Table 1.

Risk of bias among the studies

	Random sequence generation (selection bias)	Allocation concealment (selection bias)	Blinding of participants and personnel (performance bias)	Blinding of outcome assessment (detection bias)	Incomplete outcome data addressed (attrition bias)	Selective reporting (reporting bias)	Other bias
Pasqualini et al., 2015	+	+	+	+	+	+	+
Nekoofar et al., 2015	+	+	+	?	+	+	+
Neelakantan et al., 2015	+	+	+	?	+	+	+
Revas et al., 2016	+	+	+	+	+	+	+
Kherlakian et al., 2016	+	+	+	?	+	+	+
ÇiÇek et al., 2016	+	-	+	+	+	+	+
Krithikadatta et al., 2016	+	+	+	+	?	+	+
Zand et al., 2016	+	+	+	+	+	+	+
Mollashahi et al., 2017	+	-	+	+	+	+	+
Shokraneh et al., 2017	+	-	+	+	+	+	+

+: Low risk of bias, ?: Unclear risk of bias, -: High risk of bias