Does Calculus Confound PRS and OCT Detection of Early Caries?

New caries detection methods are emerging, however the results of these tools can be compromised by some components of the oral environment. Polarized Raman spectroscopy (PRS) and optical coherence tomography (OCT) can distinguish sound enamel from caries lesions in vitro, however the effect of calculus on these techniques has not yet been examined. OBJECTIVE: To determine whether calculus is a confounding factor affecting early caries detection with PRS and OCT. METHODS: Extracted human teeth were first clinically examined for sound enamel (n=13), white spot lesions (WSLs, n=13), and calculus (n=8 teeth, 15 surfaces). PRS and OCT measurements were acquired and results from teeth with calculus were compared to those with sound enamel and WSLs. Raman depolarization ratios (£l) were calculated and the OCT images analyzed. Raman spectra were also acquired from four inorganic components of calculus: brushite, hydroxyapatite, octacalcium phosphate and whitlockite. Raman peak positions of these spectra were compared to those of sound enamel, WSLs, and calculus. RESULTS: Raman depolarization ratios were able to differentiate between sound enamel (ƒâ=0.10+/-0.04) and WSLs (ƒâ=0.40+/-0.12). However, these ratios alone could not differentiate between WSLs and calculus (ƒâ=0.44+/-0.16). Using Raman peak positions calculus (961.9 cm-1) can be distinguished from sound enamel (959.7 cm-1) and WSLs (959.7 cm-1). OCT imaging was able to differentiate WSLs and sound enamel based on the light back-scattering intensity and characteristic triangular shape of WSLs. Calculus deposits were clearly recognizable on OCT images enabling calculus to be distinguished from sound enamel and WSLs. CONCLUSION: Combining PRS and OCT allows for differentiation of sound enamel, WSLs and calculus. These methods have potential as new technologies for detection of early caries with high specificity and sensitivity even in the presence of calculus.

Funding support provided in part from CIHR-NORTH, CIHR-IMHA and NIH-NIDCR (R01DE017889).