Photopolymerization kinetics of dimethacrylate-based light-cured dental resins

摘要

The influence of certain factors [structureudand concentration of tertiary amines as coinitiators, monomerudcomposition, presence of inorganic pigments, and incidentudlight intensity (I0)] on the polymerization rates (Rp),udpolymerization quantum yields, and conversions of bisphenoludA–bis(glycidyl methacrylate) (Bis-GMA)/triethyleneudglycol dimethacrylate based resins was studied. The initialudrate of bulk polymerization increased and the final conversionuddecreased with the content of Bis-GMA in the mixture.udIn contrast, it was established that, for all monomer compositions,udthe Rp grew when increasing the I0, the Rp beinguddirectly proportional to the square root of I0. Such behaviorudis in agreement with the well-known kinetic expression forudthe ideal radical photoinitiated polymerization in solution ofudmonofunctional monomers, in spite of the complexity of theuddimethacrylate mixtures that were studied. Both the structureudand the concentration of reducing amine affected theudefficiency of the initiator system and therefore the kineticudbehavior of polymerization of these formulations under irradiation.udThe rate of polymerization increased with theudincrease of coinitiator concentration over the interval ofud0–1%, but later it diminished when increasing the amineudcontent, suggesting that the excess coinitiator retards theudpolymerization process. The study of the photoreduction ofudcamphorquinone in the presence of different amines showedudthat the efficiency of the coinitiator depends not only on itsudability to photoreduce camphorquinone, forming amine-derivedudradicals, but also on the reactivity of these radicalsudtoward the initiation of acrylic monomer polymerization.