Micro-Raman spectroscopy and E-SEM analysis of hybrid layer at the dentine/resin interface of three different composite restorative resins

The formation of a hybrid layer at the dentin/resin interface is a critical point in the curative processes. New restorative materials are currently under investigation in order to improve the characteristics of this interface layer. In this paper micro-Raman spectroscopy and Environmental Scanning Electron Microscope (E-SEM) analysis have been performed to investigate the interface properties of three different restorative materials. The experimental investigation has been performed on tooth cavities prepared both by Er:YAG laser ablation and by conventional diamond bur. Laser prepared cavities were realized using 100 ms pulsed light beam with energy of 350 mJ, at a frequency of 20 Hz. The cavities were filled with three different composites: True-Vitality (Den-Mat), Enamel Plus (Micerium), Supreme (3M). The treated samples were sectioned perpendicularly to the exposed dentin surface and the morphological characterization of the samples was performed by means of E-SEM operating in wet mode. This equipment permits to obtain a high-resolution image of surface without conductive coating process. The same samples were then examined by micro-Raman spectroscopy that has already shown its validity in the study of dentin/resin interfaces.