title: Development of an acid challenge-based in vitro dentin disc occlusion model.
abstract: OBJECTIVE
  The objective of this study was to evaluate the utility of a novel acid challenge-based dentin disc occlusion model, and to compare the occluding effect and acid resistance exhibited by currently marketed occlusion dentifrices in vitro.
  
  
  METHODS
  Ninety-six bovine dentin discs were polished and etched in citric acid (6% w/w) for two minutes to provide a smooth dentin surface with patent tubules. The discs were divided into three treatment groups. Each treatment group was brushed (Oral-B Vitality Precision Clean/EB 17 FlexiSoft head) twice a day, for up to four days, with either a strontium acetate dentifrice (Sensodyne Rapid Relief), an arginine-based dentifrice (Colgate Sensitive Pro-Relief), or water. Prior to and between treatments, the dentin samples were stored in human saliva. On days 3 and 4, following dentifrice treatment and incubation in saliva (60 minutes), the samples were subjected to a grapefruit juice challenge. Eight samples from each treatment group were removed from the study on each day and analyzed by scanning electron microscopy (SEM). The SEM images were graded according to a categorical occlusion scale, and the data were analyzed by ANOVA.
  
  
  RESULTS
  The strontium acetate dentifrice occluded dentin tubules significantly better than the negative control (water) on days 1 through 4 (day 4 p < or = 0.0001). The marketed occlusion-based dentifrices demonstrated various degrees of dentin tubule occlusion over the four days. The strontium acetate dentifrice demonstrated significantly better occlusion than a currently marketed arginine-based occlusion dentifrice on day 1 (p = 0.0337), day 2 (p = 0.0021 ), and day 4 (p < or = 0.0001).
  
  
  CONCLUSIONS
  An in vitro model has been developed that can differentiate the dentin tubular occlusive effects of currently marketed occlusion dentifrices. Surface analysis reveals that the occluding deposits vary according to product, and that some are more susceptible to acid mediated dissolution.
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: Andrew
authors.initials: A
authors.lastname: Butler
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Willson
mesh_terms: D000085:Acetates / Q000627:therapeutic use; D000134:Acid Etching, Dental; D000818:Animals; D001120:Arginine / Q000627:therapeutic use; D001628:Beverages; D002417:Cattle; D019343:Citric Acid / Q000008:administration & dosage; D032083:Citrus paradisi; D003802:Dentifrices / Q000627:therapeutic use*; D003804:Dentin / Q000187:drug effects* / Q000648:ultrastructure; D057133:Dentin Desensitizing Agents / Q000627:therapeutic use*; D003807:Dentin Sensitivity / Q000188:drug therapy* / Q000473:pathology; D003808:Dentin Solubility / Q000187:drug effects; D006801:Humans; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D011897:Random Allocation; D012463:Saliva / Q000502:physiology; D013324:Strontium / Q000627:therapeutic use; D013997:Time Factors; D014099:Toothbrushing / Q000295:instrumentation
chemical_list: D000085:Acetates; D003802:Dentifrices; D057133:Dentin Desensitizing Agents; D019343:Citric Acid; C106741:strontium acetate; D001120:Arginine; D013324:Strontium