Objective: Previous studies have shown a correlation between the clinical performance of adhesive systems and the use of flowable composites. The aim of the present study was to evaluate the difference of micro tensile bond strength (µ-TBS) of three different composite/ adhesive combinations depending on the additional use of the corresponding flowable composite. Methods: In this study twenty-four freshly extracted third molars were included. All teeth were prepared in a special manner allowing the simulation of dentin perfusion. The specimens were randomly assigned to six experimental groups of four samples each: group A: Excite/ Tetric Ceram; group Af: plus Tetric Flow; group B: Clearfil New Bond/ Tetric Ceram; group Bf: plus Tetric Flow; group C: AdheSE/Tetric Flow; group Cf: plus Tetric Ceram. All materials were applied in a standardized class II cavity. After 24 h in water, the specimens were cut perpendicularly with a low-speed diamond saw to obtain sticks with a surface area of 1mm2 (n=15). The µ-TBS was measured using a Bencor device in an universal testing machine. Results: Following µ-TBS were evaluated (mean value and standard deviation printed in MPa):
| | A | Af | B | Bf | C | Cf |
| Mean | 18.27 | 26.82 | 22.82 | 24.23 | 20.34 | 21.97 |
| SD | 6.09 | 6.68 | 5.82 | 7.95 | 6.89 | 6.55 |
Statistical analysis revealed significant differences between the six groups (p< 0.001, ANOVA). The additional use of the flowable composite resulted only in group Af in significant higher values (p< 0.001, Tukeys test). Between the groups Af and Bf as well as between Bf and Cf no significant differences could be detected. The values in group Cf were significantly decreased compared to group Af (p< 0.001, Tukeys test). Conclusion: Within the limitations of the present in vitro investigation it can be concluded that the additional use of flowable composites increased µ-TBS only in the case of Excite.