Dental Materials
Volume 22, Issue 6 , Pages 576-584, June 2006

The initiating radical yields and the efficiency of polymerization for various dental photoinitiators excited by different light curing units

  • Miguel G. Neumann

      Affiliations

    • Instituto de Química de São Carlos, Universidade de São Paulo, Caixa Postal 780, 13560-970 São Carlos SP, Brazil
    • Corresponding Author InformationCorresponding author. Tel.: +55 16 3373 9940; fax: +55 16 3373 9952.
    • ,
  • Carla C. Schmitt

      Affiliations

    • Instituto de Química de São Carlos, Universidade de São Paulo, Caixa Postal 780, 13560-970 São Carlos SP, Brazil
    • ,
  • Giovana C. Ferreira

      Affiliations

    • Instituto de Química de São Carlos, Universidade de São Paulo, Caixa Postal 780, 13560-970 São Carlos SP, Brazil
    • ,
  • Ivo C. Corrêa

      Affiliations

    • Faculdade de Odontologia, Universidade Federal do Rio de Janeiro, Av Brigadeiro Trompowsky s/n, 21949-900 Rio de Janeiro RJ, Brazil

Received 19 April 2005; accepted 16 June 2005.

Summary 

Objectives

To evaluate the efficiency of the photopolymerization of dental resins it is necessary to know to what extent the light emitted by the light curing units is absorbed by the photoinitiators. On the other hand, the efficiency of the absorbed photons to produce species that launch the polymerization process is also of paramount importance. Therefore, the previously determined PAE (photon absorption efficiency) is used in conjunction with the polymerization quantum yields for the photoinitiators, in order to be able to compare the total process on an equivalent basis. This parameter can be used to identify the best performance for the photochemical process with specific photoinitiators.

Methods

The efficiency of LED (Ultrablue IS) and QTH (Optilux 401) lamps were tested comparing their performances with the photoinitiators camphorquinone (CQ); phenylpropanedione (PPD); monoacylphosphine oxide (Lucirin TPO); and bisacylphosphine oxide (Irgacure 819). The extent of photopolymerization per absorbed photon was determined from the polymerization quantum yields obtained by using the photoinitiators to polymerize methyl methacrylate, and afterwards combined with the previously determined PAEs.

Results

Although CQ presents a rather low polymerization quantum yield, its photopolymerization efficiency is practically the highest when irradiated with the Ultrablue LED. On the other hand, Lucirin is much more efficient than the other photoinitiators when irradiated with a QTH lamp, due to its high quantum yield and the overlap between its absorption spectrum and the output of the visible lamp light.

Significance

Difference in photopolymerization efficiencies arise when combinations of photoinitiators are used, and when LED sources are used in preference to QTH. Mechanistic understanding is essential to optimal initiator formulation.

Keywords: Dental photoinitiators, Light emitting diode (LED), Quartz–tungsten–halogen (QTH), Photopolymerization efficiency

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PII: S0109-5641(05)00232-0

doi:10.1016/j.dental.2005.06.006

Dental Materials
Volume 22, Issue 6 , Pages 576-584, June 2006

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