Comparison of the effects on dentin permeability of two commercially available sensitivity relief dentifrices.

Objective: The in vitro effects of two commercial sensitivity relief dentifrices, one containing 8.0% arginine, calcium carbonate, and 1450 ppm fluoride as sodium monofluorophosphate (MFP), and the other containing 8% strontium acetate and 1040 ppm fluoride as sodium fluoride, in occluding dentin tubules and reducing dentin fluid flow were compared in a blinded study using hydraulic conductance (Flodec).

Methods: Human dentin segments were cut from extracted molars, mounted on acrylic blocks, etched, and connected to a Flodec to measure hydraulic conductance. Segments were divided into two groups (n = 6) and treated for one minute with either the arginine/calcium carbonate dentifrice or the strontium acetate dentifrice. The blocks were rinsed, connected to the Flodec, and the conductance was measured. Blocks were rinsed again and incubated in phosphate-buffered saline (PBS) for at least two hours before the next treatment. The cycle was repeated for a total of three treatments (one using a fingertip and the next two using a toothbrush). After the third treatment, the blocks were incubated in PBS overnight and conductance was re-measured. The two groups were further divided into three sets of two segments each, which were challenged for one minute with either 6% citric acid, orange juice, or grapefruit juice.

Results: The hydraulic conductance study showed that the dentifrice containing 8.0% arginine, calcium carbonate, and 1450 ppm fluoride provided a significantly higher percentage reduction in fluid flow immediately after fingertip application, as well as after two brushing cycles, compared to the dentifrice containing 8% strontium acetate and 1040 ppm fluoride. After various acid challenges, the percentage reduction in fluid flow of dentin treated with the arginine/calcium carbonate dentifrice remained significantly higher than that of the strontium acetate dentifrice. These results are highly consistent with the results from an independent clinical study which showed that the arginine/calcium carbonate dentifrice provided dentin hypersensitivity relief immediately after direct topical application with a fingertip and massage for one minute per sensitive tooth, whereas the strontium acetate dentifrice did not.

Conclusion: Based on this in vitro hydraulic conductance study, the dentifrice containing 8.0% arginine, calcium carbonate, and 1450 ppm fluoride was significantly more effective in reducing fluid flow through dentin tubules as a result of occlusion than the dentifrice containing 8% strontium acetate and 1040 ppm fluoride. Further, the superior occlusion obtained with the arginine/calcium carbonate dentifrice was resistant to acid challenge.