Measurement of the severity of natural smooth surface (interproximal) caries lesions with polarization sensitive optical coherence tomography

Abstract

Previous studies have demonstrated that polarization sensitive optical coherence tomography (PS-OCT) can be used to image early dental caries. The purpose of this study was to compare the measured reflectivity of natural caries lesions found on smooth surfaces (interproximal lesions) with the mineral loss measured using digital microradiography (DM) in order to determine if PS-OCT can be used as a non-destructive method to measure the severity of dental decay and resolve the internal structure of caries lesions. A PS-OCT system operating at 1,310 nm was used to acquire polarization resolved images of natural white spot lesions and pigmented lesions on the smooth surfaces of extracted teeth. The integrated reflectivity from lesion areas was compared to polarized light microscopic images (PLM) and to the integrated mineral loss from the same lesion area measured using high resolution DM. The frequently complex internal structure of caries lesions could be resolved with PS-OCT. Such structural information is potentially useful for determining whether or not the lesion is active and progressing or whether it has become arrested and remineralized and does not require intervention. There was a strong correlation between the integrated mineral loss of the caries lesions measured using DM and the integrated reflectivity in the perpendicular polarization axis of the PS-OCT system. The integrated reflectivity in the perpendicular polarization channel can be used to represent the severity of demineralization in natural early caries lesions. Therefore, PS-OCT has considerable potential as a non-destructive clinical probe of early caries lesions to assess their severity, monitor their progression over-time and potentially assess lesion activity.