Simulation of conversion profiles inside a thick dental material photopolymerized in the presence of nanofillers

Abstract

In dental composites, the presence of inorganic fillers in the organic matrix leads to a light-scattering phenomenon that modifies the light intensity and, consequently, the ultimate polymerization yield. In this study, we aimed to characterize the impact of light scattering on the photopolymerization profiles inside thick materials. First, the photopolymerization kinetics of dental composites containing alumina or zirconia nanofillers were studied. An optimal formulation based on 75 wt% Bis-GMA, 25 wt% triethyleneglycoldimethacrylate and 1 wt% camphorquinone/dimethylaminoethylmethacrylate (1/1) was determined. The compatibility between the organic matrix and the fillers was enhanced by grafting a silane coupling agent onto the surfaces of the nanoparticles. This grafting improved the mechanical properties of the final composites without modifying the photopolymerization kinetics. The presence of nanofillers leads to a light-scattering phenomenon that influences the photoinitiated polymerization yield inside the composite. Thus, to characterize this phenomenon, a four-flux radiative transfer theory was applied to calculate the decrease in the light intensity crossing the dental composite. The conversion profiles were then calculated and compared with experimental ones. © 2013 The Society of Polymer Science, Japan (SPSJ) All rights reserved.