Archive for the ‘Research Paper’ Category

Achieving Adhesion to Metal Substrates

Monday, March 11th, 2013
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Thank you to everyone who visited us at uv.eb WEST 2013 in Redondo Beach, CA. 

Copies of our presentation, “Sticking to the Principles, Achieving Adhesion to Metal Substrates” are now available upon request.  We look forward to continuing your interesting conversations.

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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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Optimized LED cure of BisGMA:TEGDMA

Thursday, December 1st, 2011
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Micro-Raman spectroscopic analysis of the degree of conversion of composite resins containing different initiators cured by polywave or monowave LED units

Vesna Miletic a, Ario Santini b,

a Clinical Lecturer, University of Belgrade, School of Dentistry, Department of Restorative Odontology and Endodontics, Rankeova 4, Belgrade, Serbia

b Director of Biomaterials Research, The University of Edinburgh, Edinburgh Postgraduate Dental Institute, Lauriston Place, Edinburgh EH3 9HA, United Kingdom

Received 20 August 2011; revised 28 October 2011; Accepted 30 October 2011. Available online 6 November 2011.

Objectives

To determine the degree of conversion (DC) over 48 h post-curing of resin mixtures containing trimethylbenzoyl-diphenylphosphine oxide (TPO) initiator cured by a polywave or a monowave LED light-curing unit (LCU).

Methods

In resin mixtures based on equal weight percent (wt%) of BisGMA and TEGDMA the following initiators were added: 0.2wt% camphorquinone (CQ) + 0.8wt% ethyl-4-dimethylaminobenzoate (EDMAB) (Group 1); 1wt% TPO (Group 2) and 0.1wt% CQ + 0.4wt% EDMAB + 0.5wt% TPO (Group 3). Half of the samples in each group (n = 5) were cured using a polywave (bluephase® G2, Ivoclar Vivadent) or a monowave LED LCU (bluephase®, Ivoclar Vivadent). The DC was measured using micro-Raman spectroscopy within 5 min and then 1, 3, 6, 24 and 48 h post-irradiation. The data were analyzed using general linear model and two-way ANOVA for the factors ‘time’, ‘material’, ‘surface’ and ‘LCU’ at α=0.05.

Results

The initial DC values obtained upon light curing remained similar over a 48 h period. bluephase® G2 produced the highest DC in Group 2 followed by Group 3, and Group 1. bluephase® resulted in the highest DC in Group 1, followed by Group 2 and Group 3 (p < 0.05).

Conclusions

Unfilled resin materials containing both TPO- and CQ-amine initiators are effectively cured using bluephase® G2. Resin mixture with the same wt% of initiators is better cured when TPO is the only initiator, compared to CQ-amine only or combined TPO and CQ-amine system. After initial light cure, no additional conversion of uncured monomers was detected in an unfilled resin material over 48 h at 37 °C.

Materials

Page 5 of 24 Ac ce pte d M an usc rip t 4 Materials and Methods The following materials were
used in the study: bisphenol A bis(2-bydroxy-3- methacryloxypropyl)ether (BisGMA), triethylene
glycol dimethacrylate (TEGDMA)
, camphorquinone (CQ) (Esstech Inc, Essington, PA


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Urethane Dimethacrylate used in Rapid Prototyping Application

Thursday, October 13th, 2011
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Characterization of a nanoparticle-filled resin for application in scan-LED-technology

Eva Kolb, Claudia Kummerlöwe and Martin Klare

Volume 22, Number 10, 2165-2173, DOI: 10.1007/s10856-011-4411-7

Abstract

Scan-LED-technology is a new rapid prototyping technique with increasing applications in the production of custom-made medical products. The present work is dealing with the examination of a silica/urethandimethacrylate (UDMA) nanocomposite for application in scan-LED-technology. The use of specific LED in a photo-DSC unit enables the simulation of crucial parameters of nanoparticle-filled resins for their application in scan-LED-technology. The conversion of double bonds during the curing reaction and the rate of conversion were studied as a function of radiation intensity, silica nanoparticle content, and silanization of the nanoparticles with 3-methacryloyloxypropyl-trimethoxysilane (MPTMS). The conversion of double bonds is increasing with increasing radiation intensity. The increasing conversion of the nanoparticle-filled resins is discussed as a combined effect of increasing nanoparticle content, alternated initiator/double bond ratio and increasing radiation intensity. A significant dependence of the reaction rate on nanoparticle content could not be found. Only for the unfilled resin, the rate was increasing at higher radiation intensities. The influence of residual solvent on conversion and rate of reaction was also analyzed. TGA measurements combined with FTIR were used to study the silanization of the nanoparticles. The silane layer thickness on the surface of the silica nanoparticles was determined.
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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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Novel CAD-CAM Blocks Increase Load-Bearing Capacity of Dental Prostheses

