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PubMedDate not supplied

Bond strength of six soft denture liners processed against polymerized and unpolymerized poly(methyl methacrylate).

The bond strength of six commercial soft denture liners was evaluated by a two-phase tensile test. The soft denture liners investigated were VinaSoft, Prolastic, Flexor, Molloplast-B, Novus, and SuperSoft. The samples were fabricated by processing them (1) against polymerized poly(methyl methacrylate), and (2) against unpolymerized poly(methyl methacrylate). The soft denture liners were processed according to the manufacturers recommendations. The samples were tested using an Instron Universal Testing Machine. The mode of failure, adhesive or cohesive, was also recorded. The bond strength when processed against unpolymerized poly(methyl methacrylate) ranged from 0.48 to 2.60 MPa, and when processed against polymerized poly(methyl methacrylate) the bond strength ranged from 0.94 to 2.56 MPa. A two-way analysis of variance (P = .05) revealed a significant increase in bond strength when the liners were processed against polymerized poly(methyl methacrylate), except for Novus, which had no change, and VinaSoft, which decreased. The Tukey interval between materials was .22 and between methods of polymerization was .08. Four of the six liners investigated demonstrated increased bond strength when processed against polymerized poly(methyl methacrylate). It was concluded that bonding can be influenced by the processing method.

Acrylic Resins↗
PubMed2001

Osteoblast cell death on methacrylate polymers involves apoptosis.

The success of an implant depends on the implant-tissue interface. There are many causes of implant failure, one of which is tissue necrosis. The aim of this in vitro study was to determine whether cell death of primary human osteoblasts (implant site specific cells) occurred by apoptosis (a form of programmed cell death) on two methacrylate polymers. Cells were cultured on poly(ethyl methacrylate)/tetrahydrofurfuryl methacrylate and poly(methyl methacrylate in the form of 13-mm discs, in conditioned medium containing leachable monomer and in the presence of various concentrations of monomer itself in the culture medium. It was found that monomer and leached monomer caused apoptosis of human osteoblast cells in this system. Tetrahydrofurfuryl methacrylate monomer was found to be more toxic than currently used monomer methylmethacrylate. Preincubation of polymers in serum containing medium was found to increase the biocompatibility of the polymers. High levels of apoptosis occurred on polymer used directly after polymerization. Apoptosis levels were decreased after polymer was incubated at 60 degrees C overnight or for 3 days. Apoptosis therefore may occur in cells at the implant site in vivo.

Apoptosis↗
PubMed2002

The effect of two polishing pastes on the surface roughness of bis-acryl composite and methacrylate-based resins.

STATEMENT OF PROBLEM: A highly polished restoration surface is necessary to promote a plaque-free environment. PURPOSE: The purpose of this study was to compare the surface roughness of 3 different bis-acryl composite-based and 3 different methyl methacrylate-based provisional crown and fixed partial denture resins after being polished with aluminum oxide and diamond paste. MATERIAL AND METHODS: Six different materials were used (Iso-Temp, Protemp II, Structer 2, Dentalon Plus, Tab 2000 Kerr, Temdent). A total of 180 specimens were fabricated: 30 specimens of each material using circular stainless steel molds 10 mm in diameter and 2 mm high. Each material was mixed and polymerized according to manufacturer's instructions. The bis-acryl composite specimens were polymerized with a laboratory light-initiating unit for 30 seconds on each side (400 to 525 nm, 75 W quartz-halogen light source). All specimens were kept in a water bath at 37 degrees C for 45 minutes. Ten specimens of each group were left as untreated controls, 10 specimens of each group were polished with the aluminum oxide paste (Composite Polish), and 10 specimens of each group were polished with the diamond paste (Insta glaze). Surface roughness was determined with a profilometer. The data were analyzed with one-way analysis of variance (Post Hoc Scheffe's S test) (P<.001). In addition, the profilometric evaluations photographic images were recorded with a scanning electron microscope to examine the surface roughness after polishing. RESULTS: The mean of the surface characteristics of the bis-acryl composites were 1.33 microm for aluminum oxide and 0.90 microm for diamond polishing paste; the mean of the results of the methyl methacrylate resins were 1 microm for aluminum oxide and 0.50 microm for diamond polishing paste. The difference between the mean values of bis-acryl resins groups and methacrylate-based resin groups were significant (P<.001). The difference between the subgroups of bis-acryl resins group (Iso-Temp, Protemp II, Structer 2) were not significant (P>.05). The difference between the subgroups of methacrylate-based resin group (Dentalon, Tab 2000, Temdent) were not significant (P>.05). CONCLUSION: Within the limitations of this study, single-phase polishing of the bis-acryl composites tested and the methacrylate resins tested with diamond-based paste produced a smoother surface than when polished with aluminum oxide paste.

