Evaluation of fracture resistance of premolars restored with packable composite resin using different types of adhesive systems

Purpose The aim of this study was to evaluate the fracture resistance of human extracted premolars restored with packable composite resin by using three types of adhesive systems: two‑step etch‑and‑rinse system, two‑step self‑etch primer adhesive system, and one‑step self‑etch adhesive system. Materials and methods Fifty sound maxillary second premolars were selected. Forty specimens received class II mesio‑occluso‑distal cavities with a 2 ± 0.2 mm pulpal depth, 1.5 ± 0.2 mm gingival width, 2 ± 0.2 mm axial height, and parallel proximal walls with 3 ± 0.2 mm buccolingual width. All samples were divided into five groups (10 each): group I: positive control group (intact teeth), group II: negative control group (prepared unrestored), groups III, IV, and V: prepared and restored with Filtek Z350 XT packable composite resin by using three types of adhesive systems; Adper Single Bond, Clearfil liner Bond F, Single Bond Universal Adhesives respectively. After thermocycling, Specimens were subjected to compressive axial loading, and were tested individually in a universal testing machine. Peak loads at fracture were recorded. Statistical analysis was performed using SPSS, version 20.0. Results All groups were significantly higher than prepared but unrestored teeth with no significant difference was recorded between the three types of adhesives. Conclusion Restoring with packable composite using adhesive system had improved the fracture resistance of teeth subjected to class II mesio‑occluso‑distal preparations. Using the adhesive systems, insignificantly affect fracture resistance of premolars.