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Dental caries remain one of the most common oral diseases in the world. Current detection methods, such as dental
explorer and X-ray radiography, suffer from poor sensitivity and specificity at the earliest (and reversible) stages of the
disease because of the small size (< 100 microns) of early-stage lesions. We have developed a fine-resolution (480 nm),
ultra-broadband (1 GHz), all-optical photoacoustic imaging (AOPAI) system to image and detect early stages of tooth
decay. This AOPAI system provides a non-contact, non-invasive and non-ionizing means of detecting early-stage dental
caries. Ex-vivo teeth exhibiting early-stage, white-spot lesions were imaged using AOPAI. Experimental scans targeted
each early-stage lesion and a reference healthy enamel region. Photoacoustic (PA) signals were generated in the tooth
using a 532-nm pulsed laser and the light-induced broadband ultrasound signal was detected at the surface of the tooth
with an optical path-stabilized Michelson interferometer operating at 532 nm. The measured time-domain signal was
spatially resolved and back-projected to form 2D and 3D maps of the lesion using k-wave reconstruction methods.
Experimental data collected from areas of healthy and diseased enamel indicate that the lesion generated a larger PA
response compared to healthy enamel. The PA-signal amplitude alone was able to detect a lesion on the surface of the
tooth. However, time- reversal reconstructions of the PA scans also quantitatively depicted the depth of the lesion. 3D
PA reconstruction of the diseased tooth indicated a sub-surface lesion at a depth of 0.6 mm, in addition to the surface
lesion. These results suggest that our AOPAI system is well suited for rapid clinical assessment of early-stage dental
caries. An overview of the AOPAI system, fine-resolution PA and histology results of diseased and healthy teeth will be
presented.
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