Posts Tagged ‘CQ’

Dental Photoinitiators

Friday, March 8th, 2013
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Simply described, photoinitiators are chemicals that generate radicals upon exposure to light.  A more complete description would include all the complexities inherent with the chemical nature of photoinitiators including type, concentration and absorptivity.  All of these factors must be taken into consideration when optimizing a light-curable formulation.

With PL Industries, the new division of Esstech Inc., we can now provide the monomers, adhesion promoters, oligomers, photoinitiators and technical expertise to guide you in your material selection.  The following is an example of our photoinitiator products.

 

PL-CQ
Camphorquinone
Absorption Range:  400-550 nm, 470 nm peak

Description:  Type II, fine yellow powder, very common and effective for dental restoratives, heat aids in dissolution

PL-TPO
2,4,6-Trimethylbenzoyl-diphenylphosphine oxide
Absorption Range: 230-430 nm, 385 nm peak

Description:  Type I, off-white, crystalline powder, dissolves in most monomers, exhibits photo-bleaching properties

PL-PPD
1-Phenyl 1,2-propanedione (PPD)
Absorption Range:  300-480 nm, 393 nm peak

Description:  Type II, yellow liquid, believed to have a lower rate of polymerization that is not detrimental to overall conversion

PL-EDB
Ethyl-4-dimethylamino benzoate
(EDAB, EDMAB)

Description:  a tertiary amine synergist typically used in combination with type II photoinitiators such as PL-CQ

X-866-0000
Dihydroxyethyl-para-toluidine
(DHEPT)

Description:  solid, off-white amine co-initiator that is low in color, requires melting or crushing to simplify incorporation

X-867-0000
2-dimethylaminoethyl methacrylate
(DMAEMA, MADAME)

Description:  a clear, colorless liquid used as an amine synergist for type II photoinitiators, commonly used in 1:2 ratio with CQ

Contact Us to request samples and more information at techsupport@esstechinc.com .

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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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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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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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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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