This study examined the influence of tooth-surface hydration conditions on optical coherence tomography (OCT) imaging.
Emitted light was coupled in a single-mode fibre-optic Michelson interferometer, and delivered to a sample and a reference mirror mounted on a linearly translating galvanometer driven by a triangular voltage waveform at a fringe-modulation frequency of 1 kHz. Backscattered light from the sample was coupled back to the system, digitized and used to create two-dimensional images together with beam scanning. OCT imaging of the occlusal surfaces of 10 extracted human teeth was performed soon after mounting (‘wet’ condition), immediately after air blowing for 10 s (‘air-blow’ condition), and at intervals thereafter (‘1-min’, ‘5-min’ and ‘10-min’ conditions, respectively). The data for each group were subjected to the Tukey-Kramer test at a significance level of 0.05.
The mean signal intensities for enamel surfaces under different surface-moisture conditions are listed below.
Condition Wet Air blow 1 min 5 min 10 min
Intensity (dB) –79.5 (1.8) a –64.6 (4.6) b –62.9 (4.6) b –53.0 (3.8) c –44.1 (1.8) d
n = 5, values in parenthesis indicate standard deviations.
The signal intensities were calculated from a series of line profile integrations in the perpendicular axis (A-scan) over the enamel surface area. The intensity was significantly lower for the air-blow condition than the wet condition. The signal intensities decreased over time when the tooth substrates were stored in air at room temperature.
The current findings demonstrate that the hydration conditions of the tooth substrate must be taken into consideration during TD-OCT scanning.
Keywords: Caries, Diagnosis, Digital image analysis and OCT
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