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: Five 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 mu m. Laser fluorescence readings were taken along the same line and at the same sites using a DIAGNOdent pen. Results: H, E, and LF readings from cervical enamel were within the expected range for normal sound enamel. After log transformation of the H and E measurements to allow for linear correlation analysis, there was a significant and moderately strong inverse correlation between LF and H or E samples (r (between specimens) = 0.59, r (between specimens) = 0.39, respectively; p < 0.001). Conclusions: This study shows that, in the absence of dental caries, 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. (C) 2008 Elsevier Ltd. All rights reserved.