Quantitative imaging of fluorine in human teeth by cryogenic laser ionization time-of-flight mass spectrometry

The scarcity of techniques for visualizing fluorine (F) hinders the comprehensive understanding of the role of anti-caries fluorides. This study introduced a liquid nitrogen cooling device into the laser ionization source to construct a novel cryogenic laser ionization time-of-flight mass spectrometry (Cryo-LI-TOFMS) imaging platform for F. The technique eliminated the interference of water-related species at m/z 19 and realized F imaging with a spatial resolution of 20 mu m. The quantitative imaging of 9 major elements in human teeth, including F, confirmed the feasibility of this method and revealed teeth compositions and mineralization environment. The quantitative imaging of F in teeth treated with different topical anti-caries drugs or different application times clarified the site and time of drug action, providing a solid foundation and promising prospects for drug research.