incision after continuous curvilinear capsulorhexis and phacoemulsification. The amount of the decentration and the degree of the tilt of each IOL were measured using the EAS-1000 anterior eye segment analysis system 1 day and 1 and 2 months after surgery. RESULTS: No significant difference in decentration and tilt was found among the 3 follow-ups or between lens types. CONCLUSION: Neither IOL decentration nor tilt showed significant progression up to 2 months in eyes with a silicone multifocal or acrylic IOL when the IOLs were placed properly in the capsular bag. The amount of decentration and tilt was similar between lens types.

Acrylic Resins↗
PubMed2003

The retention of 14C-labelled poly(acrylic acids) on gastric and oesophageal mucosa: an in vitro study.

Polymers that bind from solution onto gastric mucosa can be used either as a means of facilitating localised drug delivery, or can act as therapeutic agents in their own right (e.g. by forming a protective layer or by inhibiting enzymes). In our previous study [Int. J. Pharm. 236 (2002) 87], the binding and retention of labelled poly(acrylic acid)s on sections of gastric mucosa from pigs was evaluated using 'dynamic flow' conditions and a high molecular weight poly(acrylic acid) was found to bind most avidly. In the current study, 3% solutions of 'low', 'high' and 'ultra high' molecular weight polymers were evaluated in the 'dynamic flow' model for their ability to bind to tissues from the fundic and pyloric regions of the stomach and the oesophagus of pigs. All the polymers tested were retained on each mucosa for extended periods; the high and ultra high molecular weight polymers showed the greatest retention. Examination of the kinetics of polymer elution suggested that two fractions exist, 'bound' and 'unbound' polymer, showing differing retention profiles. The high molecular weight polymer showed the greatest retention on pyloric tissue, particularly on the upper sections. The retention of the ultra high and high molecular weight polymer was similar on the fundic and oesophageal mucosa, and the distribution was even across the tissue. It was concluded that poly(acrylic acid) binding from solution presents a therapeutic opportunity, and the differences in binding and retention of the polymers on the different mucosae could present an opportunity for targeting.

Acrylic Resins↗
PubMed1976

Mechanims of stimulation of in vitro protein synthesis by some copolymers of styrene, vinyluracil, and vinyladenine with maleic acid and acrylic acid.

Copolymers of vinyl bases with acrylic acid and styrene or 1-vinyluracil with maleic acid were found to stimulate in vitro polyphenylalanine synthesis using a system extracted from Escherichia coli MRE600. Poly(styrene-maleic acid) was found to inhibit a ribosomal bound ribonuclease. Poly(1-vinyluracil, maleic acid), poly(1-vinyluracil, acrylic acid), and poly(9-vinyladenine, acrylic acid) were not inhibitors of the ribosome bound ribonuclease. The potent (up to fivefold) stimulation by these three polymers is due to the action of the polymers to interfere with ribosomal bound inhibitory protein. A protein, removed by washing ribosomes with 1 M ammonium chloride, characterized by M.J. Miller, A. Niveleau, and A.J. Wahba ((1974) J. Biol. Chem. 249, 3803) has been described as a potent inhibitor of in vitro poly(U)-coded protein synthesis using extracts of Escherichia coli MRE 600.

Acrylates↗
PubMedDate not supplied

Graft copolymerization of ethyl acrylate onto cellulose using ceric ammonium nitrate as initiator in aqueous medium.

Ceric ammonium nitrate (CAN) in the presence of nitric acid has been used as efficient initiator for graft copolymerization of the ethyl acrylate onto cellulose at 35.0 +/- 0.1 degrees C. Graft copolymerization of ethyl acrylate onto cellulose has taken place through the radical initiation process. The graft yield and other grafting parameters have been evaluated by varying concentration of ethyl acrylate from 2.5 x 10(-1) to 15.0 x 10(-1) mol dm(-3) and ceric ammonium nitrate from 5.0 x 10(-3) to 25.0 x 10(-3) mol dm(-3) at constant concentration of the nitric acid (8.0 x 10(-2) mol dm(-3)). The rate of graft copolymerization has shown 1.5 order with respect to the concentration of the ceric ammonium nitrate. The graft copolymerization data obtained at different temperatures were used to calculate the energy of activation, which has been found to be 28.9 kJ mol(-1) within the temperature range from 20 to 50 degrees C. The effect of addition of cationic and anionic surfactants on graft copolymerization has also been studied. On the basis of the experimental observations, reaction steps have been proposed and a suitable rate expression for graft copolymerization has been derived.

