Imaging Natural Occlusal Caries Lesions with Optical Coherence Tomography

Abstract

Several studies have demonstrated that polarization-sensitive optical coherence tomography (PS-OCT) can be used to nondestructively measure the severity of demineralization in the important occlusal surfaces. The purpose of this study was to assess the potential of PS-OCT and OCT methods for the measurement of the depth of natural occlusal carious lesions. Teeth were screened for potential occlusal lesions using near infrared imaging (NIR). A PS-OCT system operating at 1310-nm was used to acquire polarization resolved images of the area of interest on the occlusal surface. The teeth were serial sectioned to 200 μm thickness and examined with polarized light microscopy (PLM) and Transverse Microradiography (TMR) for comparison. The lesion depth measured nondestructively with PS-OCT was compared to the lesion depth measured with PLM and TMR to assess the performance of these methods and determine if polarization sensitivity is required. The lesion depth measured using OCT correlated well with the lesion depths measured with TMR and PLM. Although polarization sensitivity provided better contrast it was not necessary to have polarization sensitivity to identify deep occlusal lesions.

Fig. 1

A photograph series of a prepared sample mounted on the acrylic base with a laser etched 2×2 mm square and serial sections prepared for histological examination with PLM and TMR.

Fig. 2

A photograph of the PS-OCT systems showing the relative positions of the sample holder with tooth, scanning stages and probe. The incident beam is aligned with one corner of the brass holder so that the scan position can be matched to the position of serial sectioning for histology.

Fig. 3

Image series of PS-OCT (⊥-axis) (left), PLM (center), and TMR (right) for four different teeth, A–D. The lesion is demarcated by the black and gray boxes in the OCT and PLM images. OCT images are shown in a red-white-blue false color scale in dB with high reflectivity in red. The TMR false color scale is 16 color Rainbow representing mineral density with purple (high) to orange (low).

Fig. 4

Lesion depths measured using OCT, PLM and TMR for 20 teeth. Correlation plots are also shown for (OCT & PLM, solid line) r=0.63 (Pearson), P < 0.01 and (OCT & TMR – dotted line) r = 0.75, P < 0.001.