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Query: EC:2.3.1.177 (BIS)
 957 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A new type of multifunctional oligomer was synthesized, and its potential as a base monomer in dental composite formulations was evaluated. The oligomer of ethoxylated bis-phenol A diacrylate (OEBPA) was prepared in good yield by a formaldehyde insertion/condensation reaction. Although double bonds along the oligomer backbone are arranged in pairs such that cyclopolymerization is possible, it is not presently known whether this process plays a significant role in the polymerization. Indirect evidence supporting efficient cyclopolymerization involves the reduced polymerization shrinkage observed for polymerized OEBPA relative to polymers of other monomers used as base resins. Photo-cured composites containing either OEBPA, BIS-GMA, or ethoxylated bis-phenol A dimethacrylate (EBPADM) as base resin and TEGDMA as diluent were compared. While the resulting diametral tensile and transverse strengths did not differ significantly, the values for the energy absorbed to failure indicated that the OEBPA- and EBPADM-based formulations yielded composites with somewhat greater toughness than that of the BIS-GMA material. This multifunctional oligomer offers mechanical strength and conversion values that are comparable with those of existing base resin monomers while providing an approximate 30% reduction in polymerization shrinkage.
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PMID:Synthesis and evaluation of novel multifunctional oligomers for dentistry. 153 3

Tensile fatigue limits and ultimate tensile strengths of some prosthodontic adhesive systems were determined. Ni-Cr-Be cylinders were: electro-etched, chemically etched, and sand-blasted prior to being bonded end-to-end with BIS-GMA and 4-META adhesives. Bonded specimens were stored in distilled de-ionized water for three days prior to being tested. Fifteen paired specimens per group were subjected to a cyclic tensile load for 1000 cycles. Tensile fatigue limits were determined by the staircase method. Five specimens per group were tested for ultimate tensile strength. In addition, those specimens which survived the 1000 cycles during fatigue testing were also tested for ultimate tensile strength. Statistical evaluations to compare tensile fatigue limits and ultimate tensile strengths for fatigued and non-fatigued specimens were then performed. The results indicated that the tensile fatigue limit and the ratio of fatigue limit to ultimate tensile strength of the sand-blasted, 4-META adhesive system were significantly lower than those of the other systems tested. The application of a cyclic load significantly decreased the ultimate tensile bond strength of the 4-META adhesive. Application of a cyclic load had no significant effect on the ultimate tensile bond strengths of the BIS-GMA systems tested.
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PMID:Tensile fatigue limits of prosthodontic adhesives. 182 69

Cell culture techniques were used to determine the source of cytotoxic agents in a commercial BIS-GMA composite. The material was polymerized according to the manufacturer's directions and leachable components were removed by room temperature extraction in ethanol, chloroform, or toluene. The leachable components in the extracts were identified using infrared spectrographic analysis. Thin layer chromatographic analysis was used to determine the number of constituents. These constituents were separated by gas chromatography and then identified by mass spectrographic analysis. Succinic dehydrogenase activity and radioactive labeling with tritiated leucine were used to evaluate cell metabolism and protein synthesis, respectively. The infrared analysis of the extracts showed that the primary component was unreacted BIS-GMA. Trace amounts of 2-hydroxy-4-methoxy-benzophenone, a light stabilizer, as well as a phenyl ester of benzoic acid which was probably degraded from BIS-GMA, were detected by the mass spectrographic method. The removal of leachable components caused a 90% decrease in toxicity compared to the nonextracted BIS-GMA samples. The extracted BIS-GMA samples showed no cellular response compared to the Teflon negative control.
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PMID:Cytotoxicity of a BIS-GMA dental composite before and after leaching in organic solvents. 182 7

Calcium metaphosphates (CMP's)--a unique class of phosphate minerals possessing polymeric structures, [Ca(PO3)2]n, and having refractive indices of approximately 1.54-1.59-- are optically compatible with resins such as BIS-GMA. In this study, several types of CMP's were prepared and evaluated for their potential as fillers for visible-light-activated (VLA) dental composites. The vitreous (V) and beta-crystalline forms of CMP were prepared by controlled thermolysis of monocalcium phosphate monohydrate, Ca(H2PO4)2.H2O. Hybrid fillers were also prepared by thermal methods. Fillers, characterized by IR spectroscopy and optical microscopy, were prepared in several size ranges (e.g., 1-100 microns). VLA composites were formulated by use of both untreated and surface modified CMP's. V-CMP and its hybrids yielded composites which expanded when stored in water but were of low strength, e.g., diametral tensile strength, (DTS) = 8 MPa. beta-CMP composites were more moisture-resistant, had higher DTS's (from 12 to 33 MPa), and showed a tendency to arrest brittle fracture. These novel fillers have potential uses in resin-based materials such as dental composites, cements, and adhesives.
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PMID:Filler systems based on calcium metaphosphates. 193 40