Acrylic Resins↗
PubMed2000

Field amplified stacking injection--capillary electrophoresis for quantitative analysis of released methacrylic acid from dental composites.

Field-amplified stacking injection-capillary electrophoresis (FASI-CE) applied for the first time to the study of dental materials is demonstrated in this report. CE was used to separate methacrylic acid from the other degraded components. Due to the background electrolyte being weakly basic and methacrylic acid being negatively charged, in-capillary enrichment of the analyte was achieved by FASI. A detection limit of less than 50 ppb was obtained with good reproducibility (relative standard deviation < 3%). The method was applied to the analysis of four commercially available dental composites. Results showed that FASI-CE was effective in monitoring the fabrication process and product quality of restorative materials fabricated from methacrylate-based composites by analyzing the amount of methacrylic acid released from the residual methacrylate monomers.

Composite Resins↗
PubMedDate not supplied

High performance liquid chromatographic determination of methacrylate in blood serum.

Methacrylic acid is a hydrolytic breakdown product of methylmethacrylate which is widely used in orthopaedic surgery, dentistry and in the chemical industry for fabrication of acrylic resins. Information on the toxicity of methacrylic acid and its metabolism is limited. To facilitate studies in this field we developed a liquid chromatographic procedure allowing determination of methacrylate in blood serum. The procedure was based on reversed-phase HPLC using a gradient elution with UV detection at 210 or 240 nm. The method was linear up to 5 mM concentration with a detection limit of 0.5 microM. The procedure was applied to determination of methacrylate in rat blood serum after administration of sodium methacrylate solution into the stomach. A peak of this compound was demonstrated in the chromatogram 10 min after administration which disappeared after 60 min, confirming suitability of the method for biological applications.

Animals↗
PubMed2005

Nanomechanical properties of self-reinforced composite poly(methyl methacrylate) as a function of processing temperature.

Understanding the wear characteristics of bone cement and its alternatives is critical to improving the quality and longevity of hip replacements. A novel composite material, self-reinforced composite poly(methyl methacrylate), has been previously developed for potential use as a pre-coat material for hip implants. The goal of this work was to examine the properties of self-reinforced composite poly(methyl methacrylate) as a function of processing temperature. Nanoindentation tests were performed to measure hardness and modulus of self-reinforced composite poly(methyl methacrylate) at the nanoscale. Nanoscratch tests were performed parallel, orthogonal, and longitudinal to composite fibers to measure residual scratch depths. Significant differences were found in the hardness, modulus, and residual scratch depth as a function of processing temperature when compared to poly(methyl methacrylate). As processing temperature is increased, hardness decreased and residual scratch depths increased. Data also showed that fiber orientation plays a critical role in scratch resistance. Scratching orthogonal to fiber orientation produced the least residual scratch depth ranging from 524 nm at 105 degrees C to 838 nm at 150 degrees C, compared to a residual scratch depth for poly(methyl methacrylate) of 842 nm.

Hot Temperature↗
PubMed2001

Investigation of infrared calibration methods for application to the study of methyl methacrylate polymerization.

Infrared spectroscopy has been used to monitor the polymerization of methyl methacrylate. Concentrations of methyl methacrylate in the reaction mixture were determined by use of three calibration methods. Classical quantitative analysis was used to measure the height of the stretching vibration bands of the vinyl group at 1639 cm(-1). A calibration procedure using the considerably higher intensity of the C = O stretching vibration band of the carbonyl ester group at 1725 cm(-1) seemed useful only for high concentrations of methyl methacrylate, i.e. at the beginning of reaction, because this band overlaps that of poly(methyl methacrylate). Use of second-derivative spectra and measuring their values at 1725 cm(-1) enabled estimation of ten times lower concentrations of methyl methacrylate the calibration using the band from the vinyl group.

