Posts Tagged ‘composite’

TPO Evaluated in Dental Composites

Monday, January 9th, 2012
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Curing efficiency of dental resin composites formulated with camphorquinone or trimethylbenzoyl-diphenyl-phosphine oxide

Luis Felipe J. Schneider, Larissa Maria Cavalcante, Scott A. Prah, Carmem S. Pfeifer, Jack L. Ferracane.  “Curing efficiency of dental resin composites formulated with camphorquinone or trimethylbenzoyl-diphenyl-phosphine oxide” Dental Materials.  December 2011:  Online

Summary:

This research presents trimethylbenzoyl-diphenyl-phosphine oxide (TPO) as an alternative to camphorquinone (CQ) photoinitiator systems for dental resins.  An immediate advantage is the low color of TPO in comparison to the strong yellow color of CQ. Testing using a spectrophotometer and differential scanning calorimetry (DSC) revealed that TPO had higher reactivity than CQ.  CQ exhibited higher absorbed power density, (PDabs) and better depth of cure.

Materials

Testing of each photoinitiator was performed using 50:50 formulations of 2,2-bis[4-2(2-hydroxy-3-
methacroyloxypropoxy)phenyl]propane (Bis-GMA, Esstech) and triethyleneglycol dimethacrylate (TEGDMA, Esstech).


LINK:  http://dx.doi.org/10.1016/j.dental.2011.11.014

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Introducing EXOTHANE Elastomers

Wednesday, September 28th, 2011
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EXOTHANE Elastomers

Optimize Photocurable Mechanical Properties

EXOTHANE™ Elastomers represent the most recent advances in Esstech’s urethane chemistry. These versatile materials offer performance enhancements across a broad range of demanding formulations.

  • Exothane 8, low color urethane, creates a “soft” yet tough polymer with high elongation
  • Exothane 26, high flexibility when cured, has the ability to re-adhere at lower tensile strength
  • Exothane 24, high crosslink capacity, low in color and viscosity and very high Shore D hardness
  • Exothane 32, very low in color and viscosity, provides improved flexibility

Like many of Esstech’s other products, potential applications involving EXOTHANE™ Elastomers can vary across many industries from medical devices and nail gel enhancements to radiation-curable coatings.

Contact us directly to discuss your unique requirements and request our EXOTHANE™ Elastomers Product Literature.

Phone: 1-800-245-3800 or 610-521-3800
EMail: techsupport@esstechinc.com.

Esstech products are available to our European customers via, Esschem Europe

(www.esschem-europe.com).



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FIT 852 Shrinkage / Conversion Data

Thursday, July 28th, 2011
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Click on the following link for a pdf download of our poster.

Physical Properties of a New Low Shrink Resin

A. JOHNSTON1, F. RUEGGEBERG2, H.R. RAWLS3, H. SLAFF1, T. BARCLIFT1, and J. DUFF1, 1Esstech Inc, Essington, PA, 2Medical College of Georgia, Augusta, GA, 3University of Texas Health Science Center at San Antonio, San Antonio, TX

Introduction:

The improvement of aesthetic restorative dental composites can be pursued on many fronts. A composite is made from multiple components but, generally, it is a blend of finely ground glasses and reactive monomers.  The monomers cure to provide a continuous polymer matrix for retaining the glass.  Together they present a hard surface with the capability to survive in the oral environment.  Failure of these composites is a complex phenomenon.   While clinical failure can occur when the adhesive force between the composite and the vital dental tissue is compromised, failure also occurs when stresses overcome the cohesive strength of the continuous phase of the mixture.   Catastrophic material failure can occur as wear against complementary dentition that slowly erodes the surface.   Those cracks through the polymer phase lead to composite failure.  To improve the composite properties, a new monomer has been introduced, FIT 852 Resin™, that can provide greater toughness in the polymer, greater extent of cure in the polymer, lower shrinkage stress and no change in composite material manufacture.


