Table 2. Risk of bias assessment based on Cochrane Collaboration criteria.

Study	Random sequence generation	Allocation concealment	Blind method	Data integrity	Optional reporting	Other bias
Bin-Nun et al., 2005 (11)	Low	Unclear	Unclear	Low	Low	Low
Lin et al., 2008 (12)	Low	Low	Low	Low	Low	Low
Samanta et al., 2009 (13)	Low	Low	Low	Low	Low	Low
Braga et al., 2011 (14)	Low	Low	Low	Low	Low	Low
Sari et al., 2011 (15)	Low	Low	Low	Low	Low	Low
Demirel et al., 2013 (16)	Low	Low	Low	Low	Low	Low
Fernández-Carrocera et al., 2013 (17)	Low	Unclear	Unclear	Low	Low	Low
Oncel et al., 2014 (18)	Low	Low	Low	Low	Low	Low
Van Niekerk et al., 2015 (19)	Low	Low	Low	Low	Low	Low
Costeloe et al., 2016 (20)	Low	Low	Low	Low	Low	Low