Acrylates↗
PubMedDate not supplied

Synthesis and characterization of injectable poly(N-isopropylacrylamide-co-acrylic acid) hydrogels with proteolytically degradable cross-links.

Hydrogels composed of N-isopropylacrylamide (NIPAAm) and acrylic acid (AAc) were prepared by redox polymerization with peptide cross-linkers to create an artificial extracellular matrix (ECM) amenable for testing hypotheses regarding cell proliferation and migration in three dimensions. Peptide degradable cross-linkers were synthesized by the acrylation of the amine groups of glutamine and lysine residues within peptide sequences potentially cleavable by matrix metalloproteinases synthesized by mammalian cells (e.g., osteoblasts). With the peptide cross-linker, loosely cross-linked poly(N-isopropylacrylamide-co-acrylic acid) [P(NIPAAm-co-AAc)] hydrogels were prepared, and their phase transition behavior, lower critical solution temperature (LCST), water content, and enzymatic degradation properties were investigated. The peptide-cross-linked P(NIPAAm-co-AAc) hydrogels were pliable and fluidlike at room temperature and could be injected through a small-diameter aperture. The LCST of peptide-cross-linked hydrogel was influenced by the monomer ratio of NIPAAm/AAc but not by cross-linking density within the polymer network. A peptide-cross-linked hydrogel with a 97/3 molar ratio of NIPAAm/AAc exhibited a LCST of approximately 34.5 degrees C. Swelling was influenced by NIPAAm/AAc monomer ratio, cross-linking density, and swelling media; however, all hydrogels maintained more than 90% water even at 37 degrees C. In enzymatic degradation studies, breakdown of the peptide-cross-linked P(NIPAAm-co-AAc) hydrogels was dependent on both the concentration of collagenase and the cross-linking density. These results suggest that peptide-cross-linked P(NIPAAm-co-AAc) hydrogels can be tailored to create environmentally-responsive artificial extracellular matrixes that are degraded by proteases.

Acrylamides↗
PubMedDate not supplied

Design and properties of novel self-curing acrylic formulations for application in intervertebral disks restoration.

Novel acrylic formulations incorporating an amphiphilic macromonomer, Triton methacrylate MT, have been prepared to be applied in intervertebral disks (IVD) restoration processes. The solid phase of the formulations is composed of poly (methyl methacrylate), PMMA, incorporating in some cases chondroitin sulfate, CS, as a regenerative bioactive molecule, whereas the liquid phase is constituted by MT and 2-hydroxyethyl methacrylate, HEMA, and in some formulations acrylic acid, AA, was also added. These are prepared similarly to acrylic bone cement formulations. The obtained curing parameters, with maximum temperatures in the range of 41-72 degrees C, make them suitable to be applied as injectable systems. Glass transition temperatures and swelling degree have also been determined. Mechanical properties such as compressive, stress relaxation, and shear tests have been analyzed for all of the prepared IVD formulations exhibiting shape memory characteristics and a pronounced elastic behavior that make them as excellent candidates for the intervertebral application.

Acrylates↗
PubMed2000

Poly(N-acryl amino acids): a new class of biologically active polyanions.

