Study Random
sequence
generation 		Allocation
concealment 		Blinding of
personnel 		Blinding of
outcome
assessment 		Incomplete
outcome data 		Selective
reporting 		Other
sources of
bias 		Overall
bias
Jiang et al. [62] + ? ? + + + - ?
Nuñez et al. [63] + ? ? + + + - ?
Liu et al. [64] + - - ? - + - -
Jiang et al. [65] + ? ? ? + + - -
Park et al. [66] + ? ? ? - + - -
Suaid et al. [67] + ? ? ? + + - -
Tsumanuma et al. [68] ? ? ? + + + - -
Suaid et al. [69] + - + ? - + - -
Khorsand et al. [70] + ? ? ? - + - -
Tobita et al. [71] ? ? ? ? - + - -

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