The effect of dentifrice quantity and toothbrushing behaviour on oral delivery and retention of fluoride in vivo



While toothpaste F concentration and rinsing regimen have well-characterised impacts on fluoride's effectiveness, other aspects of brushing regimen have much less well-established effects, in particular, dentifrice quantity and brushing duration. An in vivo study (n = 42) of oral fluoride delivery (i.e. oral disposition post-brushing), and retention (i.e. concentration of F in saliva post-brushing, a known efficacy predictor), was performed to compare effects observed with those of dentifrice F concentration and rinsing regimen. Subjects brushed with a NaF-silica dentifrice (Aquafresh Advanced, 1,150 ppm F) or a control dentifrice (250 ppm F, same base), for 45, 60, 120 or 180 seconds with 0.5 or 1.5 g dentifrice, and rinsed with 15 ml water once or three times in a cross-over design. The F concentration was measured in post-brushing expectorate, rinse and toothbrush washing samples, and in saliva between 5–120 minutes after brushing. Using 1.5 g versus 0.5 g dentifrice increased F in all samples: oral retention of F was almost doubled by this increase. Increasing duration of brushing had more complex effects. The amount of F in the expectorate increased but decreased in both rinse and toothbrush washing samples. Oral F retention increased, but only in the period 30–120 minutes after brushing. Over the ranges investigated, the order of importance on oral F retention was: dentifrice F concentration > quantity > rinsing regimen > brushing duration. Hence, increasing dentifrice quantity and, to a lesser extent, the duration of brushing, can elevate oral fluoride post-brushing. Evidence is accumulating that the importance of these variables to fluoride efficacy may have been underestimated.