Evaluation of Four Different Adhesive Systems’ Bonding Strength Between Superficial and Deep Dentin

The success of adhesive restorations largely depends on the optimal bond strength between the tooth structure and the restorative material. The aim of this study was to evaluate the shear bond strength (SBS) of four different adhesives applied to mandibular molars on deep and superficial dentin. The total of 56 teeth used in the study were randomly divided into 2 subgroups of superficial dentin and deep dentin participants (n = 28). Superficial and deep dentin groups were randomly divided into 4 subgroups (n = 7) for application with different adhesive agents. We formed the following groups: Group 1 (G1)—deep dentin and GC bonding agent (G-Premio BOND); Group 2 (G2)—superficial dentin and GC bonding agent; Group 3 (G3)—deep dentin and Clearfil S3 bond bonding agent (Clearfil TM S3 BOND); Group 4 (G4)—superficial dentin and Clearfil S3 bond bonding agent; Group 5 (G5)—deep dentin and KerrOptibond bonding agent (KerrOptibondTM Universal); Group 6 (G6)—superficial dentin and Kerr Optibond bonding agent; Group 7 (G7)—deep dentin and 3M-ESPE universal bonding agent (3M ESPE); Group 8 (G8)—superficial dentin and 3M-ESPE universal bonding agent. The silicone block with a diameter of 3 mm and a thickness of 1 mm was placed in the middle of the occlusal surface and the test composite was loaded. All prepared specimens were aged in thermal cycles at 5–55 °C for 5000 cycles. The teeth were subjected to SBS (shear bond strength) tests at a crosshead speed of 1 mm/min in a universal testing machine. In all adhesive systems, deep dentin showed a higher bond strength than superficial dentin and the bond strength value was statistically significant (p = 0.05). The bond strength in all tested adhesive systems was observed to be significantly higher in deep dentin than in superficial dentin.