Calibration↗
PubMed1987

Adhesion of cultured human endothelial cells onto methacrylate polymers with varying surface wettability and charge.

The adhesion of human endothelial cells (HEC) onto a series of well-characterized methacrylate polymer surfaces with varying wettabilities and surface charges was studied either in serum-containing (CMS) or in serum-free (CM) culture medium. HEC adhesion in CMS onto (co)polymers of hydroxyethyl methacrylate (HEMA) and methyl methacrylate (MMA) was found to be optimal on the moderately wettable copolymer (mol ratio 25 HEMA/75 MMA). Positively-charged copolymers of HEMA or MMA with trimethylaminoethyl methacrylate-HCl salt (TMAEMA-Cl), both with mol ratios of 85/15 and a negatively-charged copolymer of MMA with methacrylic acid (MAA), mol ratio 85/15, showed high numbers of adhering HEC. In CM, HEC adhered onto the three charged copolymers mentioned above, but neither onto the copolymer of HEMA and MAA (mol ratio 85/15) nor onto the HEMA/MMA co- and homopolymers. Complete cell spreading in CM was only observed on the positively-charged copolymers.

Acrylates↗
PubMed1990

Glycidyl methacrylate-styrene copolymer latex particles for immunologic agglutination tests.

New latex particles for immunologic agglutination reaction were prepared by a seeded polymerization technique for the emulsifier-free copolymerization of styrene and glycidyl methacrylate. The surface of the latex particles was presumed to be dotted with hydrophilic domains, giving stability to the particles. The remaining areas, to which many antigens or antibodies were strongly adsorbed, were hydrophobic. Various groups of the glycidyl methacrylate-styrene latex particles were coated with human immunoglobulin G, and immunologic agglutinating potencies were compared by the box-titration method. Immunologic reactivities of the latex particles decreased with an increase of glycidyl methacrylate content at concentrations of 1 mol% or higher. Latex particles containing 0.5 to 0.75 mol% GMA caused strong immunologic agglutination besides showing good stability, indicating the availability of these latex particles. Glycidyl methacrylate-free polystyrene latex particles caused non-specific agglutination, while the immunologic agglutinating ability of glycidyl methacrylate-styrene latex particles, prepared by the unseeded polymerization technique was weak.

Acrylates↗
PubMed1991

Adhesion of Escherichia coli on to a series of poly(methacrylates) differing in charge and hydrophobicity.

The adhesion of three Escherichia coli strains on to six poly(methacrylates) differing in hydrophobicity and surface charge was measured as a function of time under laminar flow conditions. Polymers used were poly(methyl methacrylate) (PMMA), poly(hydroxyethyl methacrylate) (PHEMA) and copolymers of MMA or HEMA with either 15% methacrylic acid (MAA) or 15% trimethylaminoethyl methacrylate-HCl salt (TMAEMA-Cl). Bacterial and polymer surfaces were characterized by means of water contact angles and zeta potentials. Both the sessile drop contact angles and the zeta potentials of the bacterial surfaces were significantly different. No significant differences in the sessile drop contact angles of the polymer surfaces were observed. Using the Wilhelmy plate technique large contact angle hysteresis was observed for the different polymer surfaces. Surfaces of copolymers with MAA had more negative zeta potentials than those of the corresponding homopolymers. Surfaces of copolymers with TMAEMA-Cl had positive zeta potentials. The highest numbers of adherent bacteria were found on materials with positive zeta potentials, irrespective of the bacterial strain used. Bacterial adhesion on to copolymers with MAA was less than on to the corresponding homopolymers. Bacterial equilibrium adhesion values correlate with the zeta potentials of the polymer surfaces (r greater than 0.85). On substrates with less negative zeta potentials high numbers of adhered bacteria were observed. Additionally, the equilibrium bacterial adhesion values could be related with receding contact angles of polymer surfaces with negative zeta potentials (r greater than 0.86). High equilibrium adhesion values were obtained for polymers with high contact angles. No correlation between the zeta potentials and contact angles of the bacteria with the adhesion values was found.

Bacterial Adhesion↗
PubMed1991

Heterocyclic methacrylates for clinical applications. III. Water absorption characteristics.

