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PubMed1999

Cytochrome c-dependent methacrylate reductase from Geobacter sulfurreducens AM-1.

Geobacter sulfurreducens AM-1 can use methacrylate as a terminal electron acceptor for anaerobic respiration. In this paper, we report on the purification and properties of the periplasmic methacrylate reductase, and show that the enzyme is dependent on the presence of a periplasmic cytochrome c (apparent K(m) = 0.12 microM). The methacrylate reductase was found to be composed of only one polypeptide with an apparent molecular mass of 50 kDa and to contain, bound tightly but not covalently, 1 mol of FAD per mol. The N-terminal amino acid sequence showed sequence similarity to a periplasmic fumarate reductase from Shewanella putrefaciens. However, methacrylate reductase did not catalyze the reduction of fumarate. The periplasmic cytochrome c, which was also purified, had an apparent molecular mass of 30 kDa and contained approximately 4 mol of heme.mol(-1). Cells of G. sulfurreducens AM-1 grown on acetate and methacrylate as an energy source were found to contain all the enzymes required for the oxidation of acetate to CO(2) via the citric acid cycle.

Bacteria, Anaerobic↗
PubMed2005

Evaluation of the apical seal in root canals prepared with a new rotary system and obturated with a methacrylate based endodontic sealer: an in vitro study.

The purpose of this study was to evaluate in vitro the apical seal of root canals prepared with a new rotary system, Anatomic Endodontic Technology (AET) and filled with a methacrylate based endodontic sealer and a single gutta-percha cone and a lateral condensation technique, using the methacrylate based endodontic sealer/filler or Grossman's cement. The root canals of 45 freshly extracted human maxillary anterior teeth were prepared and then randomly assigned to three groups of 15 teeth each. After cleaning and shaping the teeth were obturated as follows: in group 1 the canals were filled with a methacrylate based sealer and a single gutta-percha cone; in group 2 the canals were filled using a lateral condensation technique with gutta-percha and the methacrylate based sealer; and in group 3, the canals were filled by means of lateral condensation of gutta-percha and Grossman's cement (control group). The specimens were stored in 100% relative humidity at 37 degrees C for 72 h, after which the coronal portion and the root surface of each tooth was covered with three layers of nail varnish and a final layer of sticky wax. After immersion in 2% methylene blue dye for 7 days, the specimens were imbedded in clear orthodontic resin and sectioned. Dye penetration was evaluated by an independent investigator using a stereo microscope. The results demonstrated that more pronounced leakage occurred in root canals obturated with the lateral condensation technique and Grossman's cement (p < 0.05). The least amount of dye leakage was observed for group 1 and 2 in which the methacrylate based sealer was used, either with a single gutta-percha cone or with lateral condensation of gutta-percha.

Dental Leakage↗
PubMed2005

Bone tissue response to a methacrylate-based endodontic sealer: a histological and histometric study.

Biocompatibility of endodontic sealers is a prime requisite for successful endodontic therapy. The purpose of this study was to evaluate the reaction of bone to a methacrylate-based endodontic sealer. Silicone tubes, filled with a methacrylate-based sealer and silicone rods used as controls, were implanted in the tibias of white male Wistar rats. Ten and 60 days after implantation the reaction of the bone was analyzed by means of histological and histometric methods. After 10 days the amount of reactionary bone in contact with the methacrylate-based sealer was significantly lower than that observed for the controls (p < 0.05). Cell counts demonstrated that the number of inflammatory cells that were in contact with the sealer were significantly higher (p < 0.05). After 60 days, no significant differences were observed in the amount of reactionary bone that was in contact with either material. The initial inflammatory reaction observed for the methacrylate-based sealer was resolved. Furthermore the cell counts demonstrated no statistically significant differences (p > 0.05) between the methacrylate based sealer and control.

Analysis of Variance↗
PubMed1977

Sensitization potentials of methyl, ethyl, and n-butly methacrylates and mutual cross-sensitivity in guinea pigs.

Guinea pigs could be strongly sensitized to methyl, ethyl, and n-butyl methacrylates in ethanol or olive oil by the topical route, or in saline by the intradermal route. For elicitation of skin reactons, topical challenge with the compounds in olive oil or intradermal challenge with saline as the solvent was neccessary. Topical challenge with the methacrylates in ethanol failed to elicit any allergic skin reactions because of their volatility. All sensitized animals responded strongly not only to the inducing methacrylate but also to the other methacrylates, showing that mutual cross-sensitivity had occurred. Since methyl methacrylate has been reported to be a potent sensitizer in humans, the guinea-pig model described here may be useful for screening products before marketing.

