Table 2.

Selection Criteria

Inclusion criteria	1. Participants: Freshly extracted single rooted human teeth with closed apices, and after standard root canal preparation, all specimens had regular space for obturation.
	2. Intervention: Root canals were obturated with Gutta-percha/AH plus and (or) the Resilon system.
	3. Control: Unprepared and unfilled roots (negative control roots) or prepared but unfilled roots (positive control roots).
	4. Outcomes: Vertical fracture resistance of roots.
	5. Study design: Randomized controlled in vitro trials.
Exclusion criteria	1. Studies that did not fulfill the inclusion criteria.
	2. .Studies that evaluated the influence of different factors on the resistance to fracture of endodontically treated roots obturated with Gutta-percha/AH plus or the Resilon system.
	3. Retreatment.