The effect of NaOCl dentin treatment on nanoleakage formation

The term "nanoleakage" has been introduced to explain a penetration pathway within hybrid layers of the dentin-composite junction in the absence of gap formation. This phenomenon is argued in the literature to be a risk factor for the quality of the dentin bonding. NaOCl is a well-known agent used to remove collagen layers that are exposed after acid etching. The purpose of this study was to determine the influence of an NaOCl treatment of dentin to the formation of nanoleakage. Class V cavities were prepared in 40 human molars with the cervical margins located in dentin. After etching with phosphoric acid, 20 samples were treated with 10% NaOCl for 60 s, and 20 samples were used as control. Composite restorations were placed using two different bonding systems. The specimen were exposed in silver nitrate solution and then in developer. After embedding, the teeth were sectioned, dried, coated with gold, and analyzed by SEM. For all the specimen in the control group, backscatter images indicated a silver penetration within the hybrid layer. There was no penetration of silver detectable in the teeth that were treated with NaOCl. We conclude that the removal of the collagen layer by using NaOCl avoids the formation of nanoleakages with the materials tested.