Raman spectroscopy on dentin/resin interface of lased and unlased dental samples

Cavities in human teeth were fabricated by means of Er:YAG laser and compared with samples processed by using conventional drill. The cavities of lased and unlased samples were cured with two different composite resins (Bis-GMA vs PEX) to investigate differences in their adhesion properties. Morphological characterization of the sample surfaces by SEM analysis was performed. The same samples were then examined by micro-Raman spectroscopy by using He-Ne laser visible light excitation, in order to characterize the dentin/resin interfaces. The Raman spectra exhibited typical peaks of dentine. Resin contributions to the Raman spectra were also detected and have been used to monitor the interface properties of the boundary region. The dependence of the Raman spectrum on spatial position has been monitored. In both lased and unlased samples the PEX diffusion in dentine is limited in a region of order of 10 micrometer depth. A larger interdiffusion region is observed at the boundary of dentine and Bis-GMA resin.