Objective: This in vitro study aimed to assess the microleakage at the tooth-adhesive interface underneath metal-brackets, either bonded with a conventional or a nano-adhesive system.
Materials and Methods: Dye penetration method was used to evaluate microleakage at the enamel-bracket interface. Twenty freshly-extracted human maxillary and mandibular premolars (average age: 15.47 ± 2.18 years) were randomly divided into two groups (n = 10/group/type of bonding composite). Group 1: metal-brackets bonded with conventional light-cured Transbond XT (3M-Unitek); Group 2: metal-brackets bonded with the light-cured flowable nano-hybrid composite Grandio SO Flow (Voco-Germany) used in combination with a one-step self-etch dual-cured adhesive, Futurabond DC (Voco-Germany). Specimens were thermocycled, immersed in Fuchsin dye, sectioned longitudinally, and evaluated for microleakage. Microleakage was recorded at the adhesive-enamel interface on both occlusal and gingival margins. Statistical analysis was performed using t-test as well as the paired t-tests.
Results: Both groups demonstrated microleakage at the adhesive-enamel interface, yet the metal-brackets bonded with the nano-composite Grandio SO Flow (G2) exhibited significantly higher microleakage values at the adhesive-enamel interface compared to brackets bonded with the conventional composite material (p < 0.05).
Conclusions: Flowable nano-composites may still not be the adhesive of choice for bracket bonding due to their remarkable microleakage at the enamel-adhesive interface in comparison to conventional light-cured Transbond XT (3M-Unitek).