Third-harmonic generation microscopy reveals dental anatomy in ancient fossils

Abstract

Fossil teeth are primary tools in the study of vertebrate evolution, but standard imaging modalities have not been capable of providing high-quality images in dentin, the main component of teeth, owing to small refractive index differences in the fossilized dentin. Our first attempt to use third-harmonic generation (THG) microscopy in fossil teeth has yielded significant submicrometer level anatomy, with an unexpectedly strong signal contrasting fossilized tubules from the surrounding dentin. Comparison between fossilized and extant teeth of crocodilians reveals a consistent evolutionary signature through time, indicating the great significance of THG microscopy in the evolutionary studies of dental anatomy in fossil teeth.

Third harmonic generation microscopy of cells and tissue organization

“…Owing to its noninvasive nature, THG allows 3D reconstructions and morphometric analyses of dentinal structures without the need for histological preparation. These proof-of-concept results suggest that THG could contribute to classify the evolution of ancient vertebrate teeth without damaging rare fossils (Chen et al, 2015).…”

Linear and nonlinear optical effects in biophotonic structures using classical and nonclassical light

“…The comparison between the dental anatomy of fossilized and currently living crocodilians provided with new insights in these species' evolution. The evolutionary signature of crocodilian teeth was found to be consistent over time .…”

Label-Free Fried Starchy Matrix: Investigation by Harmonic Generation Microscopy

“…THG was also explored for mapping optical heterogeneities in biological samples [29,30]. THG occurs at structural interfaces, such as local transitions of the refractive index whereby the combined energy of three photons is converted into one emitted photon with one third of the excitation wavelength and tripled energy [31].…”