Terahertz time-domain spectroscopy for monitoring the curing of dental composites

Abstract

We apply terahertz (THz) time-domain spectroscopy for monitoring the curing process of three different light-curing dental composites. Exact knowledge of the sample thickness is required for a precise determination of the THz dielectric parameters, as the materials exhibit shrinkage when they are cured. We find very small but significant changes of the THz refractive index and absorption coefficient during stepwise light exposure. The changes in the refractive index are correlated with changes in the density of the materials. Furthermore, the refractive index and the sample thickness are found to give the most reliable result for monitoring the curing process of the dental composites.

Functional THz emitters based on Pancharatnam-Berry phase nonlinear metasurfaces

“…Furthermore, their penetration into optically opaque materials can be applied to remote inspection of concealed areas for security 6 or inspecting circuits in electronic devices 7 , and even studying hidden layers in paintings 8 . Moreover, they can also be used as non-invasive and non-ionizing radiation sources for early detection of numerous medical conditions, such as skin cancer 9 and cavities in teeth 10 . In addition, the use of circularly polarized light sources across various regions of the electromagnetic spectrum, as well as the THz frequency band, has attracted interest for applications of circular dichrosim spectroscopy 11 .…”

THz in vivo measurements: the effects of pressure on skin reflectivity

“…Terahertz (THz) radiation (0.1 THz to 10 THz) is currently attracting a lot of interest in biomedical research [1][2][3]. Based on its unique properties, such as non-invasiveness and high sensitivity to water, it has the potential to be used for in vivo medical imaging and diagnosis.…”

Assessment of curing behavior of light‐activated dental composites using intensity correlation based multiple reference optical coherence tomography

“…However, speckle imaging techniques are limited by their superficial imaging capability and cannot provide depth‐resolved information about the curing process. Terahertz (THz) time‐domain spectroscopy has recently been applied to monitor the curing of dental composites by measuring the THz refractive index and absorption coefficient . However, this technique requires exact knowledge of the sample thickness for determining the precise dielectric parameters.…”