Table 1.

Quality assessment.

Author and Date of Publication	Case Definition	Selection of Controls	Matched for Bias	Assessment of Outcome	Score	Quality
Albertini et al., 2015 [36]	2	2	0	0	4	Medium
Alcoforado 1990 [37]	1	0	0	0	1	Low
Arisan et al., 2015 [38]	2	0	0	0	2	Low
Ata-Ali et al., 2015 [39]	2	1	1	0	4	Medium
Augthun et al., 1997 [40]	1	0	0	0	1	Low
Bassetti et al., 2014 [41]	2	0	0	0	2	Low
Becker et al., 1990 [42]	1	0	0	0	1	Low
Bertone et al., 2016 [43]	2	0	0	0	2	Low
Birang et al., 2017 [44]	2	0	0	0	2	Low
Bombeccari 2013 [45]	2	0	0	0	2	Low
Botero et al., 2005 [46]	2	1	2	0	5	Medium
Caccianiga et al., 2016 [47]	1	0	0	0	1	Low
Canullo et al., 2013 [48]	2	1	2	0	5	Medium
Canullo et al., 2015a [49]	2	0	0	0	2	Low
Canullo et al., 2015b [50]	2	1	2	0	5	Medium
Canullo et al., 2017 [51]	2	1	2	0	5	Medium
Casado et al., 2011 [52]	1	1	2	0	4	Medium
Charalampakis et al., 2012 [53]	2	0	0	0	2	Low
Cortelli et al., 2013 [54]	2	2	2	0	6	High
da Silva et al., 2014 [55]	2	1	2	0	5	Medium
Dabdoub et al., 2013 [56]	2	2	2	0	6	High
de Waal et al., 2014 [57]	2	0	0	0	2	Low
de Waal et al., 2017 [58]	2	1	2	0	5	Medium
Dörtbudak et al., 2011 [59]	2	0	0	0	2	Low
Ebadian et al., 2012 [60]	2	1	2	1	6	High
Faveri et al., 2011 [61]	2	1	2	0	5	medium
Gurlek et al., 2017 [62]	2	2	2	0	6	high
Hultin et al., 2002 [63]	1	1	2	0	4	medium
Isehed et al., 2016 [64]	2	0	0	0	2	low
Jankovic et al., 2011 [65]	2	1	2	0	5	medium
Kumar et al., 2012 [66]	2	1	2	0	5	medium
Leonhardt et al., 1999 [67]	2	1	2	0	5	medium
Leonhardt et al., 2003 [68]	2	0	0	0	2	low
Maruyama et al., 2014 [69]	2	2	2	0	6	high
Maximo et al., 2009 [70]	2	1	2	1	6	high
Mombelli et al., 2001 [71]	2	0	0	0	2	low
Neilands et al., 2015 [72]	2	1	1	1	5	high
Parthiban et al., 2017 [73]	2	1	1	0	4	medium
Passariello et al., 2012 [74]	1	0	0	0	1	low
Persson et al., 2006 [75]	1	0	0	0	1	low
Persson et al., 2010 [76]	2	0	0	0	2	low
Persson et al., 2011 [77]	2	0	0	0	2	low
Renvert et al., 2006 [78]	2	0	0	0	2	low
Renvert et al., 2007 [79]	2	1	2	0	5	medium
Renvert et al., 2009 [80]	2	0	0	0	2	low
Renvert et al., 2015 [10]	1	0	0	0	1	low
Renvert et al., 2017 [81]	2	0	0	0	2	low
Salcetti et al., 1997 [82]	1	1	1	1	4	medium
Sato et al., 2011 [83]	2	0	0	0	2	low
Sbordone et al., 1995 [84]	2	0	0	0	2	low
Schmalz et al., 2016 [85]	2	1	1	0	4	medium
Schwarz et al., 2015 [86]	2	1	1	0	4	medium
Shiba et al., 2016 [87]	2	2	2	0	6	high
Shibli et al., 2008 [88]	2	1	2	0	5	medium
Tada et al., 2017 [89]	2	0	0	0	2	low
Tsigarida et al., 2015 [90]	1	1	1	0	3	medium
Verdugo et al., 2015 [91]	2	2	2	0	6	high
Zhuang et al., 2016 [92]	2	2	2	0	6	high
Ziebolz et al., 2017 [93]	2	1	2	0	5	medium