Light and scanning electron microscopic observation of human dental occlusal enamel treated by pulsed Nd:YAG laser with fluoride

Abstract

The purpose of this study was to compare morphological changes of human occlusal enamel following pulsed Nd:YAG laser treatment with black ink, 38% Ag(NH 3) 2F or 2% NaF. Twenty-five extracted human teeth were randomly assigned to 5 groups: (1) non-treated group; (2) pulsed Nd:YAG laser treated only; (3) pulsed Nd:YAG laser irradiation after applying black ink; (4) pulsed Nd:YAG laser irradiation after applying 38% Ag(NH 3) 2F for 1 min; (5) pulsed Nd:YAG laser irradiation followed by applying 2% NaF for 4 min. The laser used in this study was pulsed Nd:YAG laser with pulse duration of 150 μs, pulse repetition of 20 pps, power of 2 W, and energy density was 48 J/cm 2. Specimens were observed by light and scanning electron microscope. Laser-induced enamel surface changes included melting and resolidification. Morphological changes of the specimens treated by laser after applying 38% Ag(NH 3) 2F for 1 min were similar to those of specimens lased after applying black ink except 1-2 μm diameter spheres on the former surface. The specimens of laser treatment followed by applying 2% NaF. for 4 min showed relatively smooth surfaces. By light microscope, the ground sections of each treatment group exhibited different depth of melted enamel. These results suggested that 38% Ag(NH 3) 2F could serve both as absorptive mediator and fluoride: applying 2% NaF for 4 min after laser irradiation could make the porous melted surface smoother.