Abstract:

Objective　To investigate the effect of pulse Nd:YAG laser combined with NaF on caries resistance of human enamelin vitro.Methods　24 caries-free, constant premolares were cut into enamel mass. Surface ultrastructure and fluoride distribution of enamel in laser-NaFtreated group, lasertreated group, NaFtreated group and control groupwere observed by scan- ning electron microscope (SEM) and electron probe microanalyzer.Results　①SEMobservation: In laser-NaFtreated group, the smear layer was almost removed, the enamel surface showed partially melted-like and bubble-like appearance, diffuse white-small particles distributed on enamel surface, and melted position, microcrack and microhole appeared whitely blocking-reflection. ②Electron probe microanalyzer analysis: In enamel samples, the highest average Ci of F-and the hightest depth which F-en- tered in enamel were recorded in the laser-NaF treated group. The average Ci of F-in laser-NaF treated group was significantly increased compared with that in NaF-treated group or laser-treated group or control group (P<0·001).Conclusion　The pulsed Nd:YAG laser combined with sodium fluoride could make the enamel surface partially melt, change the structure of the crystal, enhance the absorption of fluoride, and clear smear layer. This technology may resist the caries.

Key words: pulsed Nd:YAG laser, sodium fluoride, enamel, scanning electron microscope, electron probe microana- lyzer