Table 2 The mineral density (g cm^− 3) in the lesion area at baseline, after the development of ARCLs, and following 13 days pH-cycling (± SD), mean differences and p-value, with the percentage of mineral change for all groups at the tooth surface

Group 1. Deionised water

1.04 ± 0.34

0.75 ± 0.30

0.63 ± 0.18

-0.12 ± 0.27

0.003

-0.07 ± 0.10 (7% decrease)

Kruskal-Wallis H, H [3] = 125.310, p < 0.001, all intergroups comparison (p < 0.001)

1.48 ± 0.19

0.51 ± 0.15

0.42 ± 0.13

-0.09 ± 0.05

< 0.001

1.33 ± 0.08

0.73 ± 0.19

0.73 ± 0.11

0.003 ± 0.16

0.006

Group 2. BG with 540 ppm

1.32 ± 0.10

0.85 ± 0.24

0.80 ± 0.13

-0.05 ± 0.17

0.130

0.11 ± 0.10 (11% increase)

1.26 ± 0.18

0.77 ± 0.21

0.84 ± 0.08

0.07 ± 0.18

0.010

1.20 ± 0.18

0.66 ± 0.16

0.96 ± 0.12

0.30 ± 0.15

< 0.001

Group 3. 1,450 ppm

1.21 ± 0.12

0.83 ± 0.19

0.96 ± 0.10

0.13 ± 0.18

< 0.001

0.30 ± 0.07

(30% increase)

1.38 ± 0.11

0.45 ± 0.13

0.86 ± 0.24

0.41 ± 0.13

< 0.001

1.33 ± 0.07

0.64 ± 0.06

0.99 ± 0.07

0.35 ± 0.05

< 0.001

Group 4. 5,000 ppm

1.24 ± 0.17

1.04 ± 0.22

1.08 ± 0.22

0.04 ± 0.20

0.003

0.22 ± 0.10 (22% increase)

1.26 ± 0.13

0.71 ± 0.17

1.04 ± 0.13

0.33 ± 0.17

< 0.001

1.26 ± 0.20

0.72 ± 0.13

1.00 ± 0.18

0.28 ± 0.10

0.006