Table 2 Assessment of the quality of the studies.

Author, reference (year)	Selection			Comparability		Outcome assessment		Score
	1	2	3	4	5	6	7
Ricci15 (2001)	*	*	*	*		*	*	******
Meharwal16 (2002)	*	*	*	**	**	*	*	*********
Hirose17 (2001)		*	*	**		*	*	******
Al‐Ruzzeh18 (2001)		*	*	*	*	*	*	******
Koutlas19 (2000)	*	*			*	*	*	*****
Demaria20 (2002)	*	*	*	**	*	*	*	********
Beauford8 (2003)	*	*	*	**		*	*	*******
Hoff21 (2002)	*	*	*	*	*	*	*	*******
Lin9 (2003)		*	*	**		*	*	******
Boyd22 (1999)		*	*	*	**	*	*	*******
Ascione23 (2002)	*	*	*			*	*	*****
D'Alfonso10 (2004)	*	*	*	**		*	*	*******
Shimokawa11 (2003)		*	*	**		*	*	******
Deuse12 (2003)	*	*	*	*	*	*	*	*******