Inhibition of Dietary Acid-Mediated Enamel Demineralisation by Sodium Dodecyl Phosphate

Objectives:  To evaluate sodium dodecyl phosphate (SDP) as an inhibitor of acid-mediated demineralisation of human enamel.  Methods:  Efficacy was evaluated using modified versions of the FDA monographed Enamel Solubility Reduction (ESR) method #33.  Method #33 employs 0.10M lactic acid pH4.5 to simulate a bacterial acid challenge.  The present studies employed 1.0% w/w lactic, citric or phosphoric acid at pH3.75 as the erosive challenge, with spectrophotometric quantitation of released phosphate or calcium.  Inhibition by SDP (Nikko Chemicals, Japan) was compared to deionised water, fluoride (as NaF), sodium hexametaphosphate (Sigma-Aldrich) and a 1:3w/w slurry of US Crest^" Cavity Protection in deionised water.  Treatments, except the dentifrice slurry, were adjusted to pH7.0 prior to use.  Each group of enamel specimens (n=14) was treated for 300s between the first and second acid exposure.  Results:  Directional efficacy within each model variant was similar, with SDP³Fluoride>0.11% fluoride dentifrice>NaHMP. The results are tabulated below, with the different statistical groups designated by superscripts.  Treatment with 0.50% SDP conferred the greatest protection against acid-mediated enamel dissolution, splitting statistically from water in all models (p>0.05; Student Newman-Keuls).  The 0.030% fluoride positive control was statistically superior to water against lactic and citric acid, and directionally superior to water, NaHMP and the fluoride dentifrice against phosphoric acid.  The protection offered by the 0.50% NaHMP treatment against the three acid challenges was not statistically different to water.  Conclusion:  A 0.50% SDP solution was shown to be at least as effective as 0.030% fluoride at inhibiting dietary acid-mediated demineralisation of human enamel in the present in vitro models.