Posts Tagged ‘Shrinkage’

LOW SHRINK, HIGH CONVERSION

Friday, November 11th, 2011
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EXOTHANE Elastomers

Do not sacrifice conversion and the risk of residual monomer contamination to achieve low-shrink properties.  New testing has demonstrated that EXOTHANE(TM) Elastomers have low shrinkage stress, low volumetric shrinkage, AND high conversion.

  • Exothane 8, 94% Conversion, 3% Shrinkage, high % elongation
  • Exothane 26, 96% Conversion, 4% Shrinkage, increased flexibility/toughness
  • Exothane 32, 97% Conversion, 3% Shrinkage, low color and low viscosity

This new data, in addition to superior toughness, tensilse strength and percent elongation make the EXOTHANE product line ideal form many applications including, low-shrink dental restoratives, non-curling industrial coatings, unique UV nail enhancements, tougher anaerobic adhesives and more.


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Optimal Diluent and Base Methacrylate Combinations

Thursday, September 15th, 2011
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Influence of the base and diluent methacrylate monomers on the polymerization stress and its determinants

N. R. G. Fróes-Salgado, L. C. Boaro, B. Pick, C. S. Pfeifer, C. E. Francci, M. M. Méier, R. R. Braga.  Journal of Applied Polymer Science.

Overview:

The correct pairing of methacrylate diluents and resins can optimize properties like polymerization stress, volumetric shrinkage, degree of conversion, maximum rate of polymerization, and elastic modulus in composite formulations.

Abstract:

The aim of this study was to evaluate the effect of the association between bisphenol-A diglycidyl dimethacrylate (BisGMA) or its ethoxylated version (BisEMA) with diluents derived from the ethylene glycol dimethacrylate (EGDMA), with increasing number of ethylene glycol units (1: EGDMA, 2: DEGDMA, 3: TEGDMA, or 4: TETGDMA), or trimethylol propane trimethacrylate (TMPTMA) or 1,10-decanediol dimethacrylate (D3MA) on polymerization stress, volumetric shrinkage, degree of conversion, maximum rate of polymerization (Rpmax), and elastic modulus of experimental composites. BisGMA containing formulations presented lower shrinkage and stress but higher modulus and Rpmax than those containing BisEMA. TMPTMA presented the lowest stress among all diluents, as a result of lower conversion. EGDMA, DEGDMA, TEGDMA, and TETGDMA presented similar polymerization stress which was higher than the stress presented by D3MA and TMPTMA. D3MA presented similar conversion when copolymerized with both base monomers. The other diluents presented higher conversion when associated with BisEMA. EGDMA showed similar shrinkage compared with DEGDMA and higher than the other diluents. The lower conversion achieved by TMPTMA did not jeopardize its elastic modulus, similar to the other diluents. Despite the similar conversion presented by D3MA in comparison with EGDMA and DEGDMA, its lower elastic modulus may limit its use. Rather than proposing new materials, this study provides a systematic evaluation of off the shelf monomers and their effects on stress development, as highlighted by the analysis of conversion, shrinkage and modulus, to aid the optimization of commercially available materials. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011


LINK:  http://onlinelibrary.wiley.com/doi/10.1002/app.34947/full

Article first published online: 1 SEP 2011.  DOI: 10.1002/app.34947


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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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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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Effect of Varying Filler Content in BisGMA:TEGDMA Composites

Friday, September 10th, 2010
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Contraction stress related to composite inorganic content

F. Gonçalvesa, Y. Kawanob, R.R. Bragaa

Dental Materials Volume 26, Issue 7, Pages 704-709 (July 2010).

Objectives: The role of inorganic content on physical properties of resin composites is well known. However, its influence on polymerization stress development has not been established. The aim of this investigation was to evaluate the influence of inorganic fraction on polymerization stress and its determinants, namely, volumetric shrinkage, elastic modulus and degree of conversion.

Methods: Eight experimental composites containing 1:1 BisGMA (bisphenylglycidyl dimethacrylate):TEGDMA (triethylene glycol dimethacrylate) (in mol) and barium glass at increasing concentrations from 25 to 60vol.% (5% increments) were tested. Stress was determined in a universal test machine using acrylic as bonding substrate. Nominal polymerization stress was obtained diving the maximum load by the cross-surface area. Shrinkage was measured using a water picnometer. Elastic modulus was obtained by three-point flexural test. Degree of conversion was determined by FT-Raman spectroscopy.

Results: Polymerization stress and shrinkage showed inverse relationships with filler content (R2=0.965 and R2=0.966, respectively). Elastic modulus presented a direct correlation with inorganic content (R2=0.984). Degree of conversion did not vary significantly. Polymerization stress showed a strong direct correlation with shrinkage (R2=0.982) and inverse with elastic modulus (R2=0.966).

Significance: High inorganic contents were associated with low polymerization stress values, which can be explained by the reduced volumetric shrinkage presented by heavily filled composites.

Link:  http://www.demajournal.com/article/PIIS0109564110000801/fulltext


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Esstech to detail FIT 852 at IADR 2010 Barcelona

Wednesday, June 30th, 2010
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Esstech to Present at IADR 2010

Wednesday, April 28th, 2010
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We are very excited to announce the details of our 2010 IADR presentation!

Physical Properties of New Low-Shrink Resin

Friday, July 16, 2010: 3 p.m. – 4:15 p.m.
Location: Exhibit Hall (CCIB)
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 Ctr at San Antonio, San Antonio, TX

2010 IADR Meeting Logo


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X-726-0000 Serves as HEMA Alternative and Improves Degree of Conversion

Wednesday, March 31st, 2010
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Polymerization Shrinkage and Stress Development in Amorphous Calcium Phosphate/Urethane Dimethacrylate Polymeric Composites

J.M. Antonucci, W.F. Regnault, and D. Skrtic

Journal of Composite Materials, Feb 2010; vol. 44: pp. 355 – 367. DOI: 10.1177/0021998309345180

Abstract: This study explores how substituting a new high molecular mass oligomeric poly(ethylene glycol) extended urethane dimethacrylate (UDMA) (PEG-U) for 2-hydroxyethyl methacrylate (HEMA) in photo-activated UDMA resins affects degree of vinyl conversion (DC), polymerization shrinkage (PS), stress development (PSSD) and biaxial flexure strength (BFS) of their amorphous calcium phosphate (ACP) composites. The composites were prepared from four types of resins (UDMA, PEG-U, UDMA/HEMA, and UDMA/PEG-U) and zirconia-hybridized ACP. Introducing PEG-U improved DC, while not adversely affecting PS, PSSD, and the BFS of composites. This improvement in DC is attributed to the long, more flexible structure between the vinyl groups of PEG-U and its higher molecular mass compared to poly(HEMA). The results imply that PEG-U has the potential to serve as an alternative to HEMA in dental and other biomedical applications.

…material research program supported by FDA, NIST, and ADAF. Generous contribution of UDMA, PEG- U, and HEMA monomers from Esstech, Essington, PA, USA, is gratefully acknowledged. Polymerization Shrinkage and Stress in ACP Composites 365 The authors also…

This version was published on February 1, 2010

Link: http://jcm.sagepub.com/cgi/content/abstract/44/3/355


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