Effect of Flowable Composite on the Dentinal Bond Strength of Packable Composite Following Thermal and Mechanical Cycling

Due to high viscosity، adaptation of packable composite to cavity walls is doubtful. This study investigates the effect of flowable composite liner on the dentinal bond strength of packable composite after thermal and mechanical cycling and its comparison with hybrid composites. In this experimental study، Single Bond was applied on the dentinal surface of 30 third molars. The teeth were randomly divided into three groups: In group I، P60 with Filtek Flow، in Group II، composite P60 alone، and in Group III، composite Z100 were used. After thermocycling، each group was randomly divided into two sub-groups (control and experimental) and only experimental subgroups were tested under load cycling (50 Newton، 100000 load cycles). Microtensile bond strength of all samples was measured and the failure mode was examined with a stereomicroscope. The results were statistically analyzed by Kurskal Wallis، Mann Whitney and Fisher’s Exact test. Before load cycling، the mean bond strength and standard deviation of group 1 was 25. 49±2. 35، group 2 was 35. 63±3. 57 and group 3 was 30. 61±5. 56 MPa، which was statistically significant (P<0. 05). After load cycling، the mean bond strength and standard deviation of group 1 was 24. 37±1. 42، group 2 was 31. 36±2. 63 and group 3 was 26. 87±9. 16 MPa. The difference was not statistically significant. The difference between control and experimental groups was not statistically significant in any of the materials. Flowable composite liner was not effective on the bond strength of packable composite to dentin and it was the same as hybrid composite pre and post cycling.