Imaging carious dental tissues with multiphoton fluorescence lifetime imaging microscopy

In this study, multiphoton excitation was utilized to image normal and carious dental tissues noninvasively. Unique structures in dental tissues were identified using the available multimodality (second harmonic, autofluorescence, and fluorescence lifetime analysis) without labeling. The collagen in dentin exhibits a strong second harmonic response. Both dentin and enamel emit strong autofluorescence that reveals in detail morphological features (such as dentinal tubules and enamel rods) and, despite their very similar spectral profiles, can be differentiated by lifetime analysis. Specifically, the carious dental tissue exhibits a greatly reduced autofluorescence lifetime, which result is consistent with the degree of demineralization, determined by micro-computed tomography. Our findings suggest that two-photon excited fluorescence lifetime imaging may be a promising tool for diagnosing and monitoring dental caries

Fluorescence in Dissolved Fractions of Human Enamel

Fluorescence induced by laser light is useful in early detection of enamel caries. The present work studied the fluorescence emission pattern in dissolved human enamel and in different molecular weight fractions obtained after gel chromatography or dialysis followed by ultrafiltration. For comparison, solutions of synthetic hydroxyapatite and bovine enamel were used. When the entire emission and excitation spectra of the corresponding excitation and emission wavelengths in the solutions of human enamel and bovine enamel were compared, no distinct differences were found between the solutions. With excitation at 375 nm, emission peaks were found at 460 and 560 nm, indicating the presence in human enamel solution of two different chromophores, unevenly distributed over the molecular weight fractions. The 460-nm and the lower 560-nm fluorescence peaks seem to be derived from both organic and inorganic components. The inorganic substances contributing to both the 460-nm and 560-nm peaks were incorporated in complexes. The 560-nm emission peak elucidates part of the basis of the laser fluorescence method

Fluorescence of natural teeth and restorative materials, methods for analysis and quantification: A literature review

Objective: This review integrates published scientific information about the fluorescence of natural teeth, dental resins and ceramics, and the main methods of analysis and quantification presented in the literature. Overview: Fluorescence is an emission of light (photons) by a substance that has absorbed light of higher energy. In natural teeth, it is more intense in the dentin than in the enamel and presents a bluish-white color. In dental resins and ceramics, fluorescence is obtained by the incorporation of materials that contain rare-earth luminescence centers (more precisely lanthanide luminescence centers), which allows these artificial materials to simulate natural teeth in a more beautiful and vital-looking way. However, the lack of knowledge about this optical phenomenon on the part of professionals indicates the need for more scientific studies and dissemination on this topic. Conclusions: Aesthetic materials have variable spectral compositions and fluorescence intensities, which are not always compatible with natural teeth. The fluorescence of teeth and restorative materials can be influenced by several factors, such as aging, temperature, and bleaching. Several devices for fluorescence evaluation and quantification are used in studies under different methodologies, but the small number of studies on the subject make it difficult to compare their results. Clinical Significance: Fluorescence is a fundamental optical property for aesthetic rehabilitations since its presence and intensity in the restorative materials allows achieving an aesthetic result much closer to reality. However, the fluorescent behavior of natural teeth and aesthetic restorative materials is not yet fully understood by researchers and clinicians. Greater understanding of this phenomenon will contribute to the selection, indication, and clinical use of these materials.CAPES (Coordination for the Improvement of Higher Education Personnel), Brazil, Grant/Award Number: 88881.119044/2016-01 and FCT (Foundation for Science and Technology), Portugal, Grant/Award Number: NORTE 01-0145-FEDER-000018, POCI-01-0145-FEDER-006941, UID/EEA/04436/2013