Acrylates↗
PubMed2001

Characterization of bone cements prepared with functionalized methacrylates and hydroxyapatite.

Bone cements prepared with methyl methacrylate and either methacrylic acid or diethyl amino ethyl methacrylate as comonomers were characterized by infrared spectroscopy, nuclear magnetic resonance, gel permeation chromatography, dynamic mechanical thermal analysis, and mechanical testing. Selected formulations containing these functionalized methacrylates were filled with hydroxyapatite and studied in terms of their properties in tension, compression and bending, and X-ray diffraction. It was found that residual monomer was not greatly affected by the presence of either acid or basic comonomers in the unfilled bone cements. In contrast, molecular weight, curing times, and glass transition temperature were composition dependent. For samples with acidic comonomer, a faster curing time, higher molecular weight, and higher glass transition temperatures were observed with respect to those with the basic comonomer. X-ray diffraction revealed that the crystalline structure was not affected by the nature of comonomer in the bone cement while scanning electron microscopy showed that hydroxyapatite remained as clusters in the bone cement. The mechanical properties of filled bone cements depended mainly on composition and type of testing. Hydroxyapatite-filled bone cements fullfilled the minimum compressive strength (70 MPa) required for bone cement use. However, the minimum tensile strength (30 MPa) was only fullfilled by cements prepared without comonomer and those containing methacrylic acid. The minimum bending strength requirement (50 MPa) was not satisfied by any of the formulations studied.

Biocompatible Materials↗
PubMed1978

Aldehyde methacrylates derived from hydroxybenzaldehydes.

Three crystalline aldehyde methacrylates with low melting points were synthesized from the readily available, isomeric hydroxybenzaldehydes and 2-bromoethyl methacrylate. These monomers can be purified by recrystallization and liquified by admixture in various proportions to obtain polymerizable liquids having workable viscosities at room temperature. These monomers may be used alone or as blends with other methacrylates since they are miscible and copolymerizable with the usual dental monomers. Also, they should be studied with other functional methacrylates designed to promote adhesion via the mineral phase to determine if this synergistic approach can improve the adhesion of dental resins to dentin. These aldehyde methacrylates, their mixtures, polymers and copolymers merit evaluation as adhesion-promoting agents for proteinaceous substrates such as bone and dentin.

Acrylates↗
PubMed1987

Glycol methacrylate as an embedding medium for bone.

A simple and reliable procedure for embedding undecalcified trabecular bone tissue in noncommercial glycol methacrylate (GMA) has been developed. The embedding mixture includes a monomer, methacrylic acid hydroxyethyl ester; a copolymer, methacrylic acid butyl ester; a cross-linker, ethylene glycol dimethacrylate; a catalyst, Luperco; a chemical initiator (N,N-dimethylaniline) and, to avoid excessive elevation of temperature during polymerization, a heat moderator, alpha-terpinene. The appropriate proportions of these components have been selected to give specimens which can be easily sectioned with classical microtomes and which do not swell but spread evenly on a water surface. Since polymerization occurs at -4 C, the method allows demonstration of such enzymatic activities as acid and alkaline phosphatase and carbonic anhydrase. It provides excellent preservation of bone tissue and in studies of bone metabolism allows histomorphometry as well as visualization of fluorescent labeling and radioactive markers. The cost is significantly less than available commercial kits. In our hands glycol methacrylate is at present more useful than methyl methacrylate and is used in our laboratory for routine embedding of bone tissue.

Acrylates↗
PubMed1981

[Irritation and allergy to acrylates and methacrylates. - Part I: Common monoacrylates and monomethacrylates (author's transl)].

