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The purpose of this study was to investigate the possibility of postponing restorative intervention of manifest occlusal caries in young, permanent dentition by non-invasive sealing. This RCT-designed study included 521 occlusal lesions in 521 patients aged 6 to 17 y. Based on clinical and radiographic assessments, all lesions required restorative treatment. After randomization (ratio 2:1), 368 resin sealings and 153 composite-resin restorations were performed by 68 dentists in 9 municipalities. The primary aims were to 1) analyze survival of sealings until replacement by restoration, 2) compare longevity of sealings and restorations until retreatments, and 3) compare effectiveness of sealings and restorations to halt caries progression in sealed lesions and beneath restorations. Furthermore, we aimed to identify factors influencing longevity and the effectiveness of sealings and restorations. Treatments were annually controlled, clinically and radiographically. After 7 y, the drop out rate was 8%, and 54% of the treatments were completed due to age. Of the sealings, 48% were retreated, including 31% replaced by restorations; 12% were still functioning. Of the restorations, 7% were repaired/renewed and 20% were still functioning. No endodontics was performed. Kaplan-Meier and Cox regression survival analyses were performed on 341 sealings and 152 restorations in first and second molar teeth. The 7-y survival was 37% (CI, 29% to 45%) for sealings and 91% (CI, 85% to 96%) for restorations (P < 0.001). The median survival time for sealings not replaced by restorations was 7.3 y (CI, 6.4 y to NA). Survival of sealings was increased in patients with low caries risk and/or excellent oral hygiene, second molars compared with first molars, and lesions not extending the middle one-third of the dentin. Survival of sealings was not influenced by municipality, sex, eruption stage or clinical surface cavitation. The results underline that it is possible to postpone or avoid restorative intervention of occlusal dentin caries lesions in young permanent teeth by non-invasive sealing. Knowledge Transfer Statement: The first restoration can ultimately be fatal for a young permanent tooth. A restoration may not be the final treatment but the start of an ongoing treatment with still more loss of tooth substance. The present study shows the possibility of treating occlusal dentin caries lesions with non-invasive resin sealings instead of conventional resin composite restorations in children and adolescents. Improved oral health can be expected.
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We address curved IR screens for multiwavelength systems. To first-order of the approximation, a curved screen may be viewed as composed of many local flat screens. On the other hand, the validity of such an approximation is not clear a priori. We provide experiments and simulations to show that such an approximation works well for cylindrically curved IR screens while monitoring their peak transmission as a function of the screen curvature.
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Metallo-dielectric photonic crystals with cubic symmetries have been studied here both experimentally and theoretically in the millimeter wavelength region (15-60 mm). In a direct analogy to linear systems, we considered the three-dimensional lattices as a stack of two-dimensional resonating screens. The overall three-dimensional structure was introduced in the calculation through a structural phase. Such an approach proved useful in understanding the related mode propagation and guided us in a study of the transition between cubic and centered body cubic symmetries.
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The efficiency of a wave-front-dividing interferometer with circular symmetric sets of reflectors is studied and compared with that of a lamellar grating. The circular-reflector interferometer shows more efficient modulation over larger spectral regions in the far IR than the lamellar grating does. In contrast to Michelson and Martin-Puplett interferometers no beam splitters are employed.
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A photolithographic process has been used to form cross-shaped patterns in 3-µm-thick nickel foils. Patterns with cross arm dimensions in the 10-20-µm range, and with periodicities in the 16-26-µm range, yield self-resonant bandpass filters for wavelengths in the 20-25-µm region. Transmittances as high as 80% were achieved with center wavelength-to-bandwidth ratios (λ(R)/Δλ) of ~5. We present a simple empirical formula that relates the wavelength of peak transmittance, or resonant frequency, with cross dimensions and periodicity.
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Interferometers of the Michelson or Mach-Zehnder type are designed as array interferometers. The number of array channels is equal to the number of points needed for an interferogram for Fourier transformation. Similarly one may use an array of step gratings with each grating having a different step height and producing one point of the interferogram. These interferometers, which do not have moving parts, use all the incident light, and the interferogram is instantly produced for real-time spectroscopy.
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We describe what is to our knowledge the first instrument specifically designed for use with infrared synchrotron radiation that takes advantage of the spatial coherence of this radiation. Beam splitting is achieved by wave-front division. We show data taken with the instrument over the wavelength region from 10 to 1000 microm (1-mm wavelengths) and discuss the advantages of this instrument over a conventional one.
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The radiant output of a noise tube (C. P. Clare Model TN-167), designed for the 90-140-GHz (3.3-2.1-mm) frequency range, has been compared with that from mercury lamps over the wavelength region from 0.4 to ~6 mm. Lamellar grating and Michelson Fourier transform spectrometers were used in conjunction with He cooled bolometers of NEP from 10(-12) to 10(-14) W/(H(2))(1/2) to measure relative spectral irradiance. With this instrumental arrangement, the radiant power emitted by the noise tube was observed to be less than that from a mercury lamp, at least to a 3-mm wavelength, but it produced less source noise than an ac operated mercury lamp. When the noise tube operating current was reduced, the spectral irradiance peak shifted to longer wavelengths.
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The optical transmission characteristics of electroformed metal grids with inductive and capacitive cross patterns have been investigated in the far-infrared spectral region. The transmission characteristics of one-and two-grid devices are represented by transmission line theory parameters. Results are used to suggest construction guidelines for two-grid bandpass filters.
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The real and imaginary parts of the complex index of refraction have been measured in the 3-14-microm region for nine black powders. Data were obtained from specular reflection measurements on pressed powder disks. A vintage prism spectrometer was considerably modified for this study. Polarized radiation, detected with a cooled photoconductor, was used to generate isoreflectance curves from which the optical properties were extracted. With the exception of a bone charcoal sample, the optical constants of the black powders exhibited no spectral features in the wavelength range considered. Measured values were generally in agreement with published data on similar materials. Surface effects were found not to produce a significant limitation on the results of our method.
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A Michelson-type Fourier transform spectrometer has been constructed for high resolution work in the far ir. The instrument has a theoretical resolution of 0.007 cm(-1) and can be used with a tunable band pass filter system for the reduction of sampling points in a specific spectral region. Separations of 0.05 cm(-1) in the inversion spectrum of NH(3) in the 200-cm(-1) spectral region have been observed with about 1000 sampling points and splittings of 0.04 cm(-1) in the NO(2) spectrum at about 100 cm(-1).
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Capacitive meshes for far ir, low pass filters are prepared from Cu layers on 2.5 micro plastic film. The properties of these meshes of different mesh constants g with their different combinations in two-mesh, fourmesh, and eight-mesh filters are studied in the spectral region 160 cm(-1) to 10 cm(-1) by the use of a grating spectrometer. The applications of these meshes as low pass filters in the far ir spectral region in a grating spectrometer are described.
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Transmittance and reflectance measurements on wirecloth and electroformed metallic meshes are presented in the region 0.01
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A simplified method for the fabrication of crystal powder transmission filters is reported. Transmission filter combinations are described for the 300-18 cm(-1) spectral region. The application of these filters in a small grating spectrometer is demonstrated by water vapor spectra.