title: The effect of 4,4'-bis(N,N-diethylamino) benzophenone on the degree of conversion in liquid photopolymer for dental 3D printing.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  Cylindrical specimens (N=60, n=30 per group, ø5 mm × 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/cm(2)) 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 (α=.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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Prosthodontics, School of Dentistry, Kyungpook National University, Daegu, Republic of Korea.
authors.forename: Du-Hyeong
authors.initials: DH
authors.lastname: Lee
authors.affiliation: Department of Prosthodontics, School of Dentistry, Kyungpook National University, Daegu, Republic of Korea.
authors.forename: Hang Nga
authors.initials: HN
authors.lastname: Mai
authors.affiliation: Department of Polymer Science & Engineering, School of Applied Chemical Engineering, Kyungpook National University, Daegu, Republic of Korea.
authors.forename: Jin-Chul
authors.initials: JC
authors.lastname: Yang
authors.affiliation: Department of Dental Biomaterials, School of Dentistry, Kyungpook National University, Daegu, Republic of Korea.
authors.forename: Tae-Yub
authors.initials: TY
authors.lastname: Kwon
keywords: 3D Printing; Degree of conversion, 4,4'-bis(N,N-diethylamino)benzophenone; Photointiator; Photopolymer