Effect of composite resin placement and use of an unfilled resin on the microleakage of two dentin bonding agents.

The purpose of this study was to assess, in vitro, the microleakage of Class V restorations using two third generations dentin bonding agents, with a hybrid light polymerized composite resin. One of the bonding agents was of the NPG-PMDM type and the other was a polyhexanide. Restorations were placed in cavities prepared in extracted human premolars using either a bulk or incremental packing technique. The NPG-PMDM-based agent was used with and without an intermediary unfilled resin. The teeth were stored for 1 week at 37 degrees C, thermocycled for 1500 cycles between 55 degrees C, 37 degrees C and 5 degrees C and the restorations examined for leakage using methylene blue dye. The teeth were sectioned through the restorations and the degree of microleakage assessed visually. All groups of restorations showed some degree of leakage at the gingival margin. Statistical analysis showed that there were significant differences in the amounts of leakage (P less than 0.001). There was no difference in leakage between any of the groups that had been restored using the NPG-PMDM system (P greater than 0.05). There was, however, less leakage of the incrementally filled group compared with the bulk-packed group with the polyhexanide agent (P less than 0.05). When the two bonding agents were compared, there was no significant difference in leakage (P greater than 0.05) except for the incrementally-packed polyhexanide and the incrementally-packed NPG-PMDM with unfilled resin (P less than 0.05). Only one specimen in any of the groups leaked at the enamel margin.