Influence of tooth-surface hydration conditions on optical coherence-tomography imaging

Abstract

ObjectivesThis study examined the influence of tooth-surface hydration conditions on optical coherence tomography (OCT) imaging. MethodsEmitted 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 1kHz. Backscattered light from the sample was coupled back to the system, digitised 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 10s (‘air-blow’ condition), and at intervals thereafter (‘1-min’, ‘5-min’ and ‘10-min’ conditions, respectively). ResultsFor the wet condition, three distinct peaks indicated the water surface, tooth surface and dentino-enamel junction. Backscattered light was detected at levels above noise, possibly causing grainy OCT images. By contrast, two distinct peaks indicating the tooth surface and dentino-enamel junction were observed for the air-blow and 10-min conditions, with greater signal intensities for the latter. The intensity was lower for the air-blow condition than the wet condition. The signal intensities decreased during storage in air at room temperature. ConclusionTooth-substrate hydration conditions thus appeared to influence time domain-OCT imaging.