Posts Tagged ‘bis-EMA’

Esstech Resins in Antibacterial Nanocomposite

Monday, July 11th, 2011
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Development of an antimicrobial resin—A pilot study

Catherine Fan, Lianrui Chu, H. Ralph Rawls, Barry K. Norling, Hector L. Cardenas, Kyumin Whang

Dental Materials.  Volume 27, Issue 4, Pages 322-328 (April 2011)

Summary

To demonstrate that silver nanoparticles (AgNPs) could be synthesized in situ in acrylic dental resins.

Methods: Light-cure (LC; bisphenol A glycidyl methacrylate, tetraethyleneglycol dimethacrylate, bisphenol A ethoxylate dimethacrylate blend) and chemical-cure systems (CC; orthodontic denture resin) were used to synthesize AgNPs using different concentrations of Ag benzoate (AgBz).

Results: Rockwell hardness for LC resins showed that resins could be cured with up to 0.15% AgBz, while the hardness of CC resins were unaffected in the concentrations tested. UV–Vis spectroscopy and transmission electron microscopy confirmed the presence of AgNPs in both LC and CC resins. Generally, CC resins had better distribution of and much smaller AgNPs as compared to LC resins overall. In some samples, especially in LC resins, nanoclusters were visible. An in vitro release study over four-weeks showed that CC resins released the most Ag+ ions, with release detected in all samples. However, LC resins only released Ag+ ions when AgBz concentration was greater than 0.1% (w/w). AgNP-loaded CC resins made with 0.2 and 0.5% (w/w) AgBz were tested for antibacterial activity in vitro against Streptococcus mutans, and results showed 52.4% and a 97.5% bacterial inhibition, respectively. Further work is now warranted to test mechanical properties and to optimize the initiator system to produce commercially useful dental and medical resins.

Significance:  Success in this work could lead to a series of antimicrobial medical and dental biomaterials that can prevent secondary caries and infection of implants.


LINK:  http://www.demajournal.com/article/S0109-5641%2810%2900475-6/abstract


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X-726-0000, Suitable HEMA Replacement

Tuesday, July 5th, 2011
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A new approach in self-etching adhesive formulations: Replacing HEMA for surfactant dimethacrylate monomers

Cesar Henrique Zanchi,, Eliseu Aldrighi Münchow, Fabricio Aulo Ogliari, Rodrigo Varella de Carvalho, Stefano Chersoni, Carlo Prati, Flávio Fernando Demarco, Evandro Piva

Article first published online: 28 JUN 2011.  DOI: 10.1002/jbm.b.31871. © 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2011.

Abstract

This study evaluated the influence of surfactant dimethacrylates (SD) on the resin-to-dentin microtensile bond strength (μTBS) and characterized the interfacial micromorphology of the hybrid layer of the experimental HEMA-free self-etching systems. Five experimental HEMA-free two-step self-etching systems containing different SD (Bis-EMA 10, Bis-EMA 30, PEG 400, PEG 1000, and PEG 400 UDMA [Esstech Code X-726-0000]) and a HEMA-containing system (control) were compared. Each experimental adhesive system was applied and resin composite restorations were incrementally built up in bovine incisors. After 24 h, restored teeth were sectioned to obtain 24 sticks per group. Thereafter, the specimens were subjected to the μTBS test. Data (MPa) were analyzed by One-way ANOVA and Tukey’s test. Adhesive-dentin interfaces were analyzed through Scanning Electron Microscopy (SEM). The adhesive system formulated with PEG 400 UDMA produced μTBS similar to the HEMA-containing group and statistically higher than the HEMA-free groups. Similar failure percentages were observed in the PEG 400 UDMA and the control group. In the SEM analysis, all the adhesive systems presented similar partially demineralized hybrid layer (1.5–3.0 μm thickness) with well-formed resin tags. All SD presented reasonable initial μTBS, with the PEG 400 UDMA being a promising monomer to be considered as a HEMA substitute in adhesive systems compositions.


Link:  http://onlinelibrary.wiley.com/doi/10.1002/jbm.b.31871/full

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Alternative Photoinitiator Assists in Camphorquinone Cure

Tuesday, July 27th, 2010
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Degree of conversion and color stability of the light curing resin with new photoinitiator systems

Dong-Hoon Shin, H. Ralph Rawls

Dental Materials, August 2009 (Vol. 25, Issue 8, Pages 1030-1038)

Objectives: This study investigated p-octyloxy-phenyl-phenyl iodonium hexafluoroantimonate (OPPI) as a photoinitiator, in combination with camphorquinone/amine photoinitiation systems, for use with di(meth)acrylate-based composite resins. The investigation determined if the inclusion of OPPI improved degree and rate of conversion, initial color and color stability of a representative composite resin dental material.

