Objective: To assess the ability of sodium fluoride containing dentifrices to protect human enamel against demineralization induced by dietary acid buffers. Methods: Enamel solubility reduction (ESR) studies were based on method #33 described in the US Food and Drug Administration testing procedures with the following modifications. Briefly, human molars were treated with centrifuged supernatants produced from 1 part by weight test dentifrice and 3 parts water for 5 minutes with agitation. Pre and post treatment etchings were performed with 1% citric acid pH 3.8, 0.85% tartaric acid pH 3.1 or 6% acetic acid pH 2.4 for 12, 4 or 2 minutes respectively at 37°C with agitation. The etching times were chosen to give a similar pre-etch phosphate concentration. A fluoride free dentifrice, an anti-caries dentifrice containing sodium fluoride (NaF) at 1100ppm fluoride and a test dentifrice containing NaF at 1150ppm fluoride were examined. The results are expressed as a percentage reduction of the pre-etch phosphate concentrations. Results:
Effect of Dentifrice Treatment on the %ESR
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Dentifrice %ESR* |
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Etching Solution |
Fluoride free |
Anti-caries |
Test |
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Citric acid pH 3.8 |
-7.2 (0.9) |
10.2 (1.5) |
13.6 (1.1) |
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Tartaric acid pH 3.1 |
-2.0 (0.9) |
13.7 (1.5) |
17.0 (1.2) |
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Acetic acid pH 2.4 |
-4.2 (1.0) |
14.2 (1.2) |
17.0 (1.0) |
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*n=12 (standard error in brackets) |
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Both sodium fluoride containing dentifrices conferred significant protection against acid demineralisation versus the fluoride free control (p<0.05). The results for the test dentifrice were numerically higher than for the anti-caries dentifrice (p=0.05, 0.06 and 0.07 for the citric acid, tartaric acid and acetic acid experiments respectively). Conclusion: This study demonstrated that the treatment of human enamel in vitro with sodium fluoride dentifrices can reduce subsequent demineralization by buffered solutions representative of dietary acids.