title: An in vitro investigation of two currently marketed dentin tubule occlusion dentifrices.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: GlaxoSmithKline Consumer Healthcare, Weybridge, Surrey, UK. Charles.X.Parkinson@gsk.com
authors.forename: Charles R
authors.initials: CR
authors.lastname: Parkinson
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Willson
mesh_terms: D000085:Acetates / Q000008:administration & dosage / Q000494:pharmacology; D000143:Acids; D000818:Animals; D001120:Arginine / Q000008:administration & dosage / Q000494:pharmacology; D001628:Beverages; D002417:Cattle; D019343:Citric Acid / Q000494:pharmacology; D002957:Citrus; D045424:Complex Mixtures / Q000008:administration & dosage / Q000494:pharmacology; D003802:Dentifrices / Q000008:administration & dosage / Q000494:pharmacology*; D003804:Dentin / Q000187:drug effects* / Q000648:ultrastructure; D057133:Dentin Desensitizing Agents / Q000008:administration & dosage / Q000494:pharmacology*; D004338:Drug Combinations; D005459:Fluorides / Q000008:administration & dosage / Q000494:pharmacology; D005638:Fruit; D006863:Hydrogen-Ion Concentration; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D009566:Nitrates / Q000008:administration & dosage / Q000494:pharmacology; D010710:Phosphates / Q000008:administration & dosage / Q000494:pharmacology; D017680:Potassium Compounds / Q000008:administration & dosage / Q000494:pharmacology; D011897:Random Allocation; D012463:Saliva / Q000502:physiology; D013324:Strontium / Q000008:administration & dosage / Q000494:pharmacology; D013997:Time Factors; D014099:Toothbrushing / Q000295:instrumentation; D014867:Water / Q000737:chemistry
chemical_list: D000085:Acetates; D000143:Acids; D045424:Complex Mixtures; D003802:Dentifrices; D057133:Dentin Desensitizing Agents; D004338:Drug Combinations; D009566:Nitrates; D010710:Phosphates; D017680:Potassium Compounds; C097427:Sensodyne; C444700:colgate sensitive; D014867:Water; D019343:Citric Acid; C106741:strontium acetate; D001120:Arginine; D005459:Fluorides; D013324:Strontium