Micro raman spectroscopy

Ten freshly extracted, non-carious human third molars were prepared as described in In situ zymography. The teeth were divided into two groups. The experimental group was preconditioned with 8 mg ml⁻¹ G4-PAMAM-COOH for 1 min after etching with the 35% phosphoric acid gel, and the control group was pre-treated with deionized water. The resulting resin–dentine discs were sectioned into several slices (each 1 mm thick). Two slices in the middle of each disc were selected to analyse the degree of conversion (DC). The DC of each group (n = 6) was assessed by micro-Raman spectroscopy at 785 nm wavelength (Renishaw inVia, UK). A microscope (Leica DM/LM optical microscope; Leica, Wetzlar, Germany) was connected to micro-Raman spectroscopy. With the help of the microscope, a laser beam generating an approximately 1 µm spot focused on the intertubular regions of the resin–dentine interface. The spectra were acquired in line scans and calculated using the following formula [43 (link)]: $\mathrm{DC}\text{\%}=\left(1-\frac{R_{\mathrm{cured}}}{R_{\mathrm{uncured}}}\right)\times 100\text{\%},$ where R represents the ratio between the peak intensities at 1640 cm⁻¹ and at 1610 cm⁻¹ of the light-cured adhesive at the resin–dentine interface and uncured adhesive within the quartz capillary siphon, respectively.