J Adv Prosthodont.  2015 Oct;7(5):386-391. 10.4047/jap.2015.7.5.386.

The effect of 4,4'-bis(N,N-diethylamino) benzophenone on the degree of conversion in liquid photopolymer for dental 3D printing

• Lee DH
• Mai HN
• Yang JC
• Kwon TY

• KMID: 2083882
• DOI: http://doi.org/10.4047/jap.2015.7.5.386

Abstract

PURPOSE
The purpose of this preliminary study was to investigate the effects of adding 4,4'-bis(N,N-diethylamino) benzophenone (DEABP) as a co-initiator to a binary photoinitiating system (camphorquinone-amine) to analyze on the degree of conversion (DC) of a light-cured resin for dental 3D printing.
MATERIALS AND METHODS
Cylindrical specimens (N=60, n=30 per group, o5 mm x 1 mm) were fabricated using bisphenol A glycerolate dimethacrylate (BisGMA) both with and without DEABP. The freshly mixed resins were exposed to light in a custom-made closed chamber with nine light-emitting diode lamps (wavelength: 405 nm; power: 840 mW/cm2) for polymerization at each incidence of light-irradiation at 10, 30, 60, 180, and 300 seconds, while five specimens at a time were evaluated at each given irradiation point. Fourier-transform infrared (FTIR) spectroscopy was used to measure the DC values of the resins. Two-way analysis of variance and the Duncan post hoc test were used to analyze statistically significant differences between the groups and given times (alpha=.05).
RESULTS
In the DEABP-containing resin, the DC values were significantly higher at all points in time (P<.001), and also the initial polymerization velocity was faster than in the DEABP-free resin.
CONCLUSION
The addition of DEABP significantly enhanced the DC values and, thus, could potentially become an efficient photoinitiator when combined with a camphorquinone-amine system and may be utilized as a more advanced photopolymerization system for dental 3D printing.

Keyword

Photopolymer; Photointiator; Degree of conversion, 4,4'-bis(N,N-diethylamino)benzophenone; 3D Printing

MeSH Terms

Glycerol
Incidence
Polymerization
Polymers
Spectrum Analysis
Glycerol
Polymers

Figure

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  Fig. 1 Chemical structures of the photoinitiators and amine synergist. CQ: camphorquinone; DMAEMA: ethyl-4-dimethylaminobenzoate; DEABP: 4,4'-bis(diethylamino)benzophenone.

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  Fig. 2 Specimen fabrication; A small amount of freshly mixed material was placed into a silicone mold, and then covered with polyester film and a glass slide to be pressed.

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  Fig. 3 (A) Custom-made closed chamber with an adjustable light-irradiation distance and (B) nine LED lamps with adjustable light-irradiation duration.

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  Fig. 4 Degree of conversion of the C=C bonds (%) as functions of the irradiation time. The lines are calculated fits of the experimental data of the equations. The solid line represents DEABP-free resin, whereas the dotted line indicates DEABP-containing resin.

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  Fig. 5 FTIR spectra of DEABP-containing and DEABP-free resins. Dotted lines (uncured); solid lines (300 s of light irradiation).

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