Ultramorphological SEM/TEM Analysis of the Resin-Dentin Bond Degradation: Nanoleakage Expression

Objectives: This study evaluated nanoleakage in bonded interfaces using two single-step self-etching adhesives (Adper Prompt, AD and One-up Bond F, OB), two two-step self-etching primers (Clearfil SE Bond, CF and Unifil Bond, UB), and a total-etch adhesive (Single Bond, SB). Methods: Flat dentin surfaces were bonded with the five adhesive systems and stored in water for 1 week or 6 months. After storage periods, teeth were sectioned into 0.9 mm thick slabs, coated with nail varnish except for the bonded interfaces, and immersed in ammoniacal AgNO₃ for 24 hours. After immersion in a photodeveloping solution for 8 h, specimens were observed under a scanning electron microscope (SEM) using the backscattered electron mode. Undemineralized, unstained, epoxy resin-embedded sections were prepared for transmission electron microscopy (TEM). Results: Nanoleakage patterns were observed in all bonded specimens. CF and UB presented the lowest nanoleakege patterns. UB showed a remarkable stability over the experiment, while CF presented increased nanoleakage after 6 months. SB presented accumulation of silver particles within the hybrid layer (HL), which was intensified after 6 months. AD and OB presented silver accumulation within the HL and in the adhesive as well, with an increased leakage pattern after 6 months for AD. Conclusions: The quality of the HL produced by the different bonding systems did not prevent nanoleakage at the bonding interface, which was remarkably increased after 6 months for the two-step self-etching CF, for the one-step AD, and for the total-etch SB. This study was supported by CAPES and FAPESP#01/13034-3