Adhesive obturation systems have been introduced in endodontics in an attempt to obtain a "monoblock" in which the core material, sealing agent and root canal dentin form a single cohesive unit within the root canal. This study hypothesis was that adhesive root canal filling systems form a monoblock and obtained a superior adhesiveness to root canal dentin than nonadhesive root canal filling systems. Therefore, this in-vitro study was done to evaluate the bond strength of the four obturation systems to root canal dentin prepared by hand instrumentation using push-out test at different root canal levels.