Study Year of
publication 		Random
sequence
generation 		Allocation
concealment 		Blinding of
participants
and personnel 		Blinding of
outcome
assessment 		Incomplete
outcome
data 		Selective
reporting 		Other
sources of
bias
Kuchler et al. [14] 2011 + + + ? + + +
Mozzati et al. [15] 2015 - + + + + + +
Holahan et al. [16] 2009 - + + + - + +
Shibli et al. [17] 2007 - ? + + + + +
Kwon et al. [18] 2012 - - ? + + + +
Siebert et al. [19] 2015 ? ? + + ? + +
Jacobsen et al. [20] 2012 + + + + + + +
Shabestari et al. [21] 2009 ? + + + + + +
Lopez-Cedrum et al. [22] 2013 + + + + + ? +
Goss et al. [23] 2010 - - + + ? + +
Koka et al. [24] 2010 + + + + - + +
Zahid et al. [25] 2011 + + + + + + +
Grant et al. [26] 2008 + + + + - + +
Lazarovici et al. [27] 2010 + + + + + + +
Griffiths et al. [28] 2012 + + + + + + +
Martin et al. [29] 2010 + ? + + ? + +
Bell et al. [30] 2010 + + + + + + +
Fugazzotto et al. [31] 2007 + + + + + + +
Alsaadi et al. [32] 2007 ? + + + ? + +
Turkyilmaz et al. [33] 2010 - - + + + + +
Anner et al. [34] 2010 + + + + ? ? +
Oates et al. [35] 2009 - ? + + ? + +
Dowell et al. [36] 2007 - + + + + + +
Tawil et al. [37] 2008 - - + + + + +
Khandelwal et al. [38] 2011 + + + + + + +
Oliveira et al. [39] 2011 - - + + + + +
Stevenson et al. [40] 2007 - ? + + + + +
Krennmair et al. [41] 2010 + + + + + + +
Welnalder et al. [42] 2010 + + + + + + +
Carr et al. [43] 2010 ? ? + + - + +
Hernandez et al. [44] 2012 - - + + + + +
Lopez-Jornet et al. [45] 2014 + + + + + + +
Czerninski et al. [46] 2013 + ? + + ? + +
Alsaadi et al. [47] 2008 ? ? + + + + +
Montebugnoli et al. [48] 2012 - - + + + + +
Korfage et al. [49] 2015 + + + + + + +
Guckes et al. [50] 2002 ? ? + + ? + +
Alsaadi et al. [51] 2008 + + + + ? + +
Souza et al. [52] 2013 + + + + + + +
Krennmair et al. [53] 2016 - ? + + + + +
Renvert et al. [54] 2013 + + + + + + +

+ = low risk of bias; ? = unclear risk of bias; - = high risk of bias.