Emerging Dental Applications of Raman Spectroscopy - Emerging Raman Applications and Techniques in Biomedical and Pharmaceutical Fields - page 275

as a means of detecting early carious lesions [42]. An ordered hydroxyapatite
matrix shows a strongly polarization dependent

ν 1 PO 4 − 3 stretch while the
ν 1 PO 4 − 3 stretch shows a reduced polarization dependence when the ordered
matrix is disrupted. Early caries formation disrupts the structure of the hy-
droxyapatite matrix which in turn increases the depolarization ratio of the ν 1

mode of the PO 4 − 3 peak.
Though a sensitive marker, polarized Raman spectroscopy on its own has
limited clinical utility due to the point-by-point nature of measurement. To
overcome this limitation, we have coupled PRS with optical coherence tomog-
raphy which will serve as an initial screening tool that provides morphological
images that the dental clinician can readily relate to as well as provide clin-
ically relevant parameters such as lesion shape, depth and extent. As with
all diagnostic methods, this light backscattering approach too can suffer from
false-positive readings such as in the presence of hypocalcification. Where
OCT flags regions of suspicious carious activity, PRS is used to provide bio-
chemical confirmation of the presence of a carious lesion. In so doing the
OCT-PRS method will provide high sensitivity and high specificity for early
caries detection and monitoring. Both OCT and PRS are readily adapted for
fibre-optic measurements thus allowing its use in vivo. Research is underway
to develop a combined OCT-PRS intra-oral probe for use in the dental clinic.
In so doing, research that began as classical laboratory bench studies can be
translated into use at the dental clinic chair side. The multi-modal approach
involving OCT and PRS provides pieces of evidence that the clinician can use
in formulating a diagnostic assessment for improved and effective patient oral
health care.

Acknowledgements

Research funding has been derived in part from past and current grants from
the Manitoba Medical Service Foundation, Canadian Institutes of Health
Research - Institute of Musculoskeletal Health and Arthritis, and the US
National Institutes of Health - National Institute of Dental and Craniofacial
Research (#R01DE017889). We thank our clinical collaborators, Dr. Cecilia
Dong (Faculty of Dentistry, U. Manitoba) and Dr. Blaine Cleghorn (Faculty
of Dentistry, Dalhousie U.) for insightful discussions and clinical assessments.
We also thank the staff and students of the Dental Clinics at U. Manitoba
and at Dalhousie U. for assistance with tooth collection.

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