Thermophotonic Detection of Demineralized Root and Enamel Lesions

Objectives: The potential of frequency-domain photothermal radiometry (FD-PTR, PTR) and modulated luminescence (FD-LUM, LUM) to detect artificially created demineralized and remineralized lesions on the root and enamel of human teeth has been assessed.

Methods: Fourteen extracted human teeth were used and mounted on LEGO bricks for precise remounting. The sample was controlled by precision micro-stages and data were acquired by a computer to avoid operator bias. The experimental setup consisted of a semiconductor laser (659 nm, 120mW), a mercury-cadmium-telluride IR detector for PTR, a photodiode for LUM, two lock-in-amplifiers, and a computer. A lesion was created on a 1mm x 4mm rectangular window, spanning root to enamel surface, using an acidified gel to demineralize the tooth surface. The samples were subsequently immersed in a remineralization solution. Each sample was examined with PTR/LUM on root and enamel before and after treatment at times from 1 to 10 days of demineralization and 2 to 10 days of remineralization for only the 10-day-demineralized samples. After completing all the experiments, TMR and micro-CT analyses were performed to correlate the PTR/LUM signals to depth of lesions and mineral losses.

Results: PTR/LUM signals showed gradual and consistent changes with treatment time. In this study, TMR showed good correlation coefficients (0.6-0.8) with PTR/LUM, while micro-CT showed poor correlation.

Conclusions: PTR/LUM is able to detect and monitor demineralization and remineralization on root and enamel surfaces of human teeth. It was also found that treatment time duration did not correlate well to any technique, PTR/LUM, TMR or micro-CT which is indicative of significant variations in demin/remin rates among different teeth as well as across the individual teeth.