Table 2.

Assessment of risk of bias in the included studies using Cochrane criteria

Study	Reference	Sequence generation	Allocation concealment	Blinding of participants and personnel	Blinding of outcome assessment	Incomplete outcome data	Selective outcome reporting	Other potential threats to validity
Eshtehardi et al. 2012	[21]	H	H	H	H	L	L	L
Guo et al. 2012	[22]	U	U	H	H	L	L	L
Hong et al. 2009	[23]	U	U	H	H	L	L	L
Hwang et al. 2013	[24]	H	H	H	L	L	L	H
Lee et al. 2012	[14]	L	L	L	L	L	L	L
Nasu et al. 2009	[25]	H	H	H	H	L	L	L
Nozue et al. 2012	[26]	L	L	H	L	L	L	L
Puri et al. 2014	[27]	U	U	H	H	L	L	L
Taguchi et al. 2013	[28]	H	H	H	H	L	L	L

H, high risk of bias; L, low risk of bias; U, unclear risk of bias