Emerging Dental Applications of Raman Spectroscopy - Emerging Raman Applications and Techniques in Biomedical and Pharmaceutical Fields - page 269

Fig. 11.6. Bar graphs of the mean Raman depolarization ratio calculated from
the parallel- and cross-polarized intensities of the 959 cm − 1 PO 4 3 − peak. Data were
obtained from 47 (sound) and 27 (caries) PRS measurements on 23 extracted teeth.
Student's t -test analysis reveal p< 0.001. Error bars show standard deviation
carbonated hydroxyapatite enamel crystals from demineralization is respon-
sible for the spectral changes observed with PRS. The intensity changes ob-
served suggests that the depolarization ratio could be a clinically useful pa-
rameter for in vivo measurements.
11.7 Towards Clinical Utility and Clinical Validation
The initial studies described above were conducted on Raman microspectrom-
eters on extracted human teeth. In order to translate this research from the
laboratory bench to the dental chair side, the next step it is to develop ded-
icated systems for clinical use. A key element to this development is the use
of fibre-optic probes to allow measurements in vivo. We recently reported a
study in which optical fibres were used for PRS measurements [48]. Although
not yet fully realized into a dental probe, this study demonstrated the design
and feasibility of acquiring parallel- and cross-polarized Raman spectra via a
bifurcated optical fibre whose distal terminal has the two fibres aligned verti-
cally for simultaneously collecting spectra from the two polarization channels
on a 2D CCD array. Simultaneous data acquisition will allow for more rapid
measurement times in vivo.
To examine the clinical utility of our method, we have conducted vari-
ous preliminary studies in which we have shown using artificial caries models
of demineralization and remineralization that the ρ 959 depolarization ratio
of PRS measurements enables us to not only follow the progression and ex-
tent/severity of early caries development, but also to monitor the repair pro-
cess involving fluoride treatment [49, 50]. In addition, other initial studies have