In TPI, at each position within a scan the entire terahertz waveform is acquired which contains depth information. From this information the time of flight and absorption information can be extracted. Images can be constructed to show cross sections of the sample in three different orthogonal orientations, and also 3-dimensional reconstructions.
METHOD: In a pilot study we have used terahertz technology to study a number of in vitro samples of various individual restorative filling materials including glass ionomers, composites, temporary dressings and amalgam. We have also scanned extracted teeth containing dental restorations in order to image the tooth-filling interface. Through software analysis, we evaluated the terahertz waveform in different formats (time domain, frequency domain) to find the most meaningful way of interpreting the data.
RESULTS: The terahertz images show good contrast between different types of restorative filling materials and between these filling materials and the tooth interface.
CONCLUSION: Terahertz imaging is potentially useful to distinguish different restorative filling materials and to demonstrate the interface between these materials and the tooth surface.