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

"Nanoleakage" takes place within the hybrid layer zone of the dentin-compos ite interface in spaces not occupied by polymerized resin. The purpose of t his study was to quantify the amount of nanoleakage in specimens treated wi th one of six different bonding agents. For one agent, different etching ti mes 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-isothiocyana te solution for 24 h at 20 degrees C, embedded in methacrylate, and section ed parallel to the long axis of the tooth. A confocal laser scanning micros cope was used to visualize a layer 10 mu m below the prepared surface of th e section. The lengths of the penetrated pathways were measured, representi ng 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 mu m to 469 +/- 333 mu m. Thermocycling had no statistically significant influence, and etching for 15 s resulted in statistically significantly shorter penetrati on compared to longer etching.