Photopolymerization study and adhesive properties of self-etch adhesives containing bis(acyl)phosphine oxide initiator

Abstract

Objective: This paper investigates the photo-co-polymerization behavior of a blend of a diacrylamide (DEBAAP) with a phosphonylated acidic monomer using either bis(acyl)phosphine oxide or camphorquinone/amine as photo-initiator and studies the effect of variation of the structure of the phosphonylated acidic monomer on the shear bond strength to human dentin.

Methods: Photopolymerization kinetics has been assessed through the use of photo-DSC with either initiating system and with and without a phosphonic acid monomer, while the shear bond strengths (SBS) of dentin bonding agents formulated with several phosphonylated acidic monomers have been evaluated by macro SBS testing on human dentin.

Results: Photo-DSC results show that bis(acyl)phosphine oxide initiates a faster polymerization than camphorquinone/amine and that both photopolymerizations are accelerated by the phosphonic acid monomer. Similar results were obtained between adhesives based on camphorquinone/amine and a commercial adhesive (AdheSE, Ivoclar-Vivadent, Schaan, Liechtenstein). The best performances were obtained when BAPO was used as the initiator, in many cases far better than the commercial adhesive. Adhesive SEA6 based on difluoromethylphosphonic acid C demonstrated the best adhesion results of this study. Significance The bis(acyl)phosphine oxide photo-initiator causes faster photopolymerization of two-step self-etching dental adhesive, and its use could yield better bonding performance.

Keywords: Adhesion; Camphorquinone; Dental adhesives; Monomers; Phosphine oxides; Phosphonic acid; Photopolymerization; Self-etching.