Tuesday, September 6th, 2011
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Load-bearing capacity of handmade and computer-aided design–computer-aided manufacturing-fabricated three-unit fixed dental prostheses of particulate filler composite

Authors: Gööncüü Başşaran, Emine; Ayna, Emrah; Vallittu, Pekka K.; Lassila, Lippo V. J.


Overview: The load-bearing capacity of traditional CAD-CAM fabricated dental prostheses was significantly increased through the formulation of novel blocks incorporating dimethacrylate resins and silanated glass from Esstech Inc.


Objectives: To compare handmade and computer-aided design–computer-aided manufacturing (CAD-CAM)-fabricated fixed dental prostheses (FDPs) composed of a particulate filler composite.

Materials and Methods: Handmade FDPs were made of restorative composite (Z 100) and CAD-CAM-fabricated FDPs were made of commercial CAD-CAM blocks (VITA Temp) and two experimental CAD-CAM blocks of particulate filler composite. Experimental CAD composite A was prepared by mixing 31.2 wt.% of dimethacrylate resin with 68.7 wt.% of filler particles of barium oxide silicate (BaSiO2). Experimental CAD composite B was prepared by mixing 25.6 wt.% of dimethacrylate resin with 74.3 wt.% of filler particles of BaSiO2. Six groups were fabricated (n == 6 in each); FDPs were statically loaded until final fracture.

Results: Experimental CAD composites A and B revealed the highest load-bearing capacity of the FDPs, while Z 100 showed the lowest.

Conclusion: FDPs made of experimental CAD composite blocks showed higher load-bearing capacities than handmade commercial composites and commercial blocks.


Acta Odontologica Scandinavica, Volume 69, Number 3, May 2011 , pp. 144-150(7)

DOI: 10.3109/00016357.2010.545034


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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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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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Optimal Solvent Ratio for Adhesive Systems

Wednesday, June 1st, 2011
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Hybridization morphology and dentin bond stability of self-etch primers with different ethanol/water ratios

Silvia T. Fontes, Giana S. Lima, Fabrício A. Ogliari, Evandro Piva and Rafael R. Moraes

Odontology, DOI: 10.1007/s10266-011-0030-5

Abstract


This study evaluated the influence of ethanol/water ratios on the bond strength to dentin of experimental two-step, self-etch adhesive systems. Self-etch primers were prepared with constant 40 mass % of solvents. The ethanol/water ratios tested were 7:1 (P1), 3:1 (P2), and 1:1 (P3); primers with only ethanol (PE) or water (PW) as solvent were also tested. The bond strength to the dentin was investigated through a microtensile bond strength test. Resin–dentin beam-shaped specimens were obtained and tested after 24 h, 6 months, and 1 year of storage in water at 37°C. The hybridization morphology was analyzed using SEM. For bond strength at 24 h, PE = P1, P1 = P2, and P2, P3 and PW > PE. After 6 months, PE = P1 < P2, P3 and PW. After 1 year, no significant differences among the materials were detected. No significant differences among the periods were detected for PE. For P1, 24 h > 6 months = 1 year. For P2, P3 and PW, 24 h = 6 months > 1 year. For PE and P1, adhesive failures were predominant at 24 h, mixed or adhesive failures after 6 months, and premature debonding was predominant after 1 year. For P2, mixed failures were predominant at 24 h and 6 months, and premature debonding after 1 year. For P3 and PW, mixed failures were predominant at all storage periods. The SEM analysis revealed no clear differences in the hybridization patterns yielded by the water-based primers; PE showed formation of irregular resin tags.
Odontology 123 Page 6. Acknowledgments This study was partially supported by grant #04/ 1374.1 from the FAPERGS, Brazil. The authors also thank Esstech, Inc. for donating the reagents used in the present investigation


LINK:  http://www.springerlink.com/content/84hl1518hl85023w/

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