The Effect of Liner Placement under Bulk-Fill Resin Composite Restorations on Cuspal Deflection in Maxillary Premolar Teeth.

Purpose: This study investigated the cuspal deflection in premolar teeth restored with different bulk-fill resin composites or without using a liner. Materials and Methods: 60 extracted human upper were used. The samples this divided into three main groups (20 for each) according to materials used; Each group was subdivided two subgroups presence of Standardized large MOD cavities prepared. distance between reference points on cusp tips measured before restoration universal microscope. Then (Filtek bulk fill, X-tra fil fill Activa Bioactive Restorative Material) liner (Activa base/ liner). Second reading 15 min after completion restorations. All subjected thermal cycling cycler machine. third measured. data statistically analyzed Kolmogorov-Smirnov Shapiro-Wilk tests. Results: no significant difference found mean showed significantly higher value than Conclusion: placement base/liner beneath composite restorations decreased deflection.