The aim of this study was to investigate the sealing ability of different self-etch dental adhesives after different aging protocols. Sixty sound human third molars were used for this study. Two standardized Class II box cavities, with the gingival floor 1?mm below the cement-to-enamel junction were prepared in each tooth. Three adhesive groups (Clearfil SE Bond, Clearfil S3 Bond and Single Bond Universal) were subdivided into four subgroups (n?=?10) according to the aging protocols: 24?h water storage (control); 1-year water aging; 10,000 thermocycling; and 240,000 thermo-mechanical aging. After the aging protocols, a 50% silver nitrate solution was used as a tracer. The internal adaptation analysis was performed using a micro computed tomography system. All tested aging protocols increase the silver nitrate penetration compared with the controls (p??0.05). The amount of silver nitrate penetration increased after thermo-mechanical aging for all samples (p?