Table 1 Mean ± Standard Deviation (SD) of microhardness values of intact, demineralized, and remineralized enamel and microhardness recovery (%) of the study groups at different enamel depths

30 μm

0.5% gallic acid

215.38 ± 43.57

121.79 ± 34.02

185.8 ± 48.55

73.98 ± 41.85

< 0.001*

2% gallic acid

276.25 ± 38.88

130.83 ± 37.81

164.67 ± 36.11

29.55 ± 12.21

8% gallic acid

278.95 ± 40.75

139.93 ± 38.82

186.74 ± 49.27

40.35 ± 25.68

Fluoride

263.22 ± 32.61

116.80 ± 34.01

165.46 ± 50.94

38.15 ± 10.68

Control

254.48 ± 28.48

115.85 ± 22.41

114.30 ± 22.88

-1.83 ± 6.60

75 μm

0.5% gallic acid

244.46 ± 36.36

189.93 ± 45.43

222.60 ± 42.53

40.18 ± 90.28

0.264

2% gallic acid

277.88 ± 27.53

216.17 ± 58.05

217.15 ± 46.71

41.09 ± 15.75

8% gallic acid

296.98 ± 31.08

227.52 ± 58.18

251.55 ± 39.52

23.02 ± 28.40

Fluoride

275.61 ± 30.91

205.83 ± 36.52

221.49 ± 40.27

38.87 ± 35.13

Control

271.32 ± 29.56

213.06 ± 30.65

203.01 ± 55.29

30.63 ± 11.40

120 μm

0.5% gallic acid

270.51 ± 41.51

231.65 ± 46.37

261.04 ± 31.35

74.89 ± 5.66

0.065

2% gallic acid

290.09 ± 21.76

257.20 ± 50.50

256.83 ± 27.03

67.82 ± 58.01

8% gallic acid

307.33 ± 35.20

271.85 ± 62.19

281.65 ± 51.54

22.10 ± 61.69

Fluoride

287.42 ± 27.22

265.22 ± 24.39

268.96 ± 22.83

21.66 ± 41.81

Control

287.41 ± 22.76

261.88 ± 31.17

230.11 ± 34.73

20.71 ± 70.52