Optical Coherence Tomography for dental caries detection and analysis

The ability of an en-face Optical Coherence Tomography (OCT) system to detect and quantitatively monitor the demineralisation of teeth to produce enamel and dentine (root) caries was determined and validated with an established method of quantifying demineralisation, transverse microradiography (TMR). We used an OCT system which can collect A-scans, B-scans (longitudinal images) and C-scans (en-face images). The development of enamel and root caries, by 3-day demineralisation in acidic buffer solution, was assessed quantitatively every 24 hours. Caries lesions were shown as volumes of reduced reflectivity in both the transversal and longitudinal images. The A-scan, which showed the levels of reflectivity versus the depth of penetration into the tissue, was used for the quantitative analysis of the lesions. Results demonstrated that the reflectivity of tooth tissue decreased with increasing demineralisation time. A linear correlation was observed between the mineral loss in enamel (r=1.0) and dentine (r = 0.957) measured by TMR and the percentage reflectivity loss measured by OCT. We concluded that OCT could detect incipient enamel and root caries and quantitatively monitor the demineralisation of the tissue. The reflectivity loss in tooth tissue during demineralisation, measured by OCT, could be related to the amount of mineral lost during the demineralisation.