Imaging caries lesions and lesion progression with polarization sensitive optical coherence tomography

New diagnostic tools are needed for the characterization of dental caries in the early stages of development. If carious lesions are detected early enough, they can be arrested without the need for surgical intervention. The objective of this study was to demonstrate that polarization sensitive optical coherence tomography (PS-OCT) can be used for the imaging of early caries lesions and for the monitoring of lesion progression over time. High-resolution polarization resolved images were acquired of natural caries lesions and simulated caries lesions of varying severity created over time periods of 1 to 14 days. Linearly polarized light was incident on the tooth samples and the reflected intensity in both orthogonal polarizations was measured. PS-OCT was invaluable for removing the confounding influence of surface reflections and native birefringence and for resolving the surface structure of caries lesions. This study demonstrated that PS-OCT is well suited for the resolution of interproximal and occlusal caries, early root caries, and secondary caries around composite fillings. Longitudinal measurements of lesion progression established a strong correlation (p<0.001) between the reflected light from the lesion area and the square root of time indicating that PS-OCT is well suited for monitoring changes in enamel mineralization over time.