The effects of pulsed Nd:YAG laser irradiation with fluoride on root surface

This study evaluated the effects of pulsed Nd:YAG laser treatment on root surface in vitro with or without fluoride. Fifty specimens of human teeth were randomly assigned to five different treatment groups: (1) untreated group; (2) laser-treated only; (3) laser-treated after applying black ink; (4) laser-treated after applying 38% Ag(NH3)2F for 1 min; (5) laser-treated followed by applying 2% NaF for 4 min. Following their respective treatments, all specimens were prepared for evaluation by light microscopy, scanning electron microscopy, and EDX (Energy dispersive x-ray spectroscopy). Specimens from group 2 to 4 exhibited gross alterations of root surface not observed in controls such as pitting, crater formation, cracking, and porous globules. The specimens of group 5 had rough surfaces with some particles of approximately 1-micron diameter on the root surface. The fluoride uptake into the root measured by EDX was higher in groups 4 and 5. The depth of penetration of fluoride and silver was approximately 20 microns. Under light microscopy, the specimens of group 2, 3, 4, and 5 revealed some melted cementum, with no changes of underlying dentin. The results of this in vitro study suggested that the laser irradiation with or without fluoride, altered the morphology of the root surface and improved the fluoride uptake into the root surface. Whether the laser-induced surface changes with or without fluoride are beneficial to prevention of root surface caries needs to be studied further.