Poly(N-acryl amino acids) bearing side groups with a lipophilic character or having charged functional groups (i.e. -NH(2), -COOH, -SH, -OH, and phenols) were synthesized from the radical polymerization of N-acryl amino acid monomers. Monomers were prepared from the reaction of acryloyl chloride and amino acid esters in dry solvents. Polymers of a broad molecular weight ranging from 3 000 to 60 000 Da were obtained. The polymers were optically active, and their structures were confirmed by (1)H NMR and IR spectra and elemental analysis. Hydroxyl-containing polymers were sulfated in high conversion yields by SO(3)/pyridine complex. The newly synthesized linear homopolyanions were tested for heparin-like activities: (i) inhibition of heparanase enzyme, (ii) release of basic fibroblast growth factor (bFGF) from the extracellular matrix (ECM), and (iii) inhibition of smooth muscle cell (SMC) proliferation. Polymers based on tyrosine and leucine were highly active in all three tests (microgram level). Polymers based on phenylalanine, tert-leucine, and proline were active as heparanase inhibitors and FGF release, and polymers of trans-hydroxyproline, glycine, and serine were active only as heparanase inhibitors. The polymer of cis-hydroxyproline was inactive. It was found that a net anionic charge (i.e. carboxylic acid) is essential for biological activity. Thus, methyl ester derivatives of the active polymers, zwitterionic amino acid dependent groups (lysine, histidine), and decarboxylated amino acids (tyramine, ethanolamine) were inactive. The above active polymers did not exhibit anticoagulation activity which is considered the main limitation of heparin and heparinomimetics for clinical use. These synthetic poly(N-acryl amino acids) may have potential use in the inhibition of heparanase-mediated degradation of basement membranes associated with tumor metastasis, inflammation, and autoimmunity.

Acrylic Resins↗
PubMed1992

Imidazole-5-acrylic acids: potent nonpeptide angiotensin II receptor antagonists designed using a novel peptide pharmacophore model.

A series of novel nonpeptide angiotensin II receptor antagonists containing a substituted (E)-acrylic acid has been developed. The overlay of 1, an imidazole-5-acetic acid found in the patent literature, on a novel pharmacophore model of AII suggested that extension of the acid side chain and attachment of a second aryl residue to mimic the C-terminal phenylalanine region of AII would lead to increased activity. A study of extended acid side chains at C-5 of the imidazole nucleus led to the discovery of the (E)-acrylic acid 5 as a promising starting point for further exploration. As predicted by the modeling, substitution of a benzyl group on the acrylic acid side chain to mimic the phenylalanine gave increased potency. An extensive study of the SAR of the newly introduced aromatic ring revealed that electron-rich heteroaryl rings provided improved activity, most notably in the in vivo rat models. Compound 40, (E)-3-[2-butyl-1- [(2-chlorophenyl)methyl]imidazol-5-yl]-2-[(2-thienyl)methyl]-2- propenoic acid, has been shown to be a potent, competitive, and orally active small molecule AT-1 receptor antagonist. It exhibits a 2 orders of magnitude increase in binding affinity and a 10-fold improvement in in vivo potency as compared to compound 1 and represents an important milestone in the development of even more potent nonpeptide angiotensin II receptor antagonists.

Acrylates↗
PubMed1977

Polynucleotide analogues. Copolymers of vinyl bases with acrylic acid, methylacrylic acid, acrylamide, and 1-vinylpyrrolidone.

Preliminary studies are reported on the synthesis and testing of substituted vinyl polymers that are designed to have sequence specific affinity for polyribonucleic acids. Copolymers of 1-vinyluracil with acrylic acid, 2-methylacrylic acid, or 1-vinyl-2-pyrrolidone were prepared by gamma-irradiation to give the respective polymers 1,3, and 4. Similarly, 9-vinyladenine yielded copolymeric products 5 and 6 with acrylic acid or 2-methylacrylic acid. Radical initiated polymerization of 9-vinyladenine with acrylamide yielded copolymer 7. The products were characterized by elemental analysis and ultraviolet, infrared, and nuclear magnetic resonance spectroscopy. No hypochromicity could be detected on mixing polymers 1-4 with poly(adenylic acid). The acrylic acid copolymer 2 containing a high ratio of vinyluracil was a potent inhibitor of poly(adenylic acid) coded polylysine synthesis in an in vitro system. Polymers 6 and 7, containing a high proportion of vinyladenine, inhibited poly(uridylic acid) coded poly(phenylalanine) synthesis.