Acrylates and methacrylates are industrial chemicals with insufficiently known irritating and allergenic effects. In this paper, the simple monoacrylates and monomethacrylates are considered. Methyl acrylate is an irritant, giving a reaction in 10 out of 30 patients, when tested at 20 p. 100 in olive oil. It is also an allergen (2 out of 22 cases). Because of its irritating properties, the concentration of 2 p. 100 is proposed for allergeric investigations. Methyl methacrylate, at 20 p. 100 in olive oil, is not an irritant for humans, although we have observed a sensitization rate of about 15 p. 100 with an undiluted product. In animal studies (technic of Kligman and Magnusson), 10 p. 100 of the subjects reacted to a working concentration of 1 p. 100 in petrolatum (allergenicity degree II). A risk of sensitization due to test repetition exists, about 9 p. 100 and 15 p. 100 for methyl acrylate (20 p. 100) and undiluted methyl methacrylate, respectively. For the latter, sensitization appears around the 16 th-18th day and may be preceeded by an irritation (1 out of 3 cases). Allyl acrylate and allyl methacrylate are irritants which should be studied at a concentration of about 0,1 p. 100. A 5 p. 100 concentration in olive oil seems appropriate for studying allergies to the following monoacrylates and monomethacrylates: acrylamide and acrylonitrile, n-butyl, cyclohexyl, ethyl, ethyl-2-hexyl, ethoxy-2-ethyl, phenyl acrylates, cyclohexyl dodecyl, ethyl-2-hexyl, ethoxy-2-ethyl, methyl methacrylates.

Acrylates↗
PubMed1979

Influence of methyl methacrylate on quantitative gel diffusion assay of immunoglobulins.

Infection is not a common problem following implant surgery using the bone cement, polymethyl methacrylate. When infection occurs, its often disastrous results makes for major complications. Many methods have been used in an attempt to reduce bacterial contamination at the time of implant surgery, but little attention has been given to the problem of possible effects of implant materials on the immune mechanisms of the host. In the experiments reported here, the in vitro effect of methyl methacrylate monomer on human immunoglobulins was determined using a quantitative gel diffusion technique. When methyl methacrylate monomer was added to serum samples containing immunoglobulin, it caused no statistically significant change in the immunoglobulin concentration of immunoglobulin-G, immunoglobulin-A, or immunoglobulin-M. It is possible that methyl methacrylate could affect other types of antigen antibody reactions which may be important in resisting infection, but the evidence reported here indicates that in low concentrations, methyl methacrylate monomer does not affect the normal reactivity of immunoglobulins of the G, M, or A class.

Agar↗
PubMed1980

Methyl methacrylate concentrations in tissues adjacent to bone cement.

The amount of methyl methacrylate monomer present in bone tissue immediately adjacent to implanted bone cement that has polymerized in vivo has been determined. Poly(methyl methacrylate) was implanted into the distal femoral condyle of the dog and allowed to polymerize. At various times following polymerization, samples were removed and sections adjacent to the cement were cut and subjected to homogenization followed by liquid gas chromatographic determination of the amount of methyl methacrylate monomer present. The highest concentration of methyl methacrylate monomer present in bone tissue was 0.140% in the 1000 micrometers of bone tissue adjacent to bone cement immediately after polymerization of the cement. The concentration was very similar (0.137%) 1 hr after cement polymerization, but dropped off rapidly following that with no free methyl methacrylate monomer present in bone tissue adjacent to cement after 4 hr following cement polymerization.

Animals↗
PubMed1994

Wetting the repair surface with methyl methacrylate affects the transverse strength of repaired heat-polymerized resin.

This study investigated the transverse strength of repaired test specimens of heat-cured acrylic resin. The repair surfaces of the specimens were wetted with methyl methacrylate for various amounts of time before the autopolymerizing acrylic resin was applied to the joint space. A three-point loading test was used to determine the transverse strength of the test specimens, and the morphologic changes in the methyl methacrylate-wetted repair surface was analyzed by scanning electron microscopy. Visual inspection was used to determine whether the failures were adhesive or cohesive. The results revealed that repaired test specimens were weaker than those unrepaired (p < 0.001). The strength of the test specimens increased as the duration of methyl methacrylate wetting of the repair surfaces increased (p < 0.001). Furthermore, the number of adhesive failures was small if the repair surfaces were adequately wetted with methyl methacrylate. Scanning electron micrographs revealed that after 60- and 180-second wetting periods, the poly(methyl methacrylate) was noted to be dissolved with a smooth surface texture. This study suggests that proper wetting of the repair surface makes an important contribution to the strength of repaired acrylic resin.

Acrylic Resins↗
PubMed1994

Analysis of fume emission from ultrasonic removal of methyl methacrylate cement in revision hip surgery.

