A study on surface roughness and microleakage test in cavities prepared by Er:YAG laser irradiation and etched bur cavities.

The purposes of this study were to investigate the surface morphology, suface roughness of cavities prepared by Er:YAG laser irradiation, and compared the microleakage degree after composite resin restoration with etched bur cavities, in vitro. In each of the 30 human extracted teeth, two shallow cavities were prepared; one prepared with the Er:YAG laser system on the buccal surface, and one produced on the lingual (palatal) surface with a high-speed turbine. Five cavities from each group were investigated by scanning electron microscopy (SEM), and five were subjected to surface roughness analysis by a colour laser three-dimensional (3D) microscope. The remaining cavities were filled with a composite resin and subjected to a microleakage test under thermocycling. Only bur cavities were acid-etched before filling. Statistical analysis was performed using the Mann-Whitney U test; a value of p <0.01 was considered significant. Morphologically, the prepared cavities showed an irregular surface with the absence of a debris-like smear layer; enamel prisms and opening of dentinal tubules were recognised. Surface roughness was significantly increased with the laser system. Microleakage test revealed no significant differences between the laser and bur cavities. Crosscut sections of the cavities with no microleakage showed no gap at the interface. Laser cavity may facilitate good adaptation of composite resin with enamel and dentine, because an increase of surface roughness and the openings of dentinal tubules may facilitate the formation of a hybrid zone, since a primer and an adhesive can penetrate the surface better when the smear layer is removed. It can be concluded that shallow cavity prepared by Er:YAG laser is capable of decreasing microleakage of composite resin restorations, and its efficiency is similar to etched bur cavities.