Abstract Background The durability of bonded CAD/CAM restorations depends largely on effective adhesion to dentin. Immediate dentin sealing (IDS) has been proposed to enhance bonding effectiveness compared with conventional delayed dentin sealing (DDS). Additionally, while resin cements remain the gold standard for luting, flowable composites have emerged as potential alternative. This study aimed to evaluate the effect of different dentin sealing techniques and luting materials on the microtensile bond strength (µTBS) of CAD/CAM composite disc to dentin after immediate and long-term aging. Methods Twenty flat dentin specimens were obtained from extracted human molars and randomly assigned to two main groups according to the dentin sealing techniques into (group 1: No-IDS and group 2: IDS with a universal adhesive). The two groups were provisionally restored with temporary materials for two weeks. Afterwards the temporary materials were removed, and surface was reactivated with air borne abrasion. Each group was subdivided according to the luting material used for CAD/CAM composite discs into (subgroup 1: dual-cure self-adhesive resin cement and subgroup 2: submicron hybrid flowable composite). The specimens were sectioned into micro-bars and tested for µTBS either after 48 h (immediate) or 6 months (long-term aging) in water storage. Data were analyzed using three-way ANOVA and post-hoc comparisons (α = 0.05). Failure modes were analyzed. Results Immediate µTBS values displayed no significant differences among the tested groups. Following long-term aging, IDS combined with a flowable composite yielded significantly higher µTBS compared to groups without IDS. Furthermore, the flowable composite demonstrated significantly higher bond strength than the self-adhesive resin cement, regardless of the dentin sealing protocol used. Conclusions The microtensile bond strength of CAD/CAM composite to dentin is dependent on both the dentin sealing technique and the luting material. Immediate dentin sealing combined with a submicron hybrid flowable composite demonstrated the highest bond strength after long-term aging, compared to the tested self-adhesive resin cement. The effect of artificial aging was highly material-dependent; therefore, long-term aging is necessary to accurately evaluate the bond durability.
Abo-Eldahab et al. (Mon,) studied this question.