FT-Raman spectroscopy, µ-EDXRF spectrometry, and microhardness analysis of the dentin of primary and permanent teeth.

The chemical compositions (organic and inorganic contents) and mechanical behaviors of the dentin of permanent and deciduous teeth were analyzed and compared using X-ray fluorescence spectrometry (µ-EDXRF) Fourier transform Raman spectroscopy (FT-Raman) and a microhardness test (HD). Healthy fresh human primary and permanent molars (n = 10) were selected, The buccal surfaces facing upwards were stabilized in an acrylic plate, flattened, polished, and submitted to the µ-EDXRF, FT-Raman, and HD analysis. The results of the analysis were subjected to ANOVAs and Mann-Whitney U/Student's t multiple comparisons tests. The data showed similar values for the dentin of the primary and permanent teeth in P content, organic content (amide I peak), inorganic content ( PO43- - 430 and 590), and microhardness, Nevertheless, Ca content and Ca/P weight ratio were higher, and the CO32- peak was lower in the dentin of the permanent teeth compared to primary teeth. It be concluded that despite permanent teeth showed more Ca element, both substrates showed similar behavior of chemical and physical properties.

Degree of conversion of composite resin: a Raman study.

OBJECTIVE: Near infrared Raman spectroscopy (RS) was used to monitor, in vitro, the degree of conversion (DC) of composite resins (Z100, 3M), photoactivated by both the halogen lamp and the argon laser beam. BACKGROUND DATA: Several methods were used to study the alterations of composite resins. Vibration methods such as RS allow a precise assessment of the depth of polymerization and the degree of conversion of composite resins. MATERIALS AND METHODS: Sixty circular blocks of resin (7 mm x 2.5 mm) were cured using a halogen light source (n=30, lambda=400-500 nm, power density=478 mW/cm2) or an argon laser beam (n=30, lambda=488 nm, power density=625 mW/cm2) using the same irradiation time (5, 10, 20, 30, 40, and 60 sec). The directly irradiated (top) and the non-irradiated (bottom) surfaces were analyzed immediately after curing by Raman spectroscopy. RESULTS: The Raman results show systematic changes of the relative intensities between the peaks at 1610 (aromatic C=C stretching mode) and the 1640 cm(-1) (methacrylate C=C stretching mode), as a function of irradiation time. After 60 sec of irradiation time, the maximum degree of conversion reached for the samples cured either by the argon laser or halogen lamp was 66.4% and 62.2%, respectively. CONCLUSION: The argon laser was more effective and showed better biocompatibility, with less residual monomer in the bottom (2.5 mm). These results show that RS can be used as an effective method to study the degree of conversion of composite resins.