Chlorhexidine (CH) is cationic and it forms salts of low solubility with anions such as phosphate, sulfate and carboxyl. Toothpastes contain anionic detergents, one of the most widely used being sodium lauryl sulfate (SLS). The aim of the present study was to examine the possible interaction between CH and the anion SLS in vivo. The interference of SLS on the antiplaque potential of CH was investigated. The study was performed according to a single blind cross over design, and the effect of the interval between prerinsing with an aqueous solution of SLS and the subsequent rinsing with CH was examined. The antiplaque effect was examined by the use of the Silness and Löe plaque-index. The results showed that even a 30-min interval between SLS- and CH-rinsing gave a significantly reduced antiplaque effect of CH, whereas the neutralizing effect of SLS disappeared after 2 h. It can thus be concluded that SLS is not compatible with CH, even when these compounds are introduced separately in the oral cavity. The time between toothbrushing and a CH rinse should at least be 30 min, if a reduction in the antimicrobial effect is to be avoided.

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