The water absorption and desorption behaviour of poly(isobornyl methacrylate) and poly(tetrahydropyran-2-ylmethyl methacrylate) obeyed diffusion laws on repeated absorption/desorption cycles. However, the polymers of 2,3-epoxypropyl, tetrahydrofurfuryl and tetrahydropyranyl methacrylates did not obey diffusion laws, did not equilibrate after 2 yr immersion in water and exhibited very high uptake values (30-90%). For 2,3-epoxypropyl methacrylate, the sample disintegrated. A clearly detailed structure of the heterocyclic ring is critical. The use of these monomers in room temperature polymerizing poly(ethyl methacrylate)/monomer systems generally reflected the behaviour of the related homopolymers.

Absorption↗
PubMed1993

Polymerization contraction and conversion of light-curing BisGMA-based methacrylate resins.

The aim of this study was to investigate the polymerization contraction and the conversion of light-curing methacrylate resins based on bisphenol-A bis(2-hydroxypropyl)methacrylate (BisGMA) diluted with triethylene glycol dimethyacrylate (TEGDMA), methyl methacrylate (MMA), hydroxypropyl methacrylate (HPMA) or (+/-)-2-ethylhexyl methacrylate (EHMA). The contraction measurements were carried out with a linometer, a simple device to determine true linear polymerization contraction of liquid monomers at ambient temperature. The contraction increased with the amount of diluting monomer. The estimated conversion of the BisGMA-TEGDMA, calculated using the contraction, is consistent with literature values. The BisGMA-HPMA mixtures showed high conversions at moderate contraction.

Composite Resins↗
PubMed2004

Residual methyl methacrylate monomer, water sorption, and water solubility of hypoallergenic denture base materials.

STATEMENT OF PROBLEM: Denture base materials have the potential to cause irritation and allergic reaction to the oral mucosa. Water sorption and water solubility of denture base resins affect dimensional behavior and denture stability. A correlation between residual monomer and water sorption exists. PURPOSE: This in vitro study compared the amount of residual monomer, quantity of water sorption, and solubility of 4 denture base materials purported to be hypoallergenic with those of a polymethyl methacrylate-based (PMMA) heat-polymerizing acrylic resin. MATERIAL AND METHODS: The denture base resins Sinomer (heat-polymerized, modified methacrylate), Polyan (thermoplastic, modified methacrylate), Promysan (thermoplastic, enterephthalate-based), and Microbase (microwave polymerized, polyurethane-based), which are purported to be hypoallergenic, and Paladon 65 (heat-polymerized, methacrylate, control group) were examined. Specimens of each material were tested for residual methyl methacrylate (MMA) monomer (% wt, n=3), amount of water sorption (microg/mm3, n=5) and water solubility (microg/mm3, n=5), according to ISO 1567:2000. The residual MMA monomer concentrations were determined by gas chromatography (GC). The data were analyzed with 1-way ANOVA and the Bonferroni-Dunn multiple comparisons post hoc analysis for each test variable (alpha=.05). RESULTS: Significantly lower residual MMA monomer was shown for Sinomer and Polyan compared to the PMMA control group (0.90 +/- 0.20% wt, P<.05). Sinomer contained 0.31% +/- 0.00% wt MMA monomer, and Polyan exhibited residual MMA monomer content of 0.44% +/- 0.01% wt. Promysan and Microbase did not contain detectable residual MMA. Water sorption of Promysan (16.21 +/- 0.96 microg/mm3) was significantly lower than Paladon 65 (23.04 +/- 3.13 microg/mm3, P<.0001), whereas water solubility of the hypoallergenic denture base materials (0.34-0.84 +/- 0.05-0.09 microg/mm3) was not significantly lower than the PMMA material (0.40 +/- 0.06 microg/mm3, P>.05). Except for Sinomer, the tested denture base resins passed the requirements of ISO 1567 regarding residual MMA monomer (<2.2% wt). Sinomer failed to comply with the requirements for residual MMA monomer because the manufacturer claimed that the material did not contain any MMA. The tested denture base materials fulfilled the requirements regarding water sorption (<32 microg/mm3) and solubility (<1.6 microg/mm3). CONCLUSION: The tested hypoallergenic denture base materials exhibited significantly lower residual monomer content than PMMA. Promysan and Microbase showed no detectable residual MMA.

