Background and aim; Bulk fill resin composites have been proven in several studies to enable restoration in thick layers, up to 4mm, maintaining the mechanical properties and the degree of conversion within the whole increment. This study was designed to evaluate micro tensile bond strength (µTBS) of bulk-fill composite resins to superficial and deep dentin with different adhesion approaches.
Materials and methods; Extracted human premolar teeth (n=24) were used to prepare 120 resin-dentin sticks. Specimens were divided into two main groups according to the type of bulk –fill composite used (Xtra fill & Tetric-N- Ceram). Each main group was subdivided according to the adhesive approach used into (total & self-etch). According to dentin depths each subgroup was further categorized into (superficial and deep). µTBS was evaluated using universal testing machine at a crosshead speed of 0.5 mm/min. Dentin / resin interfaces were assessed by scanning electron microscopy.
Results; The results showed significant (p<0.05) effect of composite and dentin level on µTBS, while the effect of adhesive approach was non-significant (p>0.05).
Conclusion; Xtra-Fill has higher µTBS than Tetric Bulk- fill. Total- etch adhesive system has higher µTBS than self-etch with the superficial dentin. Self-etch adhesive system has higher µTBS than total etch with the deep dentin.