This study was performed to evaluate the anticarious effect of several topical fluoride agents(NaF, NH4F, TiF4) by solution pH and application time. Bovine enamel specimen and synthetic hydroxyapatite were treated with 5 kinds of 1,O00ppm fluoride solutions(NaF, NH4F : pH 2.0, 6.5 : TiF4 : pH 2.0) for 5 min, 60 min, and 12 hr, respectively.
Bovine enamel specimens treated with fluoride solutions were evaluated for enamel solubility by atomic absorption spectroscopy. The amount of fluoride adsorbed in synthetic hydroxyapatite was measured by specific electrode. The results were as follows
1. In NaF, NH4F group, fluoride adsorptions at pH 2.0 solution were 228.7--262.6mg/m2, 235.4266.8mg/m2 and at pH; 6.5 solution, 18.3141.9mg/m2, 42.1164.3mg/m2, respectively. Fluoride adsorption at pH 2.0 solution was higher than at pH 6.5 solution.
2. In group treated for 12 hr, fluoride adsorptions of NaF, NH4F group at pH 2.0 solution were 262.6, 266.8mg/m2, respectively, and higher than those of other fluoride groups. That of TiF4 group was 87.1mg/m2, and lower than other fluoride groups.
3. Among enamel specimens treated for 1:2 hr, enamel solubility of TiF4 group was 0.167mg/cm2 24h, and that ,f ´other fluoride groups were 02140.236mg/cm2 24h. TiF4 group showed lower enamel solubility than other fluoride groups.
4. Among enamel specimens treated with NO, NH4F solution for 5 and 60 min, that treated with pH 2.0 solution showed lower enamel solubility than did with pH 6.5 solution. But the differences between those treated for 12 hr were not significant.
5. In NaF, NH4F group, changes in fluoride adsorption and enamel solubility by application time were higher at pH 6.5 solution than at pH 2.0 solution.
In conclusion, NaF, NH4F applicated for a short time in an acidic solution, but for a long time, in a neutral solution were effective on fluoride adsorption and acid resistance. TiF4 showed the effective acid resistance though applicated for a short time.
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