Acrylamides↗
PubMed2002

Facile synthesis of alpha-substituted acrylate esters.

Treatment of 5-monosubstituted Meldrum's acids with dimethylmethyleneimmonium iodide (Eschenmoser's iodide salt) in methanol gives alpha-substituted acrylate methyl esters in good yields. Easy access to 5-monosubstituted Meldrum's acids allowed us to synthesize a wide variety of alpha-substituted acrylate methyl esters. The reaction conditions are mild and tolerate many functional groups commonly used in organic synthesis; thus, this new method has potential as an alternative to conventional preparative methods for alpha-substituted acrylate esters.

Acrylates↗
PubMed2004

Flexural properties of crosslinked and oligomer-modified glass-fibre reinforced acrylic bone cement.

The flexural properties of oligomer-modified bone cement with various quantities of crosslinking monomer with or without glass fibre reinforcement were studied. The flexural strength and modulus of acrylic bone cement-based test specimens (N=6), including crosslinked and oligomer-modified structures with or without glass fibres, were measured in dry conditions and after immersion in simulated body fluid (SBF) for seven days (analysis with ANOVA). One test specimen from the acrylic bone cement group containing 30 wt % crosslinking monomer of its total monomer content was examined with scanning electron microscope (SEM) to evaluate signs of the semi-interpenetrating polymer network (semi-IPN). The highest dry mean flexural strength (130 MPa) was achieved with the bone cement/crosslinking monomer/glass fibre combination containing 5 wt % crosslinking monomer of its monomer content. The highest flexural modulus (11.5 GPa) was achieved with the bone cement/crosslinking monomer/glass fibre combination containing 30 wt % crosslinking monomer of its monomer content. SBF storage decreased the flexural properties of the test specimens, as did the addition of the oligomer filler. Nevertheless, the addition of crosslinking monomer and chopped glass fibres improves considerably the mechanical properties of oligomer-modified (i.e. porosity-producing filler containing) acrylic bone cement. In addition, some signs of the semi-IPN structure were observed by SEM examination.

Acrylic Resins↗
PubMed2005

A prospective study of the short-term treatment effects of the acrylic-splint rapid maxillary expander combined with the lower Schwarz appliance.

This prospective clinical study evaluated the short-term treatment effects of acrylic-splint rapid maxillary expander in conjunction with lower Schwarz appliance (RME-Sz) therapy to the acrylic-splint rapid maxillary expansion alone (RME-only group). Pretreatment and posttreatment lateral cephalograms were analyzed for 25 RME patients and 19 RME-Sz patients. The average time between films ranged between nine and 12 months. Statistical comparisons of the treatment changes in the RME-only and RME-Sz groups were performed by means of independent sample t-tests (P < .05). The largest difference between the two groups was in lower anterior facial height (LAFH). The normally occurring increase in LAFH was not observed in the RME-only group during the treatment period, indicating that the acrylic-splint expander had a posterior "bite block effect" on the developing craniofacial complex. LAFH increased by 1.7 mm in the RME-Sz group, a value similar to that observed in untreated individuals. Slight forward displacement of the maxilla was observed when RME was used alone, and the sagittal position of the maxilla remained unchanged in the RME-Sz group. A significant amount of intrusion of the maxillary molars (-0.8 mm) was noted in the RME-only group, whereas the maxillary molars were prevented from erupting in the RME-Sz group. The lower dentition showed a significantly greater amount of extrusion in the RME-Sz group than in the RME-only group. Finally, the Sz appliance prevented the mesial movement of the lower molars during the treatment period.

Acrylic Resins↗
PubMed2001

Microwave-cured acrylic resins and silicone-gypsum moulding technique.

