Relationship Between Laser Fluorescence and Enamel Hypomineralisation

Objectives: to study the relation between the mechanical properties of hypomineralised enamel, and its laser fluorescence (LF). Methods: 5 extracted teeth with molar-incisor-hypomineralisation (MIH) were sectioned longitudinally through the defects and polished to prepare the hypomineralised enamel for testing. Hardness (H) and elastic modulus (E) of enamel were measured using nanoindentation. Measurement recording started from the cervicoenamel junction and proceeded occlusally in increments of 200 µm. Laser fluorescence readings were taken along the same line and at the same sites using DIAGNOdent pen. Results: H, E, and LF readings from cervical enamel were within the expected range for normal sound enamel. There was a significant and moderately strong inverse correlation between LF and H or E (R = 0.69, R = 0.64, respectively; p < 0.001). The correlation curve was curvilinear. Conclusion: This study shows that increased DIAGNOdent readings can indicate enamel hypomineralisation. While the increased LF readings in carious enamel are thought to be related to the presence of caries bacterial metabolites, the increased readings in hypomineralised enamel may be related to proteins in the hypomineralised enamel, and/or light scattering by the inhomogeneous enamel.