Objective:To observe and compare the inhibitory effect of two fluor protectors with different concentrations on man-made dental caries of human enamel smooth surface and socket in vitro.Methods:Forty smooth surfaces and forty sockets non-carious human enamels were divided into four groups randomly.Each group had ten samples

five samples were employed to experiment

and five samples were used as spare ones.For experiment group(0.5%fluor protector

0.1% fluor protector).the dental enamel surfaces were spreaded 0.5% fluor protector and 0.1% fluor protector twice in series respectively.For positive control group(0.05% NaF)

the dental enamels were dipped into 0.05% NaF for 24h

then taken out and dried.For blank control group(deionized water)

the dental enamels were immersed into deionized water for 24h

then taken out and dried.The specimens were taken out of when they had been immersed into man-made cariogenic fluid(37℃)for 168h

rinsed and dried

then they were divided into two halves by high speed corundum disk in spurting water;one half was used to observe depth of dental caries by polarization microscope

and the other half was employed to observe surface demineralization by scanning electron microscope.Results:The dental Caries depth of 0.5% fluor protector group was the smallest in four groups

and there were significant differences between 0.5% fluor protector group and 0.1% fluor protector group(P<0.05).Conclusion:Two fluor protectors with different concentrations are effective in decreasing the depth of man-made dental caries.But the caries resistance effet of 0.5% fluor protector is better than that of 0.1% fluor protector

s obviously.