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Objectives: The aim of this paper was to evaluate a transillumination (TI) system using near-infrared (NIR) light and bitewing radiographs for the detection of early approximal enamel caries lesions. Methods: Mesiodistal sections of teeth (n 5 14) were cut with various thicknesses from 1.5 mm to 4.75 mm. Both sides of each section were included, 17 approximal surfaces with natural enamel caries and 11 surfaces considered intact. The approximal surfaces were illuminated by NIR light and X-ray. Captured images were analysed by two calibrated specialists in radiology, and re-analysed after 6 months using stereomicroscope images as a gold standard. Results: The interexaminer reliability (Kappa test statistic) for the NIR TI technique showed moderate agreement on first (0.55) and second (0.48) evaluation, and low agreement for bitewing radiographs on first (0.26) and second (0.32) evaluation. In terms of accuracy, the sensitivity for the NIR TI system was 0.88 and the specificity was 0.72. For the bitewing radiographs the sensitivity ranged from 0.35 to 0.53 and the specificity ranged from 0.50 to 0.72. Conclusion: In the same samples and conditions tested, NIR TI images showed reliability and the enamel caries surfaces were better identified than on dental radiographs.

Spatial modification of a Gaussian beam by reflection on a surface of a high-absorbing material is investigated experimentally. A theoretical description in a geometrical-optics approach is given. The usefulness and sensitivity of the method for applications in measuring laser induced surface deformation and Kerr-like nonlinear coefficients is discussed.

We report measurements of the nonlinear (NL) refractive index n2 of lead-germanium films (LGFs) containing Cu and Cu2O nanoparticles (NPs). The thermally managed eclipse Z-scan technique with 150fs pulses from a laser operating at 800nm was used. The NL refractive index measured, n2=6.3×10−12cm2∕W has electronic origin and the NL absorption coefficient α2 is smaller than 660cm∕GW. The figure of merit n2∕λα2 is enhanced by more than two orders of magnitude in comparison with the result for the LGFs without the copper based NPs.