An in vitro investigation of two currently marketed dentin tubule occlusion dentifrices

The objective of this study was to evaluate the relative level of dentin tubule occlusion afforded by two dentifrices specifically developed to occlude dentin tubules, following finger-applied dab-on application and by repeated brushing, in a longitudinal acid-challenge-based dentin disk model. The impact of a dietary acid alone (grapefruit juice) on the level of dentin tubule occlusion conferred by each product following dab-on application was also explored in a separate short-term stand-alone exploratory dentin disk-based in vitro study.

For the longitudinal study, 120 bovine dentin discs, polished and etched in citric acid for two minutes to provide a smooth dentin surface with patent tubules, were divided into three treatment groups and subjected to a finger application of the dentifrice only, or a combination of finger application and brushing. Prior to and between treatments, the dentin samples were stored in saliva (for > 60 minutes). The test products were an 8% w/w strontium acetate dentifrice (currently marketed as Sensodyne Rapid Relief), an arginine-based dentifrice (marketed as Colgate Sensitive Pro-Relief), and deionized water. For the exploratory acid resistance study, 24 dentin samples were divided into two treatment groups. Treatment consisted of a single dab-on application with the test dentifrices to the hydrated surface of dentin, followed by exposure to either a 30-second or 10-minute grapefruit juice acid challenge. For both models, at the end of each treatment period, the samples were removed for scanning electron microscopy analysis and graded on a categorical visual scale. All data were analyzed statistically by unpaired t-test comparison.

In the longitudinal (four-day) model, the strontium acetate-based dentifrice occluded dentin tubules significantly better than the currently marketed arginine-based dentifrice post-dab-on treatment and grapefruit juice challenge (p < 0.0001). At all other time points, the strontium acetate dentifrice demonstrated significantly better occlusion than the arginine-based dentifrice (p < or = 0.0001). In the exploratory acid resistance model, the level of occlusion observed for the strontium acetate dentifrice was statistically significantly greater when compared to the arginine dentifrice following 10-second and 10-minute (p < 0.0001) exposures to grapefruit juice.

A strontium acetate dentifrice is observed to deliver statistically significantly greater levels of dentin tubule occlusion when compared to the arginine dentifrice following dab-on and brushing application under dietary acid-challenge conditions in this in vitro model. This study suggests that the arginine-containing dentifrice may be more susceptible to acid-mediated dissolution than the strontium-based dentifrice under the conditions employed in this in vitro model.