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

Abstract

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 necessary for the enhanced resolution of the surface structure of caries lesions. This study demonstrated that PS-OCT is well suited for the imaging of interproximal and occlusal caries, early root caries, and for imaging decay under composite fillings. Longitudinal measurements of the reflected light intensity in the orthogonal polarization state from the area of simulated caries lesions linearly correlated with the square root of time of demineralization indicating that PS-OCT is well suited for monitoring changes in enamel mineralization over time.

Dental Applications of Optical Coherence Tomography (OCT) in Cariology

“…In vitro studies showed an adequate to strong agreement, when SS-or SD-OCT were compared to histology [29,42,43], confocal microscopy, X-ray microtomography, or transverse microradiography and a diagnostic superiority compared to bitewing radiography [44] (Figures 1, 2 and 5-11 and 14). Image contrast and the spatial separation of the lesion body versus sound enamel can be further enhanced using polarization-sensitive OCT [45]. Additionally, variation of the imaging beam angle by using different positions of the OCT probe can improve the detectability of non-cavitated occlusal carious lesions (Figure 8).…”

“…The sensitivity of the method can be increased among others by increasing the integration time (A-scan rate) or using coupling media [46] to minimize surface reflections, which can also contribute to enhance the image contrast ( Figure 9). Image contrast and the spatial separation of the lesion body versus sound enamel can be further enhanced using polarization-sensitive OCT [45]. Additionally, variation of the imaging beam angle by using different positions of the OCT probe can improve the detectability of non-cavitated occlusal carious lesions (Figure 8).…”

Use of new minimum intervention dentistry technologies in caries management

“…Monitoring in vivo carious lesion changes could be helpful with this device. [34][35][36] A combination of near infrared radiation (NIR) imaging with PS-OCT was also described to acquire depthresolved images. Combining this technology with a short-pulsed CO 2 laser ablation system would allow for the selective removal of dental caries.…”

Early caries detection using optical coherence tomography: a review of the literature

“…In 2002, Fried et al demonstrated that PS-OCT was well-suited for monitoring changes in enamel demineralization over a time period of 1 to 14 days. 65 After that, a series of studies using an artificial caries model and PS-OCT was performed to evaluate caries under composite sealants and restorations, the severity of interproximal caries lesions, occlusal surface caries, remineralization of the lesion, inhibition of demineralization by anticaries tools such as fluoride or lasers, demineralization of enamel by CO2 lasers, demineralization of exposed root surfaces, and de-/re-mineralization of dentin. 7,[66][67][68][69][70][71][72][73][74][75] In addition, this group compared the near-infrared (NIR) transillumination to PS-OCT and combined these methods with other optical techniques into image-guided laser ablation systems.…”