Inspect 50

Two central sticks were selected from each teeth of each subgroup (n = 10) and processed for nanoleakage assessment as previously described (Feitosa et al., 2012b) . In brief, bonded sticks were immersed in 50 wt% ammoniacal silver nitrate [Ag(NH 3 ) 2 ]NO 3 (aq) solution in total darkness for 24 h. Subsequently, the specimens were rinsed in H 2 O to remove the excess silver nitrate and then immersed in a photo-developing solution for 8 h under fluorescent light (60 cm from the specimens) to reduce silver ions into metallic silver grains along the resin-dentin interface. The silver-impregnated sticks were embedded in epoxy resin and wet-polished using #600, #1200, #2000 SiC papers and diamond pastes (Buehler) 3, 1, and 0.25 µm. The specimens were ultrasonically cleaned for 20 min after each abrasive/polishing step. Finally, they were air-dried, dehydrated for 48 h, coated with carbon and observed using a SEM (Inspect 50; FEI, Amsterdam, Netherlands) in backscattered electron mode for proper evaluation of silver impregnation along the interfaces.

Two resin-dentin sticks were selected from each bonded tooth and storage condition during the cutting procedure. These sticks were immersed in 50wt% ammoniacal silver nitrate (AgNO 3 (aq)) solution in complete darkness for 24h (16) . Subsequently, the specimens were rinsed with distilled water to remove the excess of silver nitrate and immersed in photo-developing solution for 8h under light to reduce silver ions into metallic silver grains. The silverimpregnated sticks were embedded in epoxy resin and polished using 600-, 1200-, 2000-grit SiC papers and diamond pastes (Buehler, Lake Bluff, IL, USA) with 1 and 0.25 µm particle sizes, and ultrasonically cleaned of 15min after each abrasive/polishing step. Specimens were finally air-dried, dehydrated overnight in silica gel under vacuum, coated with carbon and analyzed using SEM (Inspect 50, FEI, Amsterdam, Netherlands) and observed in backscattered electron mode at 20 kV.