The study of a commercial dental resin by ¹H stray-field magnetic resonance imaging

A dentine/enamel resin containing methacrylate monomers, included in a new generation adhesive system, was used to evaluate the potentialities of recent nuclear magnetic resonance imaging (MRI) techniques to obtain spatially-resolved information on photo-polymerization reaction and subsequent polymerization shrinkage. ¹H stray-field (STRAFI)-MRI one-dimensional images (1D profiles) of visible-light cured resins were obtained in the presence of oxygen from the atmosphere, and the variation of magnetization with irradiation time was recorded for each resin slice. The polymerization shrinkage was obtained from 1D profiles. The spatial distribution of the unreacted methyl methacrylate groups was obtained from 3D STRAFI experiments. In particular, the thickness of the surface remaining unpolymerised was measured.