Table 3 MINORS bias scale

Clearly stated aim

2

2

2

2

2

2

2

2

2

2

2

2

2

Contemporary groups

2

2

2

2

2

2

2

2

2

2

2

2

2

Prospective collection of data

2

2

2

2

2

2

2

2

2

2

2

2

2

Sample randomization

0

0

2

0

0

0

0

0

0

2

2

2

0

Test group: Zn content in the materials: 0 (not reported), 1 (materials coated with Zn or rough mixing ratio of Zn), 2 (precise mixing ratio of Zn)

2

1

2

2

1

2

1

1

2

2

2

2

1

Measurements standardization

2

2

2

2

2

2

2

2

2

2

2

2

2

Condition of the samples during measurements

2

2

2

2

2

2

2

2

2

2

2

2

2

Measurements method

2

2

2

2

2

2

2

2

2

2

2

2

2

Endpoints appropriate to the aim of the study

2

2

2

2

2

2

2

2

2

2

2

2

2

Unbiased assessment of the study endpoint

0

0

0

0

0

0

0

0

0

0

0

0

0

Baseline equivalence of groups

2

2

2

2

2

2

2

2

2

2

2

2

2

Adequate statistical analyses

2

2

0

2

2

2

2

2

2

2

2

2

0

Total Score

20

19

20

20

19

20

19

19

20

22

22

22

17