Methods: Camphorquinone (CQ) and OPPI were combined in various proportions with the amine co-initiator 2-dimethylaminoethyl methacrylate (DMAEMA) and used at two levels in which CQ+OPPI+DMAEMA=1wt.% or 3wt.% to photoinitiate a BisGMA/BisEMA/TEGDMA (37.5:37.5:25wt.%) monomer blend. Monomer mixture (GTE) was made by mixing 37.5wt.% BISGMA (lot # 568-21-07, ESSTECH, Essington, PA), 37.5wt.% BISEMA (lot # 474-32-02, ESSTECH), and 25wt.% TEGDMA (lot # 597-23-02, ESSTECH). A total of eight groups (four groups for each level of total photoinitiator, 1% and 3%) were tested according to the following proportion of components in the photoinitiator system: Each monomer was polymerized using a quartz-halogen curing unit (Demetron 400, Demetron Research Corp., Danbury, CT) with an intensity of 400mW/cm2 for 5s, 20s, 40s, 60s, 300s and their conversion levels (DC) were determined at each exposure time using a Fourier transform infrared spectrophotometer (FTIR). To examine color stability, experimental composite resins were made by mixing 3.2% silanated barium glass (78wt.%, average filler size; 1μm) with each monomer system, except both CQ only group and 1% CO group, which were found to cure insufficiently to be able to prepare useful specimens. Disk-shaped samples (10mm in diameter and 1.5mm in thickness) were made and stored under the conditions of dry or saline solution at room temperature (25°C) or 60°C water bath. Each CIELAB scale was determined with a colorimeter (CHROMA METER CR-400) at the time of baseline (day after curing), 1 week, 2 weeks, and 4 weeks later.

Results: The high level (3%) photoinitiated groups exhibited greater DC than the low level (1%) groups. In the 3% group, the COA group showed the fastest and the highest DC, while in the 1% group the CA and COA groups showed the greatest DC. In the color stability test, both CA groups were darker and more yellow than the CO and COA groups. Color was more stable in composite resins containing OPPI than those containing only the CQ and amine components. The least color change (greatest color stability) was found using 25°C saline solution aging, and the most change (least color stability) occurred using 60°C dry air aging.

Significance: This study suggests that OPPI can be used to replace the amine in a given CQ/amine photoinitiator system to accelerate cure rate, increase conversion, reduce initial color and increase color stability.

Link: http://www.demajournal.com/article/S0109-5641%2809%2900139-0/abstract


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BisGMA:TEGDMA:UDMA Composites Present Optimal Conversion and Mechanical Properties.

Friday, May 21st, 2010
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Bis-GMA  co-polymerizations: Influence on conversion, flexural properties, fracture toughness and susceptibility to ethanol degradation of experimental composites

Carmem S. Pfeifer, Laura R. Silva, Yoshio Kawano, Roberto R. Braga

Dental Materials Volume 25, Issue 9, Pages 1136-1141 (September 2009)

Objectives

The aim of this study was to evaluate the influence of monomer content on fracture toughness (KIc) before and after ethanol solution storage, flexural properties and degree of conversion (DC) of bisphenol A glycidyl methacrylate (Bis-GMA) co-polymers.

Methods

Five formulations were tested, containing Bis-GMA (B) combined with TEGDMA (T), UDMA (U) or Bis-EMA (E), as follows (in mol%): 30B:70T; 30B:35T:35U; 30B:70U; 30B:35T:35E; 30B:70E. Bimodal filler was introduced at 80wt%. Single-edge notched beams for fracture toughness (FT, 25mm×5mm×2.5mm, a/w=0.5, n=20) and 10mm×2mm×1mm beams for flexural strength (FS) and modulus (FM) determination (10mm×2mm×1mm, n=10) were built and then stored in distilled water for 24h at 37°C. All FS/FM beams and half of the FT specimens were immediately submitted to three-point bending test. The remaining FT specimens were stored in a 75%ethanol/25%water (v/v) solution for 3 months prior to testing. DC was determined with FT-Raman spectroscopy in fragments of both FT and FS/FM specimens at 24h. Data were submitted to one-way ANOVA/Tukey test (α=5%).

