Table 2.

Methods and results of included studies.

Included studies	Randomization	Allocation concealment	Blinding	Incomplete outcome data	Selective outcome reporting	Other sources of bias
1 Burkard T 2011	Retrospective	Unclear	Unclear	No	No	No
2 Rolf P. Kreutz 2010	Retrospective	Unclear	Unclear	No	No	No
3 Robert a Rossini-2010	Yes	Unclear	No	No	No	No
4 Ekta G 2010	Retrospective	Unclear	Unclear	No	No	No
5 Evanchan 2009	Retrospective	Unclear	No	No	No	No
6 Hiroshi Y 2009	Retrospective	Unclear	Unclear	No	No	No
7 Kishore J 2011	Yes	Unclear	Unclear	No	No	No
8 Michael 2010	Yes	Unclear	Unclear	No	No	No
9 Takeo-2010	Retrospective	Unclear	Unclear	No	No	No
10 O' Donoghue 2009	Yes	Unclear	Unclear	No	No	No
11 Rahel H 2012	Retrospective	Unclear	No	No	No	No
12 Jian Jun zou-2014	Retrospective	Unclear	Unclear	No	No	No
13 Subhash 2010	Yes	Unclear	No	No	No	No
14 Zarris 2009	Yes	Unclear	Unclear	No	No	No
15 Jolanta M-2008	Yes	Unclear	Unclear	No	No	No