Table 2.

Risk-of-bias assessment of selected studies following the Cochrane Handbook for Systematic Review of Interventions.

	Random Sequence Generation (Selection Bias)	Allocation Concealment (Selection Bias)	Blinding of Participants (Performance Bias)	Blinding of Outcome Assessment (Detection Bias)	Incomplete Outcome Data (Attrition Bias)	Selective Reporting (Reporting Bias)	Other Bias
Thie et al. (2001) [24]	+	+	+	+	+	+	?
Haghighat et al.(2013) [25]	?	?	–	–	+	+	+
Damlar et al. (2015) [26]	?	+	+	+	+	+	+
Nguyen et al. (2001) [27]	+	+	+	?	-	+	+
Cahlin et al. (2011) [28]	+	+	+	+	+	+	+
Cen et al. (2018) [29]	+	+	+	+	+	+	+
Yang et al. (2018) [30]	+	+	+	+	+	+	+
Kılıç (2021) [31]	+	?	–	+	+	+	+

“+” = without bias, “–” = with bias, “?” = no information.