Use of SWIR dehydration and OCT to assess the complete arrest of simulated incipient caries lesions.

Previous studies have shown that optical coherence tomography (OCT) can be used to show the formation of a transparent surface zone on caries lesions indicative of remineralization. Studies have also shown that monitoring changes in the diffuse reflectivity of caries lesions during drying with air can be used to assess lesion activity and that the largest changes occur at SWIR wavelengths coincident with high water absorption at 1450 and 1950 nm. The purpose of this study was to determine when remineralization has occurred by monitoring changes in SWIR reflectance measurements and OCT images of simulated lesions over an extended time period during exposure to a remineralization solution. Eight bovine enamel surfaces each with two treatment windows were exposed to a pH cycling regimen to produce simulated lesions 50-100 μm deep. OCT at 1310 nm was used to image the samples at each time point. An extended range tungsten halogen lamp with a 1450 nm band pass filter and a broadband amplified spontaneous emission source centered near the peak of the water-absorption band at 1950 nm were used as light sources. An extended range InGaAs camera (1000-2340 nm) was used to acquire reflected light images as the samples were dried with air. After 32 days of exposure to the remineralization solution there were no further changes to the samples suggesting they had been completely arrested.