Chen, S.-Y.S.-Y.ChenHsu, C.-Y.S.C.-Y.S.HsuCHI-KUANG SUN2018-09-102018-09-10200810944087http://www.scopus.com/inward/record.url?eid=2-s2.0-47849111035&partnerID=MN8TOARShttp://scholars.lib.ntu.edu.tw/handle/123456789/340718https://www.scopus.com/inward/record.uri?eid=2-s2.0-47849111035&partnerID=40&md5=c5c027aa7335039bc1b8a5127ada2dafEnamel covers the tooth crown and is responsible for protecting the inner tissues of the teeth. It is thus clinically important to diagnose the anomalies in tooth enamel structures in the early stage for prevention and treatment. In this article, we report the epi-harmonic-generationmicroscopic study of various abnormal enamel from the nature surface of human teeth. With a 1230 nm light source and with an epi-collection scheme, an imaging depth greater than 300μm can be achieved. The contrast sources of THG and SHG in the abnormal enamel have been identified and verified by comparing the images from the sound enamel with those from white spot lesions, cracks, and the irradiated enamel. Besides the previously reported interprismatic space, THG is found to be contributed from cracks or the material inhomogeneities inside the enamel prisms; while SHG is attributed to the strain-induced breakage of the 6/m point group symmetry. Combined with the high 3D spatial resolution and no energy release during imaging, our study shows that the infrared-laser-based epi-harmonic generation microscopy can provide different contrasts to differentiate the abnormal enamel from sound enamel and could provide a valuable tool for in vivo monitoring of both morphological changes and strain status of hydroxyapatite crystals in the enamel without sectioning and staining. ©2008 Optical Society of America.[SDGs]SDG3Cracks; Enamels; Harmonic analysis; Light sources; Nonlinear optics; Tooth enamel; Collection schemes; Harmonic generation microscopy; Hydroxyapatite crystals; Material inhomogeneities; Microscopic imaging; Morphological changes; Point group symmetry; Spatial resolution; Harmonic generation; article; computer assisted diagnosis; enamel; equipment; equipment design; human; instrumentation; methodology; microscopy; pathology; tooth disease; Dental Enamel; Equipment Design; Equipment Failure Analysis; Humans; Image Interpretation, Computer-Assisted; Microscopy; Tooth Diseasesjournal article186484882-s2.0-47849111035