Morphological and Chemical Changes of Deciduous Enamel Produced by Er:YAG Laser, Fluoride, and Combined Treatment

Objective: The purpose of this study was to evaluate in vitro morphological and chemical changes on human deciduous enamel produced by Er:YAG laser irradiation, fluoride application, combined treatment, and acid dissolution. Background data: Er: YAG laser has been proposed as a potential preventive dental caries strategy. There is scarce information regarding deciduous enamel. Methods: Eighty enamel samples were assigned to eight groups (n = 10): G1, control; G2, G3, and G4, Er: YAG laser irradiation at 7.5, 12.7, and 39.8 J/cm(2), respectively; G5, fluoride application; G6, G7, and G8, irradiation at previous densities plus fluoride application. Morphology was evaluated by scanning electron microscopy, and chemical composition was determined by energy dispersive X-ray spectroscopy before treatment (BT), after treatment (AT), and after acid dissolution (AAD). One way and repeated measures analysis of variance (ANOVA) were used (p <= 0.05). Results: Morphology of lased surfaces included craters, exposed prisms, fractures, and melting. No morphological modifications appeared after fluoride application, or AAD. Chemically, AT: C atomic percentage (at%) decreased in G3, G4, and G8; O at% decreased in G5-G8; F content was higher for G7; trace elements remained under 1.0 at%; Ca at % increased in G4, G7, and G8; there were increments in P at% in G4 and G8; and Ca/P increased in G4, G7, and G8. AAD: F at% dropped to 0.00 in G5-G8; and P at% increased in G7. Conclusions: Morphological changes of Er: YAG irradiated enamel represented mild to severe damages. Conditions employed in this study are not recommended for deciduous caries prevention. Er: YAG energy density influenced chemical changes in enamel to enhance its structure. Acid dissolution removed fluoride from enamel surface.