Table 2.

Risk of bias assessment for the seven included randomized controlled trials according to the Cochrane Collaboration tool.

	Random sequence	Allocation concealment	Blinding pts & personnel	Blinding outcome assessment	Incomplete outcome data	Selective reporting	Other bias
Vardi	+	?	+	+	-	+	+
Srini	?	?	+	+	+	+	-
Yee	+	?	+	+	?	+	+
Olsen	?	+	+	+	+	+	+
Kitrey	?	?	+	+	+	+	+
Kalyvianakis	+	?	+	+	+	+	+
Fojecki	+	+	+	+	+	+	+