Vicker's hardness and Raman spectroscopy evaluation of a dental composite cured by an argon laser and a halogen lamp.

We present the results of the Vicker's hardness test and the use of near-infrared Raman spectroscopy (RS) to measure in vitro the degree of conversion (DC) of a bis(phenol)-A-glycidyl-dimethacrylate-based composite resin, photoactivated by both a halogen lamp (power density=478 mW/cm(2); 8-mm diameter spot) and an argon laser (power density=625 mW/cm(2); 7-mm diameter spot). The degree of conversion was estimated by analyzing the relative intensities between the aromatic C=C stretching Raman mode at 1610 cm(-1) and the methacrylate C=C stretching Raman mode (1640 cm(-1)) on top and bottom surfaces. For the hardness evaluation, the samples were embedded in polyester resin and three indentations with a 50-g load for 10 s were made on the top surface. The higher relative DC values achieved by the photoactivation of a composite resin by the argon laser suggest a better biocompatibility in the bottom surface. The correlation test showed that the higher Vicker's hardness number (VHN) values were associated with higher DC values. The derivative analysis showed a greater curing rate from 5 to 20 s of exposure. The comparison of VHN and DC values with both light sources at each curing time showed that a small change in conversion is related to a large change in hardness. Raman spectroscopy is more sensitive to changes in the first stages of curing reaction than later ones, and the Vicker's hardness assay is more sensitive to changes in the last stages.

Raman spectroscopy validation of DIAGNOdent-assisted fluorescence readings on tibial fractures treated with laser phototherapy, BMPs, guided bone regeneration, and miniplates.

OBJECTIVES: We aimed to assess through Raman spectroscopy and fluorescence the levels of calcium hydroxyapatite (CHA) and lipids and proteins in complete fractures treated with internal rigid fixation (IRF) treated or not with laser phototherapy (LPT) and associated or not with bone morphogenetic proteins (BMPs) and guided bone regeneration (GBR). BACKGROUND: Fractures have different etiologies and treatments and may be associated with bone losses. LPT has been shown to improve bone healing. METHODS: Tibial fractures were created on 15 animals and divided into five groups. LPT started immediately after surgery, repeated at 48-h intervals. Animal death occurred after 30 days. RESULTS: Raman spectroscopy and fluorescence were performed at the surface. Fluorescence data of group IRF + LPT + Biomaterial showed similar readings to those of the group IRF-no bone loss. Significant differences were seen between groups IRF + LPT + Biomaterial and IRF + LPT; IRF + LPT + Biomaterial; and IRF + Biomaterial; and between IRF + LPT + Biomaterial and IRF. CH groups of lipids and proteins readings showed decreased levels of organic components in subjects treated with the association of LPT, biomaterial, and GBR. Pearson correlation showed that fluorescence readings of both CHA and CH groups of lipids and proteins correlated negatively with the Raman data. CONCLUSIONS: The use of both methods indicates that the use of the biomaterials associated with infrared LPT resulted in a more-advanced and higher quality of bone repair in fractures treated with miniplates and that the DIAGNOdent may be used to perform optical biopsy on bone.

Dentin evaluation after Nd:YAG laser irradiation using short and long pulses.

OBJECTIVE: Several reports have demonstrated the advantages of using the Nd:YAG laser to reduce dentin permeability by melting the dentin surface. A comparative study using different pulse durations can be useful to obtain further information about the laser-hard tissue interaction. MATERIALS AND METHODS: The present study pursues the evaluation of the morphological and chemical changes in human dentin surface resulting from Nd:YAG laser (lambda = 1064 nm) irradiation, with a total energy of 0.9 J distributed in 1, 2, 3, and 6 pulses with different pulse durations to promote surface melting and dentinal tubule occlusion. After irradiation, the samples were submitted to scanning electron microscopy (SEM) analysis for morphological study and energy-dispersive spectrometry (EDS) analysis for evaluation of the concentration of calcium and phosphorous in the melted layer. RESULTS: SEM analysis of the irradiated dentin surface showed surface structural changes due to laser irradiation, where the morphological changes are dependent on the laser pulse duration. EDS analysis showed an increase of calcium and phosphorous concentrations after Nd:YAG laser exposure, but no correlation with the number of pulses or pulse duration was found. CONCLUSION: Our results suggest that longer interaction times resulted in more evident effects with more melted substrate than shorter pulses, and in both cases the resultant melted layer contains a greater concentration of inorganic substances than non-irradiated dentin.