Table 2.

Risk of bias summary for each included study.

Study, Year	Random Sequence Generation	Allocation Concealment	Blinding Participants	Blinding of Outcome Assessment	Incomplete Data	Selective Reporting	Other Bias	Risk of Bias
Arenas 1991	+	+	+	+	+	+	+	Low risk
Arenas 1994	+	+	+	+	+	+	+	Low risk
Bradasawi 2016	+	+	+	+	+	+	+	Low risk
Brass 1994	+	+	+	+	+	+	+	Low risk
Colombani 1996	+	+	+	+	+	+	+	Low risk
Chun 2011	+	+	-	-	+	+	+	Low risk
Cooper 1986	-	-	-	-	+	+	-	High risk
Dragan 1987	+	+	+	+	+	+	+	Low risk
Dragan 1988	+	+	+	+	+	+	+	Low risk
Giamberardino 1996	+	+	+	+	+	+	+	Low risk
Gorostiaga 1989	-	-	+	+	+	+	+	Low risk
Greig 1987	+	+	+	+	+	+	+	Low risk
Huertas 1992	+	+	+	+	+	+	+	Low risk
Koozehchian 2018	+	+	+	+	+	+	+	Low risk
Malaguarnera 2007	+	+	+	+	+	+	+	Low risk
Marconi 1985	+	+	-	-	+	+	+	Low risk
Mor 2018	+	+	+	+	+	+	+	Low risk
Muller 2002	-	-	-	-	+	+	+	High risk
Natali 1993	+	+	-	-	+	+	+	Low risk
Nuesch et al.1999	-	-	-	-	+	+	+	High risk
Orer 2014	+	+	+	+	+	+	+	Low risk
Oyono-Enguelle 1988	-	-	-	-	+	+	+	High risk
Parandak 2014	+	+	+	+	+	+	+	Low risk
Siliprandi 1990	+	+	+	+	+	+	+	Low risk
Soop 1988	-	-	+	+	+	+	+	Low risk
Stuessi 2005	+	+	+	+	+	+	+	Low risk
Swart 1997	-	-	-	-	+	+	+	High risk
Vecchiet 1990	+	+	+	+	+	+	+	Low risk
Wachter 2002	-	-	-	-	+	+	+	High risk
Wyss 1990	-	-	+	+	+	+	+	High risk

+: low risk of bias; -: high risk of bias.