This study evaluated the residual monomer (RM), Knoop hardness (KHN) and transverse strength (TS) of two microwave-cured acrylic resins (Acron MC(R) (A), GC Dent. Ind. Corp., Tokyo, Japan and Onda Cryl (O), AO Classico Ltda, São Paulo, Brazil) when processed with an all-type III gypsum moulding technique (G) or a silicone-gypsum moulding technique (S). One hundred and forty four specimens were fabricated and equally distributed into four groups (AG, AS, OG and OS). The TS tests were conducted after 48 h of water storage, and KHN values were obtained after 24, 48, 72 h and 30 days. The RM was determined every 24 or 48 h over a period of 288 h. The acrylic resins were prepared and processed according to the manufacturer's directions. Both AS and OS showed the highest means (P < 0.05) for RM (microg cm-2) only after 24 h (AS = 56.84 +/- 27.39/AG = 7.51 +/- 5.75/OS = 3.59 +/- 1.60/OG = 1.02 +/- 0.3), 48 h (AS = 28.99 +/- 9.35/AG = 2.65 +/- 2.17/OS = 2.37 +/- 0.84/OG = 0.68 +/- 0.49) and 72 h (AS = 15.98 +/- 9.01/AG = 1.40 +/- 0.57/OS = 1.87 +/- 0.52/OG = 0.75 +/- 0.44). Both AS and OS showed the highest means (P < 0.02) for KH after 24 h (AS = 18.69 +/- 2.3/AG = 17.79 +/- 0.7/OS = 18.41 +/- 1.0/OG = 16.04 +/- 0.6). After 48 h the mean values for OS and OG differed significantly (P < 0.03) (OS = 18.67 +/- 0.8/OG = 16.75 +/- 0.8). No differences of KHN were found among the groups during the storage periods. The TS values for A and O were not affected by either G or S (P > 0.05). Silicone-gypsum mould technique affected the RM and KHN of the resins in the first 2 and 5 days of analysis, respectively. The type of mould did not affect TS, and the acrylic resins differed from each other for all properties regardless of the type of mould.

Acrylic Resins↗
PubMed2001

The effect of the addition of surface treated chopped and continuous poly (methyl methacrylate) fibres on some properties of acrylic resin.

Poly (methyl methacrylate), the material most commonly used in the construction of dentures, is not without limitations particularly in terms of mechanical strength, such as flexural and fatigue strength. The Dental Practice Board for England statistics show that many dentures fail as a result of fracture. This study investigated the self-reinforcement of acrylic resin through the addition of surface treated poly (methyl methacrylate) fibres in chopped and continuous form. The effect of the addition of fibres on transverse and impact strengths was investigated. The addition of surface treated chopped or continuous fibres to acrylic resin did not improve the transverse or impact strengths. The addition of surface treated poly (methyl methacrylate), in the present form, to acrylic resin cannot be recommended as a method of reinforcement.

Acrylic Resins↗
PubMed2002

An investigation into the transverse and impact strength of "high strength" denture base acrylic resins.

A range of materials, often marketed as high strength resins is available. These materials are often expensive options to conventional heat-cured acrylic resin. The aim of this study was to investigate transverse and impact strength of five "high strength" acrylic resin denture base materials. A conventional heat-cured acrylic resin was used as a control. Specimens were prepared as specified in the International Standard Organization (ISO 1567: 1988) and British standards for the Testing of Denture Base Resins (BS 2487: 1989) and the British Standard Specification for Orthodontic resins (BS 6747: 1987) for transverse bend and impact testing. The impact strength was measured using a Zwick pendulum impact tester and the transverse bend strength measured using a Lloyds Instruments testing machine. The results showed that Metrocryl Hi, Luctitone 199 and N.D.S. Hi all had an impact strength which was significantly higher than the control. For the modulus of rupture, there was a significant difference between Sledgehammer and the other groups. There was no significant difference between the other groups and the control. For the modulus of elasticity, Sledgehammer produced the highest value followed by the control. The remaining four materials had a modulus of elasticity less than the control.

Acrylic Resins↗