Micro-Raman Spectroscopy and Imaging of the DEJ and CDJ

Objectives: Raman spectroscopy (RS) and imaging are used to investigate the microstructure of dental hard tissue at the molecular level. The evaluation of the width of the dentino-enamel-junction (DEJ) and the cemento-dentin junction (CDJ) was conducted using RS with respect to the concentration of collagen in enamel, DEJ and dentin. Methods: Three caries free human third molars were cut bucco-lingually, to obtain 2 mm thick slices exposing the DEJ and CDJ. The specimens were polished through 0.05 µm. Raman spectra were obtained in intervals, crossing the interfaces in 0.5 µm steps (total length=20 µm) on a computer-controlled X-Y recorder for wave numbers between 2200 to 3600 cm –1. Raman spectra were obtained at each interval. Spectra were acquired with laser excitations at 532 nm and 633 nm. C-H stretching modes at 2881, 2948, 2923 and 2988 cm–1, representing collagen in dental hard tissue were examined. The CDJ was evaluated with the same parameters as the DEJ. Results: Generally the luminescence of enamel was higher than dentin and cementum. The C-H stretching mode peaks decreased monotonically from dentin to enamel within 8.6 (+/-1.1) µm width at the DEJ. No significant changes in C-H stretching modes were observed at the CDJ. However, a highly luminescence zone of about 30 mm width was detected at this junction. Conclusion: A gradual change in collagen concentration at the DEJ was observed. The width of the zone is in accord with the change in elastic modulus and hardness previously reported by our group using AFM based nano-indentation techniques.(JBMR: 54, 2001) NIH/NIDCR Grant P01DE 09859. schulze@itsa.ucsf.edu