Fumes emitted from the ultrasonic instrument while removing polymethyl methacrylate cement were analyzed in three separate phases: phase 1, cement removal from bovine femur in the laboratory; phase 2, methyl methacrylate fumes collected at primary cemented total knee arthroplasty; and phase 3, fumes collected at revision hip surgery. These fumes were collected via personal sampling pumps worn by operating room personnel to determine personal levels of exposure. In phase 1 peak levels of methyl methacrylate and butyl methacrylate were obtained. Phase 2 revealed the highest levels of methyl methacrylate to be only 1 part per million or less (well below the National Institute for Occupational Safety and Health recommended exposure limit of 100 parts per million), and in phase 3 there were no detectable levels of toxic substances. Therefore, we feel that the fumes emitted from the use of ultrasound in revision total hip arthroplasty are safe.

Air Pollutants, Occupational↗
PubMedDate not supplied

Effect of reaction parameters on synthesis of citronellyl methacrylate by lipase-catalyzed transesterification.

The methacrylate ester of citronellol was synthesized using various lipases as catalyst. The effect of different reaction parameters such as amount of lipase, solvent, temperature, and acylating agent on the conversion of citronellol to citronellyl methacrylate was studied. Methyl methacrylate, vinyl methacrylate, and 2,3-butanedione mono-oxime methacrylate were used as acylating agents. Porcine pancreatic lipase (PPL), Candida rugosa lipase (CRL), and Pseudomonas cepacia lipase (Amano-PS) were used as biocatalysts. Diisopropyl ether (DIPE) was found to be the most suitable solvent. The stereoselectivity of CRL in transesterification of (+/-)-citronellol was tested for the optimized reaction parameters.

Acyclic Monoterpenes↗
PubMed2004

(Butadiene)metallocene/B(C6F5)3 pathway to catalyst systems for stereoselective methyl methacrylate polymerization: evidence for an anion dependent metallocene catalyzed polymerization process.

The ansa-zirconocene dichlorides [Me(2)Si(C(5)H(4))(3-R-C(5)H(3))]ZrCl(2) 7a-e (R = H, CH(3), cyclohexyl, -CHMe(2), -CMe(3)) were reacted with butadiene-magnesium to yield the respective (eta(4)-butadiene)metallocenes 17a-e. The chiral examples give a mixture of two s-cis and two s-trans diastereomers. The strong Lewis acid B(C(6)F(5))(3) adds selectively to a terminal butadiene carbon atom to yield the (butadiene)metallocene/B(C(6)F(5))(3) betaine complexes 18a-e. Initially, the formation of the Z-18 isomers is preferred. These consecutively rearrange to the thermodynamically favored isomers E-18. The dipolar systems 18 are active single component metallocene catalysts for the stereospecific polymerization of methyl methacrylate. With increasing steric bulk of the attached single alkyl substituent an increasingly isotactic poly(methyl methacrylate) is obtained. A similar trend is observed in the methyl methacrylate polymerization at the [Me(2)Si(C(5)H(4))(3-R-C(5)H(3))]ZrCH(3)(+) catalysts (9a-e) that were conventionally prepared by methyl abstraction from the corresponding ansa-zirconocene dimethyl complexes by treatment with B(C(6)F(5))(3). A comparison of the poly(methyl methacrylates) obtained at these two series of catalysts has revealed substantial differences in stereoselectivity that probably originate from an influence of the respective counteranions. An initial reactive intermediate of methyl methacrylate addition to the dipolar single component metallocene catalyst E-18a was experimentally observed and characterized by NMR spectroscopy at 253 K. The subsequently formed series of [PMMA-C(4)H(6)(-)B(C(6)F(5))(3)](-) anion oligomers (at the catalyst 18c) was monitored (after quenching) and characterized by electrospray mass spectrometry.

Journal Article↗
PubMed1999

Water sorption behaviour of polymeric systems based on tetrahydrofurfuryl methacrylate.