Polymerization shrinkage is a major limitation of dental composites. It generates internal stresses within bonded restorations and leads to marginal leakage, sensitivity and recurrent decay in the absence of adequate bonding. A method is presented for formulating composites that cure at constant volume by adding to the resin system small amounts of the hydrated mineral montmorillonite (MMT), which has been modified by replacing part of its hydration water with ammonia (NH3). The polymerization exotherm of composites containing ammonia-modified montmorillonite (NH3/MMT), cured at ambient temperatures, raises their temperature to between 60 and 80 degrees C, which causes the NH3/MMT particles to swell and counteract polymerization shrinkage. The polymerization shrinkage was measured for the BIS-GMA resin system, without filler, to which had been added NH3/MMT. The addition of 4 to 5 weight percent NH3/MMT resulted in zero polymerization shrinkage. An experimental composite was formulated using the BIS-GMA resin system, hydroxyapatite filler and 4 weight percent NH3/MMT. Cured samples developed compressive strength and hardness comparable to reported values for dental composite resins. Porosity was not detected by scanning electron microscopy. The use of NH3/MMT for formulating polymeric systems that cure at constant volume should be explored for application in direct dental composites.
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PMID:Constant-volume polymerization of composites by addition of ammonia-modified montmorillonite. 207 21

Since development of the BIS-GMA composite resin, there have been many innovations to improve the physical properties for posterior use. Subsequent development of a caries detector and chemically adhesive composite resin has further revolutionally raised the value of composite resin restoration, replacing the traditional restorative system of mechanical approach by the new system of biological approach. In this system only the infected irreversibly deteriorated insensitive tissue, stainable with the caries detector, is removed painlessly. The cavity is immediately filled with the composite resin with no further tissue reduction for retention or resistance form or extension for prevention. Both enamel and dentin walls are etched by a single etchant without lining. The chemical adhesion to the cavity margin and wall minimizes the marginal failure in size and prevalence and prevents secondary caries penetration along the wall. The chemically adhesive composite resin is thus a useful restorative material much kinder to teeth than amalgam.
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PMID:Posterior adhesive composite resin: a historic review. 209 Aug 11

The purpose of this study was to investigate in vivo enamel fluoride uptake of a slow-release boron trifluoride BIS-GMA resin material. Study subjects were orthodontic patients with at least one pair of permanent bicuspid teeth indicated for extraction. The material was applied to the buccal surface of the test tooth 1 month prior to extraction; the contralateral tooth served as the control tooth. Following extraction, the resin was removed by soaking in acetone for 36 h and polishing with a sodium bicarbonate slurry. Prior scanning electron microscopic studies have shown that this cleaning procedure effectively removes all residual resin. Enamel fluoride analyses were completed for 12 pairs of teeth from 9 subjects. The mean differences in enamel fluoride concentrations between the treated and control teeth were significantly different from zero at the 0.01 level. At each successive depth, the absolute mean amount of fluoride uptake by the test teeth was fairly constant; however, the proportional mean amount or percent increase in fluoride concentration resulting from treatment became greater in the deeper enamel layers. The data suggest that this material has the potential to provide an effective means of introducing substantial amounts of permanently bound fluoride into surface enamel, even into the deeper layers.
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PMID:In vivo study of slow-release fluoride resin and enamel uptake. 214 75

Composite restorative material has undergone gradual change in composition since its introduction in the 1960's. Early commercial resins were mixtures of BIS-GMA and TEGDMA. Today, these mixtures are still present, but urethane dimethacrylates and large oligomeric structures of BIS-GMA-urethanes exist. Because of these changes in composition, the past methods of calculating monomer conversion by means of infrared spectroscopy may need modification. This research investigates different methods used to formulate calibration curves for determination of monomer conversion by infrared spectroscopy of contemporary commercial composites containing aromatic structures. Conversion calibration procedures using various baseline methods with BIS-GMA, Bisphenol-A/TEGDMA, and a hydrogenated bonding resin were established. Both peak and area infrared absorptions were determined. One particular baseline method proved the best fit to the Beer-Lambert law. Bisphenol-A was found unsuitable as an infrared calibration model for resin composites. The BIS-GMA/TEGDMA calibration model closely simulates conversion values obtained when a hydrogenated commercial resin model was used.
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PMID:Calibration of FTIR conversion analysis of contemporary dental resin composites. 215 Aug 24

The mechanism of the hydrolytic deterioration of the silane coupling agent layer on silica filler of composite resin was examined. As a result of the desorption of the absorbed silane molecules, the contact angle between water drop and the silica plate treated with the silane coupling agent decreased when the plate was soaked in hot water and the rate of the decrease in the contact angle leveled off with an increase in the concentration of the silane coupling agent solution. With an increase in the soaking time in hot water, the strength of adhesion of poly (BIS-GMA) to the silica treated with the silane coupling agent decreased and the position of the fracture shifted from the matrix resin (adherend failure) to the silane coupling layer (adhesion failure). The time when the adhesion failure took place depended on the concentration of the silane coupling agent solution and there was the optimum concentration for water-resistant adhesion.
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PMID:[Study on surface treatment of silica filler. Hydrolytic deterioration of the silane coupling layer]. 249 Feb 2

A cone-plate viscometer was employed for studying the rheological characteristics of certain unfilled resins and etching gels. Of these, BIS-GMA monomer and its diluted mixtures exhibited Newtonian, dilatant and thixotropic behaviour depending on the shear rate. Other unfilled resins also exhibited various types of behaviour. At high shear rates reproducible hysteresis loops were obtained for etching gels which may be useful in characterization.
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PMID:The use of a cone and plate viscometer for determination of flow properties of unfilled resins and etching gels. 252 63


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