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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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Reduced Shrinkage Stress with Optimized BisGMA/TEGDMA Ratios

Thursday, May 5th, 2011
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BisGMA/TEGDMA ratio and filler content effects on shrinkage stress

Flávia Gonçalve, Caio L.N. Azevedo, Jack L. Ferracane,Roberto R. Braga
Dental Materials, Volume 27, Issue 6, Pages 520-526 (June 2011)

Abstract

Objective

To investigate the contributions of BisGMA:TEGDMA and filler content on polymerization stress, along with the influence of variables associated with stress development, namely, degree of conversion, reaction rate, shrinkage, elastic modulus and loss tangent for a series of experimental dental composites.

Methods

Twenty formulations with BisGMA:TEGDMA ratios of 3:7, 4:6, 5:5, 6:4 and 7:3 and barium glass filler levels of 40, 50, 60 or 70wt% were studied. Polymerization stress was determined in a tensilometer, inserting the composite between acrylic rods fixed to clamps of a universal test machine and dividing the maximum load recorded by the rods cross-sectional area. Conversion and reaction rate were determined by infra-red spectroscopy. Shrinkage was measured by mercury dilatometer. Modulus was obtained by three-point bending. Loss tangent was determined by dynamic nanoindentation. Regression analyses were performed to estimate the effect of organic and inorganic contents on each studied variable, while a stepwise forward regression identified significant variables for polymerization stress.

Results

All variables showed dependence on inorganic concentration and monomeric content. The resin matrix showed a stronger influence on polymerization stress, conversion and reaction rate, whereas filler fraction showed a stronger influence on shrinkage, modulus and loss tangent. Shrinkage and conversion were significantly related to polymerization stress.

Significance

Both the inorganic filler concentration and monomeric content affect polymerization stress, but the stronger influence of the resin matrix suggests that it may be possible to reduce stress by modifying resin composition without sacrificing filler content. The main challenge is to develop formulations with low shrinkage without sacrificing degree of conversion.

LINK:  http://www.demajournal.com/article/S0109-5641%2811%2900020-0/abstract


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BisGMA – UDMA Composite with Nanosilica Fibers

Tuesday, March 29th, 2011
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Synthesis of Nanosilica Fillers for Experimental Dental Nanocomposites and Their Characterisations
Tuan Noraihan Azila Tuan Rahim1, Dasmawati Mohamad1*, Abdul Rashid Ismail1 and Hazizan Md Akil2

1School of Dental Sciences, Universiti Sains Malaysia,
2School of Material and Mineral Resources Engineering, Universiti Sains Malaysia

MATERIALS:

Tetraethyorthosilicate (TEOS), absolute ethanol, ammonia,  γ-methacryloxypropyl-trimethoxysilane (γ-MPS), acetic acid (CH3COOH), bisphenol A glycidyl methacrylate (BisGMA, Esstech), diurethane dimethacrylate (UDMA), triethylene glycol dimethacrylate (TEGDMA), camphorquinone (CQ), (2-dimethylaminoethyl) methacrylate (DMAEMA) and distilled water were used in this work. The chemicals were employed without any further purification.

ABSTRACT:

The aim of this study was to synthesise nanosilica fillers for use in the fabrication of experimental dental nanocomposites and to evaluate their properties,  including surface and mechanical properties. Monodispersed, spherical silica nanoparticles were synthesised via a sol-gel process, and a size range of 10–20 nm was obtained. Surface treatment of the nanosilica was carried out with the silane coupling agent γ-methacryloxypropyltrimethoxysilane (MPS) to reduce agglomeration of nanosilica. Experimental dental nanocomposites with two different filler contents, 30 and 35 wt%, were fabricated and polymerised with a light curing unit for 40 s. The surface morphology, surface roughness, flexural strength and elastic modulus were evaluated and compared. A nanocomposite with 35% filler content showed higher filler compaction, lower surface roughness and higher elastic modulus than a nanocomposite filled with 30% filler. However, the nanocomposite filled with 30% filler content showed higher flexural strength. Based on the results obtained, the synthesised nanosilica is a promising material for the fabrication of dental nanocomposites for tooth-filling applications.