Results

The 30B:70T composite presented the highest KIc value (in MPam1/2) at 24h (1.3±0.4), statistically similar to 30B:35T:35U and 30B:70U, while 30B:70E presented the lowest value (0.5±0.1). After ethanol storage, reductions in KIc ranged from 33 to 72%. The 30B:70E material presented the lowest reduction in FT and 30B:70U, the highest. DC was similar among groups (69–73%), except for 30B:70U (52±4%, p<0.001). 30B:70U and 30B:35T:35U presented the highest FS (125±21 and 122±14MPa, respectively), statistically different from 30B:70T or 30B:70E (92±20 and 94±16MPa, respectively). Composites containing UDMA or Bis-EMA associated with Bis-GMA presented similar FM, statistically lower than 30B:35T:35U.

Significance

Composites formulated with Bis-GMA:TEGDMA:UDMA presented the best compromise between conversion and mechanical properties.

This version was accepted March 23, 2009.

Link, http://www.demajournal.com/article/S0109-5641%2809%2900162-6/abstract


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Optimizing Degree of Conversion, Strength, Young’s Modulus and Hardness of Bis-EMA, Bis-GMA and TEGDMA Formulations

Tuesday, April 20th, 2010
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Preparation and Evaluation of Dental Resin Luting Agents with Increasing Content of Bisphenol-A Ethoxylated Dimethacrylate

Rafael R. Moraes, Mário A.C. Sinhoreti, Lourenço Correr-Sobrinho, Fabrício A. Ogliari, Evandro Piva, and Cesar L. Petzhold

Journal of Biomaterials Applications, Jan 2010; vol. 24: pp. 453 – 473.

Abstract: Resin luting agents in which bisphenol-A glycidyl dimethacrylate (Bis-GMA) and/or triethylene glycol dimethacrylate (TEGDMA) are replaced with increasing amounts of bisphenol-A ethoxylated dimethacrylate are prepared. Degree of conversion (DC), diametral tensile strength (DTS), Young’s modulus (YM), Knoop hardness (KHN), film thickness (FT), water sorption (Wsp ), and solubility are evaluated. Regression analyses investigate the substitution of each monomer. The most appreciable differences are detected when TEGDMA is replaced: decreased DC, DTS, and Wsp, and increased YM, KHN, and FT. For substitution of Bis-GMA, the only significant differences are reduced Wsp and increased YM. An ideal formulation of resin cement would make use of the three monomers.

…Bis-GMA, TEGDMA, and/or Bis-EMA (Esstech Inc., Essington, PA, USA) were tested…photo-curable, 0.4 wt% of camphor- quinone (Esstech) and 0.8 wt% of N,N-dimethyl-p-toluidine…silanated strontium glass fillers (Esstech), 0.7 and 2 mm in size, to a constant…

This version was published on January 1, 2010.

Link:  http://jba.sagepub.com/cgi/content/abstract/24/5/453


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Camphorquinone Decomposition Rates Vary Among UDMA and BisGMA/TEGDMA Formulations

Thursday, March 18th, 2010
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Photobleaching of camphorquinone during polymerization of dimethacrylate-based resins

Silvana Asmusen, Gustavo Arenas, Wayne D. Cook, Claudia Vallo

Dental Materials, December 2009 (Vol. 25, Issue 12, Pages 1603-1611)

Abstract: Objective: The aim of this study was to compare the photobleaching rate of CQ in different dental resins. Methods: The photodecomposition rate of CQ/amine system in bis-GMA/TEGDMA, bis-EMA and UDMA polymerizing monomers was evaluated at different light intensities. The photobleaching of the CQ was studied by monitoring the decrease in light absorption as a function of continuous irradiation time. The absorption changes were assessed by recording the transmitted light that passed through samples of monomers containing CQ/amine. Results: Complete photobleaching of CQ was observed in all the monomer tested and the rate constant for the photobleaching was proportional to the radiation intensity. Hydrogen abstraction from amines by the excited CQ state via electron transfer and direct hydrogen abstraction from monomer structures were involved in the CQ photoreduction. CQ was photobleached in the absence of coinitiator in a dimethacrylate monomer containing a carbamate functional group (UDMA). This behavior was attributed to the presence of labile hydrogen atoms in the UDMA monomer. The CQ photobleaching rate constant in UDMA containing CQ/amine was similar to that in UDMA in the absence of amine. Moreover, the efficiency of CQ to photoinitiate the polymerization of UDMA in the absence of amine demonstrated that the radicals derived from the UDMA monomer via hydrogen abstraction are highly reactive toward double bonds.

Significance: CQ photoinitiates the polymerization of the UDMA monomer in the absence of amine and the efficiency of this process is comparable to that of traditional bis-GMA and bis-EMA monomers activated with CQ/amine.

Link:  http://www.demajournal.com/article/S0109-5641(09)00285-1/abstract


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