title: Prevention of tea-induced extrinsic tooth stain.
abstract: OBJECTIVE
  The objectives of this study were to determine whether the addition of milk to tea reduces the ability of tea to stain extracted human teeth and, if so, to ascertain the component of milk that is responsible for milk's stain reducing properties.
  
  
  METHODS
  Extracted human teeth were immersed in a tea solution, with the addition of 2% milk, 5.26% lactose, 2.7% casein or 10% fat-free milk for 24 h at 37°C. A dental spectrophotometer (VITA Easyshade Compact) was used to evaluate the colour of the teeth both before and after immersion in the tea solutions. Commission internationale de l'éclairage (CIE) L*a*b* colour space values were recorded, and the change in colour (ΔE*) was calculated. A two-tailed t-test or one-way analysis of variance (anova) was used to determine whether there were statistical differences between groups.
  
  
  RESULTS
  Milk significantly reduces the ability of tea to stain teeth (P = 0.0225), specifically in the L* and a* dimensions (P = 0.0182 and P = 0.0124, respectively) of the colour sphere. Casein, which makes up 80% of the protein content in bovine milk, is the component of milk that is responsible for significantly reducing tea's ability to stain teeth (P < 0.0001).
  
  
  CONCLUSIONS
  The addition of milk to tea significantly reduces the tea's ability to stain teeth. Casein was determined to be the component of milk that is responsible for preventing tea-induced staining of teeth to a similar order of magnitude that can be obtained by vital bleaching treatments.
authors.affiliation: Faculty of Medicine and Dentistry, School of Dentistry, University of Alberta, Edmonton, AB, Canada.
authors.forename: R J
authors.initials: RJ
authors.lastname: Lee
authors.forename: A
authors.initials: A
authors.lastname: Bayne
authors.forename: M
authors.initials: M
authors.lastname: Tiangco
authors.forename: G
authors.initials: G
authors.lastname: Garen
authors.forename: A K
authors.initials: AK
authors.lastname: Chow
mesh_terms: D000818:Animals; D002364:Caseins / Q000494:pharmacology; D002417:Cattle; D003116:Color; D006801:Humans; D007785:Lactose / Q000494:pharmacology; D008892:Milk / Q000737:chemistry; D013053:Spectrophotometry / Q000295:instrumentation; D013662:Tea / Q000737:chemistry; D013696:Temperature; D013997:Time Factors; D014075:Tooth Discoloration / Q000517:prevention & control*
chemical_list: D002364:Caseins; D013662:Tea; D007785:Lactose
keywords: dental hygiene; diet; extrinsic stain; staining; tooth discoloration