Scanning electron microscopic study of laser-induced morphologic changes of a coated enamel surface.

A low-energy Nd:YAG laser was used to irradiate extracted human teeth coated with a black energy-absorbent laser initiator in a study to determine the extent of the morphologic changes produced in the enamel surface. The laser initiator was applied to a cleaned enamel surface and irradiated at an energy output of 30 mJ or 75 mJ. Both energy levels produced morphologic changes of the surface. There was a sharp line of demarcation between the coated, irradiated area and the surrounding noncoated enamel surface. The scanning electron microscope view at the lower energy level showed that the surface had melted and reformed with numerous small, bubble-like inclusions. The 75 mJ energy level showed individual impact craters with shallow centers and raised edges containing numerous pores and large, bubble-like inclusions. Etching is a dental procedure in which an acid is normally used to remove a thin outer layer of the tooth structure. This is necessary to create a roughened, irregular surface in order to provide mechanical retention for dental restorative materials. The changes produced by the laser in this study suggest a simple, effective, and controlled method of etching the enamel surface of a tooth by altering its surface characteristics.