Purpose: To test the influence of thermomechanical loading and mode of cleaning the pulp chamber on coronal microleakage of adhesive sealings over root canal fillings. Materials and Methods: Root canals of molars were instrumented to size 60 taper .02 and filled with AH plus (Dentsply DeTrey) and a single gutta-percha cone size 55 taper .02. After removal of residual sealer with an alcoholmoistened foam pellet, different pretreatments were performed: groups 1 and 5: no further pretreatment; groups 2 and 6: use of a water cooled high-speed diamond bur; groups 3 and 7: etch-and-rinse with 37% H3PO4 for 10 s; groups 4 and 8: diamond bur and etching. Then Syntac (Ivoclar Vivadent) and two consecutive layers of Tetric flow (Ivoclar Vivadent) were applied. After placing glass-ionomer cement as a provisional restoration, teeth of groups 5 to 8 were additionally subjected to thermomechanical loading (chewing simulation of 200,000 cycles/50 N) and thermocycling (2880 cycles between 5°C and 55°C). A dye penetration test (methylene blue dye 5%, centrifugation for 3 min at 30 G) was used to evaluate linear dye penetration and dye penetration area. Statistical tests were performed using SPSS Win 12.0 (Kolmogorov-Smirnov test, two-way ANOVA, t-test). Results: Thermomechanical loading (TML) had a negative impact on coronal seal (two-way ANOVA, p 0.001). Among TML groups, group 7 (etch-and-rinse) performed best, exhibiting the least influence of TML. Conclusion: For adhesive sealing of the pulp chamber floor, the etch-and-rinse technique combined with a flowable resin composite showed promising results. Nevertheless, a stabilizing restoration should be placed as soon as possible. Keywords: AH plus, dentin bonding, root canal filling, secondary protective seal, Syntac, Tetric flow, thermomechanical loading