Absorption↗
PubMed2006

Synthesis, swelling behavior, and biocompatibility of novel physically cross-linked polyurethane-block-poly(glycerol methacrylate) hydrogels.

Physically cross-linked novel block copolymer hydrogels with tunable hydrophilic properties for biomedical applications were synthesized by controlled radical polymerization of polyurethane macroiniferter and (2,2-dimethyl-1,3-dioxolane) methyl methacrylate. The block copolymers were converted to hydrogels by the selective hydrolysis of poly[(2,2-dimethyl-1,3-dioxolane) methyl methacrylate] block to poly(glycerol methacrylate). The block copolymerization has been monitored by monomer conversion and molecular weight increase as a function of time. It was observed that the polymerization proceeded with a characteristic "living" behavior where both monomer conversion and molecular weight increased linearly, with increasing reaction time. The resulting hydrogels were investigated for their equilibrium water content (EWC), dynamic water contact angles, swelling kinetics, thermodynamic interaction parameters, plasma protein adsorption, and platelet adhesion. Similar to our previous mechanically responsive hydrogels (Mequanint, K.; Sheardown, H. J. Biomater. Sci. Polym. Ed. 2005, 10, 1303-1318), the present results indicated that block copolymer hydrogels have excellent hydrophilicity and swelling behavior with improved modulus of elasticity. The equilibrium swelling was affected by the hydrolysis time, block length of poly(glycerol methacrylate), temperature, and the presence of soluble salts. Fibrinogen adsorption and platelet adhesion were significantly lower for the hydrogels than for the control polyurethane, whereas albumin adsorption increased for the hydrogels in proportion to the contents of poly(glycerol methacrylate). These hydrogels have potential in a number of biomedical applications such as drug delivery and scaffolds for tissue engineering.

Adsorption↗
PubMed1997

Degradation kinetics of methacrylated dextrans in aqueous solution.

The kinetics of the hydrolysis of glycidyl methacrylate derivatized dextran (dex-MA), hydroxyethyl methacrylate derivatized dextran (dex-Hema, and hydroxyethyl methacrylate (HEMA) were systematically investigated in aqueous solution in the H0/pH range of -1.8 to 10.4 at 37 degrees C. The degradation products were quantified with reversed-phase HPLC and used to calculate the residual amount of dextran-bound methacrylate esters. In all compounds the degradation reactions follow first-order kinetics, the rate constants being susceptible to both specific acid and specific base catalysis. The reaction rate constant was independent of both the dex-MA concentration and the degree of substitution. The log Kobs-pH profiles can be divided into three parts: a proton-catalyzed, a solvent-catalyzed, and a hydroxyl-catalyzed section. At high acidities, dex-HEMA and HEMA are equally stable, but about seven times less stable than dex-MA. At alkaline pH, the order of stability is HEMA > dex-MA > dex-HEMA. This demonstrates that at alkaline pH dex-HEMA is predominantly degraded by hydrolysis of the carbonate ester, whereas at low pH, hydrolysis of the methacrylate ester is the main degradation route of this compound.

Buffers↗
PubMed2004

Synthesis and characterization of novel pH-responsive microgels based on tertiary amine methacrylates.

Emulsion polymerization of 2-(diethylamino)ethyl methacrylate (DEA) in the presence of a bifunctional cross-linker at pH 8-9 afforded novel pH-responsive microgels of 250-700 nm diameter. Both batch and semicontinuous syntheses were explored using thermal and redox initiators. Various strategies were evaluated for achieving colloidal stability, including charge stabilization, surfactant stabilization, and steric stabilization. The latter proved to be the most convenient and effective, and three types of well-defined reactive macromonomers were examined, namely, monomethoxy-capped poly(ethylene glycol) methacrylate (PEGMA), styrene-capped poly[2-(dimethylamino)ethyl methacrylate] (PDMA50-St), and partially quaternized styrene-capped poly[2-(dimethylamino)ethyl methacrylate] (10qPDMA50-St). The resulting microgels were pH-responsive, as expected. Dynamic light scattering and 1H NMR studies confirmed that reversible swelling occurred at low pH due to protonation of the tertiary amine groups on the DEA residues. The critical pH for this latex-to-microgel transition was around pH 6.5-7.0, which corresponds approximately to the known pKa of 7.0-7.3 for linear PDEA homopolymer. The microgel particles were further characterized by electron microscopy and aqueous electrophoresis studies. Their swelling and deswelling kinetics were investigated by turbidimetry. The PDEA-based microgels were compared to poly[2-(diisopropylamino)ethyl methacrylate] (PDPA) microgels prepared with identical macromonomer stabilizers. These PDPA-based microgels had a lower critical swelling pH of around pH 5.0-5.5, which correlates with the lower pKa of PDPA homopolymer. In addition, the kinetics of swelling for the PDPA microgels was somewhat slower than that observed for PDEA microgels; presumably this is related to the greater hydrophobic character of the former particles.

