Table 3. Assessment of risk of bias for the clinical trials included.
| Questions to be considered | |||||||
|---|---|---|---|---|---|---|---|
| Study | Random sequence generation | Allocation concealment | Blinding of participants and personnel | Blinding of outcome assessment | Free of incomplete outcome data | Free from baseline imbalance | Other sources of bias |
| Louw et al. (2002) | YES | UNCLEAR | NO | UNCLEAR | UNCLEAR | UNCLEAR | UNCLEAR |
| Taifour et al. (2002) | YES | UNCLEAR | UNCLEAR | UNCLEAR | UNCLEAR | UNCLEAR | UNCLEAR |
| Honkala et al. (2003) | YES | UNCLEAR | NO | NO | UNCLEAR | UNCLEAR | UNCLEAR |
| Yu et al. (2004) | YES | UNCLEAR | UNCLEAR | UNCLEAR | UNCLEAR | UNCLEAR | UNCLEAR |
| van den Dungen et al. (2004) | YES | UNCLEAR | NO | YES | UNCLEAR | UNCLEAR | UNCLEAR |
| Ersin et al. (2006) | YES | UNCLEAR | UNCLEAR | YES | UNCLEAR | UNCLEAR | UNCLEAR |
| Innes et al. (2011) | YES | YES | NO | NO | UNCLEAR | UNCLEAR | UNCLEAR |
| Mijan et al. (2014) | YES | NO | NO | NO | UNCLEAR | UNCLEAR | UNCLEAR |
| Santamaria et al. (2014) | YES | YES | NO | NO | UNCLEAR | UNCLEAR | UNCLEAR |
| Borges et al. (2012) | YES | YES | UNCLEAR | UNCLEAR | UNCLEAR | UNCLEAR | UNCLEAR |
| Hesse et al. (2014) | YES | UNCLEAR | UNCLEAR | UNCLEAR | UNCLEAR | UNCLEAR | UNCLEAR |
| Santos et al. (2012) | YES | UNCLEAR | NO | NO | UNCLEAR | UNCLEAR | UNCLEAR |
| Zhi et al. (2012) | YES | UNCLEAR | UNCLEAR | YES | UNCLEAR | YES | UNCLEAR |
| Duangthip et al. (2016) | YES | UNCLEAR | YES | YES | YES | YES | UNCLEAR |