The nanoleakage phenomenon: influence of different dentin bonding agents, thermocycling and etching time

"Nanoleakage" takes place within the hybrid layer zone of the dentin-composite interface in spaces not occupied by polymerized resin. The purpose of this study was to quantify the amount of nanoleakage in specimens treated with one of six different bonding agents. For one agent, different etching times were used, and for two agents results after thermocycling were obtained. Standardized class V cavities were prepared in 165 extracted human molars with cervical margins located in dentin. After placement of the composite using bonding agents, the teeth were stored in a 1% rhodamin-B-isothiocyanate solution for 24 h at 20 degrees C, embedded in methacrylate, and sectioned parallel to the long axis of the tooth. A confocal laser scanning microscope was used to visualize a layer 10 microm below the prepared surface of the section. The lengths of the penetrated pathways were measured, representing the amount of nanoleakage. In all materials tested, penetration pathways appeared within the hybrid layer in absence of gap formation. Penetration lengths of the tested materials were in a range from 69 +/- 24 microm to 469 +/- 333 microm. Thermocycling had no statistically significant influence, and etching for 15 s resulted in statistically significantly shorter penetration compared to longer etching.