LINK:  http://web.usm.my/jps/22-1-11/22.1.6.pdf


Journal of Physical Science, Vol. 22(1), 93–105, 2011
© Penerbit Universiti Sains Malaysia, 2011

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BISGMA & TEGDMA Form Polymer Matrix of Montmorillonite Nanocomposites

Monday, March 7th, 2011
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Preparation and characterization of light-cured methacrylate/montmorillonite nanocomposites

Veronica Mucci, Javier Perez, Claudia I Vallo


ABSTRACT

Polymer/clay nanocomposites were prepared from dimethacrylate monomers, commonly used in dental restorative resins, and an organically modified silicate (montmorillonite). The photopolymerization process was hardly affected by the presence of the silicate filler, and thus 2 mm thick samples containing 3 wt% clay were extensively cured. Transmission electron microscopy revealed that the montmorillonite platelets were either intercalated or exfoliated. Nevertheless, for all formulations, intermediate-sized aggregates of about 1 µm were present and their fraction increased as the amount of filler increased. The presence of the clay was found to have no major effect on the flexural modulus and compressive yield strength of the nanocomposites. Moreover, the water uptake of nanocomposites containing 3 wt% clay was about 10–15% higher than that of unfilled monomers. Modification of the clay surface with alternative organic cations is certainly necessary in order to achieve an optimal dispersion of the clay in the polymer matrix.

The methacrylate monomers used for the preparation of the nanocomposites were 2,2-bis[4-(2-methacryloxyethoxy)phenyl]pro-pane  (BisEMA; from Esstech, Essington, PA), triethylene glycoldimethacrylate and 1,6-bis(meth-acrylyloxy-


Article first published online: 14 OCT 2010.  DOI: 10.1002/pi.2935.  Copyright © 2010 Society of Chemical Industry

LINK:  http://onlinelibrary.wiley.com/doi/10.1002/pi.2935/full


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UDMA – TEGDMA Viable Resin System for Chlorhexidine Release

Thursday, June 17th, 2010
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Controlled Release of Chlorhexidine from UDMA-TEGDMA Resin

K.J. Anusavice, N.-Z. Zhang and C. Shen

J DENT RES 2006; 85; 950

ABSTRACT
Chlorhexidine salts are available in various formulations for dental applications. This study tested the hypothesis that the release of chlorhexidine from a urethane dimethacrylate and triethylene glycol dimethacrylate resin system can be effectively controlled by the chlorhexidine diacetate content and pH. The filler concentrations were 9.1, 23.1, or 33.3 wt%, and the filled resins were exposed to pH 4 and pH 6 acetate buffers. The results showed that Fickian diffusion was the dominant release mechanism. The rates of release were significantly higher in pH 4 buffer, which was attributed to the increase of chlorhexidine diacetate solubility at lower pH. The higher level of filler loading reduced the degree of polymerization, leading to a greater loss of organic components and higher chlorhexidine release rates.

Link:  http://jdr.sagepub.com/cgi/content/abstract/85/10/950


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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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Dental Materials Blog

Tuesday, May 4th, 2010
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It’s our pleasure to present the Dental Materials Blog.

This blog presents topics of interest to dentists, material scientists and PhD students. Feel free to browse around and leave comments.  Recent Posts include:

Dental Materials Blog is coordinated by the Santini Miletic Research Group.  Providing research focused on Recent research has focused on dental resin based composites and adhesives using Raman Spectroscopy, High performance liquid chromatography, Scanning and Transmission Electron Microscopy and Atomic Force Microscopy.  You can contact the Santini Miletic Research Group at: info@santinimiletic.com

Santini Miletic Research

Santini Miletic Research


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