Detection of interproximal demineralized lesions on human teeth in vitro using frequency-domain infrared photothermal radiometry and modulated luminescence

Abstract

Frequency-domain photothermal radiometry (FD-PTR or PTR) is used to detect mechanical holes and demineralized enamel in the interproximal contact area of extracted human teeth. Thirty-four teeth are used in a series of experiments. Preliminary tests to detect mechanical holes created by dental burs and 37% phosphoric acid etching for 20 s on the interproximal contact points show distinct differences in the signal. Interproximal contact areas are demineralized by using a partially saturated acidic buffer system. Each sample pair is examined with PTR before and after micromachining or treating at sequential treatment periods spanning 6 h to 30 days. Dental bitewing radiographs showed no sign of demineralized lesion even for samples treated for 30 days. Microcomputer tomography (micro-CT), transverse microradiography (TMR), and scanning electron microscopy (SEM) analyses are performed. Although micro-CT and TMR measured mineral losses and lesion depths, only SEM surface images showed visible signs of treatment because of the minimal extent of the demineralization. However, the PTR amplitude increased by more than 300% after 80 h of treatment. Therefore, PTR is shown to have sufficient contrast for the detection of very early interproximal demineralized lesions. The technique further exhibits excellent signal reproducibility and consistent signal changes in the presence of interproximal demineralized lesions, attributes that could lead to PTR as a reliable probe to detect early interproximal demineralization lesions. Modulated luminescence is also measured simultaneously, but it shows a lower ability than PTR to detect these interproximal demineralized lesions.

Alternative methods to visual and radiographic examinations for approximal caries detection

“…For early approximal caries detection, PTR has shown an increase in the amplitude by more than 300% after 80 h of artificial demineralization. However, LUM was found to have a lower ability than PTR to detect early approximal lesions (77,78). An in vitro study evaluated the performance of PTR/LUM, visual examination, and radiography, with polarized light microscopy as a gold standard for approximal caries detection.…”

“…The PTR/LUM caries detection method has demonstrated higher Sn and Sp than visual examination, radiography, and LF for early occlusal caries detection (77). For early approximal caries detection, PTR has shown an increase in the amplitude by more than 300% after 80 h of artificial demineralization.…”

Diagnostic Imaging and Spectroscopy

“…In theory, the depth of those structures can be calculated by analyzing the temporal profile of the thermal emission from the sample. The incident thermal radiation can be temporally modulated for frequency-domain photothermal radiometry (FD-PTR) and Mandelis and co-workers [118][119][120][121] have applied FD-PTR to detect and analyze dental caries, cracks, and other subsurface structures in teeth. Analysis of the phase and amplitude of the PTR signals at different modulation frequencies provides depth-specific information.…”

“…(b) PTR and LUM phase and amplitude measurements at 5 Hz across the proximal contact point before and after drilling holes in each tooth. From reference[118].…”

Early Enamel Lesion: Part I. – Classification and Detection

“…Frequencydomain photothermal radiometry (FD-PTR or PTR) and modulated luminescence have also been used to detect early interproximal demineralized lesions. However PTR provides more accurate diagnosis than modulated luminescence (48). Laser fluorescence device DIAGNOdent has been used to detect occlusal caries and has more sensitivity and specificity than radiographic examination (2).…”