Chemical Phenomena↗
PubMed2004

Enhancement of transfection efficiency through rapid and noncovalent post-PEGylation of poly(dimethylaminoethyl methacrylate)/DNA complexes.

PURPOSE: The aim of this work was to develop a new strategy to introduce poly(ethylene glycol) (PEG) into methacrylate-based polymer/ DNA complexes in order to produce hemocompatible particles able to transfect cells in the presence of serum. METHODS: Atom transfer radical polymerization was used to synthesize a well-defined poly(2-(dimethylamino)ethyl methacrylate) homopolymer (PDMAEMA) and a poly(2-(dimethylamino)ethyl methacrylate-b-poly(ethylene glycol) alpha-methyl ether, omega-methacrylate) palm-tree-like copolymer (P(DMAEMA-b-MAPEG)). The complexes obtained by self assembly of the pCMVbeta plasmid and the polymers were used to transfect Cos-7 cells. Their physical properties--particle size and zeta potential--were characterized respectively by dynamic light scattering and electrophoretic mobility measurements. Ex vivo hemocompatibility was also determined. RESULTS: The PDMAEMA/pCMVbeta complexes transfected Cos-7 cells exclusively in the absence of serum. Although the P(DMAEMA-bMAPEG) copolymer had no transfection activity per se, the addition of the latter to pre-formed PDMAEMA/DNA complexes significantly enhanced the activity and allowed transfection even in the presence of serum. The presence of palm-tree-like copolymers also improved the hemocompatibility properties of the complexes. No effect on platelet counts was observed for P(DMAEMA-b-MAPEG)/pCMVbeta complexes, whereas a decrease of platelets was clearly observed when blood cells were incubated with PDMAEMA/pCMVbeta complexes. CONCLUSIONS: Such a synergistic effect of noncovalent PEGylation of poly(amino methacrylate)/DNA complexes allows a new and versatile approach to tune up transfection efficiency.

Animals↗
PubMed2001

Exposure to airborne methacrylates and natural rubber latex allergens in dental clinics.

The exposure of dental personnel to airborne methacrylates and natural rubber latex (NRL) allergens was studied during placing of composite resin restorations in six dental clinics in Finland. Both area and personal sampling were performed, and special attention was paid to measurement of short-term emissions from the patient's mouth. Methacrylates were collected onto thermal desorption tubes filled with Tenax TA and NRL allergens onto membrane filters. The methacrylate samples were thermally desorbed and analysed by gas chromatography with mass selective detection. The NRL allergen concentrations were determined by the allergen-specific IgE-ELISA-inhibition method. The median concentration of 2-hydroxyethylmethacrylate (2-HEMA) was 0.004 mg m-3 close to the dental nurse's work-desk and 0.003 mg m-3 in the breathing zone of the nurse with a maximum concentration of 0.033 mg m-3. Above the patient's mouth the concentration of 2-HEMA was about 0.01 mg m-3 during both working stages, i.e., during application of adhesive and composite resins and during finishing and polishing of the fillings. Maximum concentrations of 3-5 times higher than median concentrations were also measured. Triethyleneglycol dimethacrylate was released into the air mainly during the removal of old composite resin restorations (0.05 mg m-3) and only to a minor extent during finishing and polishing procedures. The median concentration of the NRL allergen was 0.12 au m-3 (au = arbitrary unit) with a maximum concentration of 1.1 au m-3. The results show that, except for short-term emissions from the patient's mouth, the exposure of dental personnel to methacrylates and NRL allergens is very low. Measures to reduce exposure are discussed, as the airborne concentrations of methacrylates should be kept as low as possible in order to reduce the risk of hypersensitivity.

Air Pollution, Indoor↗