Photopolymerization of a commercial dental resin has been investigated by 1D and 3D conventional MRI, at different magnetic fields. The containers were of several materials, which included human molar teeth to mimic in vivo conditions. Visible light was applied to the resin-air interface and the spatial distribution of unreacted monomers was obtained. By the end of the irradiation period, a non-cured polymer layer (thickness similar to200 mum) remained at the surface. Delayed polymerization of the resin in contact with the container was especially observed in tooth occlusal cavities. Polymerization kinetics of the bulk was obtained from 3D MRI data. (C) 2004 Elsevier Ltd. All rights reserved.