Low-Migration Compounds with Amine Functionality as Co-Initiators of Radical Polymerization.

The utilization of two-component systems comprising camphorquinone (CQ) and aromatic amines has become prevalent in the photopolymerization of dental adhesives and composites. However, there are still concerns about the safety of this CQ/amine system, mainly because of the toxicity associated with the leaching of aromatic amines from dental materials. In light of these concerns, this study aims to develop novel co-initiator combinations featuring CQ and amines which cannot be leached out of dental materials, enabling free radical polymerization of representative dental methacrylate resins under blue light irradiation. Our approach involved the initial design and analysis of hydrogen donors with low C-H bond dissociation energy through molecular modeling. Subsequently, we incorporated copolymerizable methacrylate functional groups via chemical modification, allowing it to act as both coinitiator and copolymerization monomer to achieve low migration and leachability properties. This work presents, for the first time, the synthesis of the innovative co-initiator and compares its performance with the benchmark CQ/ethyl-4-dimethylaminobenzoate (EDB)-based photoinitiation system (PIS). The results demonstrate the effectiveness of the newly proposed PIS, with the comparable or superior polymerization properties were obtained when acrylate resins were subjected to photopolymerization using blue dental LEDs in ambient air. Furthermore, the system exhibited remarkable bleaching capabilities. Moreover, the elastic modulus of the resulting polymer was substantially enhanced. Finally, we conducted an in-depth investigation into the reaction mechanism associated with this PIS through molecular orbital calculations and electron spin resonance studies. This article is protected by copyright. All rights reserved.