Summary: The function of a sealer is to improve the seal between guttapercha and dentinal wall. In warm techniques, it should compensate for the shrinkage of guttapercha. The aim of this study was: (1.) to compare the importance of sealer application in both lateral compaction and Thermafil and (2.) to compare the tightness of apical seal, performed by sealer Apexit in both techniques. The extracted teeth were instrumented by K-f"iles and a step back technique, up to ISO 40 master apical f"ile. Teeth were obturated and immersed in 1 % methylene blue for one week. The results in groups without sealer revealed signif"icantly higher (p < 0.001) penetration than with a sealer. Moreover, lateral compaction without sealer performed signif"icantly worse than Thermafil (p = 0.01). The quality of apical seal in both techniques with Apexit was comparable (p > 0.05). Apexit performed best while being applicated as a sole obturating material. However, long term results should be considered, due to high solubility of calciumhydroxide based sealers.

        Key words: Thermafil - lateral compaction - leakage - sealer - Apexit