Earlier research has described the water absorption behaviour, drug release and biological properties of a room temperature polymerizing system based on poly(ethyl methacrylate) (PEM) powder and tetrahydrofurfuryl methacrylate (THFM) monomer. This work has been extended, with respect to water sorption behaviour, by replacing the monomer to various extents with hydroxyethyl methacrylate (HEMA), and poly(ethyl methacrylate) by ethyl methacrylate (EM)-THFM copolymers. Replacing the THFM with HEMA, and gelling with PEM, increased the diffusion coefficient progressively. The replacement of PEM by EM-THFM copolymers, when gelled with THFM monomer, substantially reduced equilibrium water uptake, and increased diffusion coefficients. However, with HEMA monomer, equilibrium uptake was unaffected, but the diffusion coefficient decreased with increasing THFM content of the copolymer. This is due to a complex interaction of THFM cross-linking the copolymer, and the effect of EM on the water uptake. Heat polymerizing the PEM-THFM system reduced equilibrium uptake and the diffusion coefficient, compared with the room temperature polymerizing system; this could reflect molecular weight differences.

Journal Article↗
PubMedDate not supplied

Evaluation of exposure to methyl methacrylate among dental laboratory technicians.

Following the diagnosis of two cases of occupational asthma among dental technicians, an industrial hygiene survey was conducted in two dental laboratories to determine time-weighted average and peak concentrations of methyl methacrylate vapor and time-weighted average concentration of acrylic dust. The time-weighted average concentrations of methyl methacrylate vapor were 0.7 ppm and 1.6 ppm and average peak concentrations were 9.3 ppm and 9.7 ppm for the first and second laboratory, respectively. The use of a local exhaust ventilation system was significant in reducing the peak concentration of methyl methacrylate vapor in the breathing zone of dental technicians. However, the local exhaust ventilation was not efficient in reducing the concentration of airborne acrylic dusts. Occupational exposure of dental technicians to dental materials, in particular to methyl methacrylate, requires further investigation. Local exhaust ventilation systems can reduce the concentration of methyl methacrylate in the dental laboratories to a significant extent if installed and used properly.

Air Pollutants, Occupational↗
PubMed1997

Use of methyl methacrylate resin for embedding bone marrow trephine biopsy specimens.

AIMS: To evaluate the use of methyl methacrylate resin as an embedding medium for undecalcified bone marrow trephine biopsy specimens. METHODS: About 2500 undecalcified bone marrow trephine biopsy specimens were processed, and embedded in methyl methacrylate resin. Semithin sections (2-3 microns) were stained by routine tinctorial and immunocytochemical staining methods with a wide range of antibodies using a standard streptavidin biotin horseradish peroxidase technique. Different antigen retrieval pretreatments were evaluated. RESULTS: Bone marrow trephine biopsy specimens are embedded routinely in methyl methacrylate at the Haematological Malignancy Diagnostic Service at The Leeds General Infirmary. Over 50 different primary antibodies are in current use; for the majority of these, microwave antigen retrieval or trypsin digestion, or both, is either essential or greatly enhances the results. CONCLUSIONS: Embedding bone marrow trephine biopsy specimens in methyl methacrylate resin retains morphology and permits reliable, high quality immunocytochemistry. This is particularly desirable for the demonstration of neoplastic cells in regenerative marrow after chemotherapy, and in the detection of residual disease after treatment. The use of methyl methacrylate for routine use on bone marrow trephine biopsy specimens is advocated.

Biopsy↗
PubMed1996

Percutaneous vertebroplasty for osteolytic metastases and myeloma: effects of the percentage of lesion filling and the leakage of methyl methacrylate at clinical follow-up.

PURPOSE: To determine whether the percentage of vertebral lesion filling and the leakage of methyl methacrylate have any clinical significance at follow-up. MATERIALS AND METHODS: Forty percutaneous vertebroplasties were performed for metastases (30 cases) and myeloma (10 cases) in 37 patients. A computed tomographic scan was obtained 1-8 hours after methyl methacrylate injection and was used to assess the percentage of lesion filling by methyl methacrylate and the leakage of methyl methacrylate into the epidural tissues, neural foramina, intervertebral disks, venous plexus, and paravertebral tissue. The results were correlated with those obtained at clinical follow-up. RESULTS: Partial or complete pain relief was sustained in 36 of 37 patients. Pain relief was not proportional to the percentage of lesion filling. Clinical improvement was maintained in most patients. The 15 epidural leaks, eight intradiskal leaks, and two venous leaks of methyl methacrylate had no clinical importance. Two of eight foraminal leaks produced nerve root compression that required decompressive surgery. One of 21 paravertebral leaks produced transitory femoral neuropathy. CONCLUSION: Pain relief can occur despite insufficient lesion filling. In most patients, intradiskal and paravertebral leaks of cement had no clinical importance.

Bone Cements↗