Table 2.

Risk of bias within trials

Study or subgroup	Random sequence generation	Allocation concealment	Blinding: participants and personnel	Incomplete outcome data	Overall risk
Crooks 2006 [16]	unclear	unclear	unclear	adequate	high
Crooks 2010 [17]	unclear	unclear	unclear	adequate	high
Jones 2014 [14]	unclear	unclear	unclear	adequate	high
Shing 2007 [18]	adequate	adequate	adequate	adequate	low
Shing 2013 [19]	adequate	adequate	adequate	unclear	moderate