Influence of Tooth-surface Hydration on Optical Coherence Tomography Imaging

Objectives:

This study examined the influence of tooth-surface hydration conditions on optical coherence tomography (OCT) imaging. 

Methods:

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. 

Results:

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. 

Conclusions:

The current findings demonstrate that the hydration conditions of the tooth substrate must be taken into consideration during TD-OCT scanning.