Raman Spectroscopy in Dental Research: A Short Review of Recent Studies

The Raman spectroscopic technique enables us to obtain vibrational (IR and far-IR) spectra of minerals by analyzing scattered light caused by (visible or near-visible) monochromatic laser excitation. The method possesses several advantages over IR absorption, including simple sample preparation, easy spectral/band analysis, and linear-response to mineral/chemical concentrations. In micro-Raman spectrometer systems, samples are positioned under an optical microscope, and specimens can be scanned with a lateral resolution (- 1 mm). In this paper, recent applications of micro-Raman spectroscopy and near-infrared Fourier transform Raman spectroscopy in the study of dental hard tissues and of calculus are reviewed. Special attention is given to mineral components in enamel, dentin, and calculus, and to calcium fluoride formed in/on enamel. The results from the use of an Ar+-laser/grating-based micro-Raman spectrometer show that: CaF2 formed in/on enamel by APF treatment is detectable and different from pure CaF2; and with the technique, the crystallite orientation in enamel can be determined. A Raman spectrometer based on Fourier transform and a diode-laser-pumped Nd:YAG laser (1.06 mm) can be used to obtain fluorescence-free Raman signals from biological materials, and identification of mineral components present in dental calculus is possible.

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Multichannel Fourier Transform Raman Spectroscopy: Combining the Advantages of CCDs with Interferometry

Applied Spectroscopy ◽

10.1366/0003702963905060 ◽

1996 ◽

Vol 50 (9) ◽

pp. 1209-1214 ◽

Cited By ~ 17

Author(s):

Jun Zhao ◽

Richard L. McCreery

Keyword(s):

Raman Spectroscopy ◽

Fourier Transform ◽

Near Infrared ◽

Signal To Noise Ratio ◽

Scattered Light ◽

Infrared Region ◽

Integration Time ◽

Beam Diameter ◽

Common Path ◽

Fourier Transform Raman Spectroscopy

A common-path (Sagnac) interferometer combined with a charge-coupled device (CCD) was evaluated for Raman spectroscopy in the near-infrared region. A spatial interferogram of the scattered light was projected onto the face of the CCD, and a Fourier transform of the intensity vs. pixel data yielded a Raman spectrum. This multichannel Fourier transform (MCFT) technique retains several advantages of FT spectroscopy, including high throughput, excellent frequency precision, and wide spectral coverage, while also retaining the multichannel, shot-noise-limited operation of the CCD. The signal-to-noise ratio (SNR) for the MCFT system was comparable to that for a dispersive spectrometer for the same laser power and integration time, and its frequency and intensity stability were excellent. Resolution is dictated by the number of CCD pixels, and was 25 cm−1 for the initial MCFT system. In addition to stability, a possibly important feature of the MCFT spectrometer is its large Ail product ( etendue), which results in a signal which is independent of laser beam diameter over the range of 60 μm to 1.3 mm.

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