title: Effects of tooth whitening and orange juice on surface properties of dental enamel.
abstract: OBJECTIVE
  To study the effects of 6% H2O2 activated with LED light on surface enamel as compared to orange juice challenges in vitro.
  
  
  METHODS
  A total of 40 human enamel discs were incubated in saliva overnight to allow pellicle formation and then divided into three groups: 15 for whitening treatments, 15 for orange juice immersions and 10 for normal saline controls. Baseline microhardness was measured with a microhardness Knoop indenter (50g, 10s) and surface topography was evaluated with a focus-variation 3D scanning microscopy. Enamel discs were treated with H2O2 or orange juice for 20 min each cycle for five cycles to simulate daily treatment with the products for 5 days. The discs were stored in saliva between treatment cycles. Microhardness and surface topography were evaluated again after treatments. Changes in microhardness and in surface area roughness (Sa), mean maximum peak-to-valley distance (Sz) and the developed surface area ratio (Sdr) were compared before and after treatments (t-test) and among groups (ANOVA).
  
  
  RESULTS
  Enamel surface hardness decreased by 84% after orange juice immersion but no statistically significant changes were observed in the whitening and control groups. Surface topography changed significantly only in the orange juice group as shown by increased Sa (1.2 microm vs. 2.0 microm), Sz (7.7 microm vs. 10.2 microm) and Sdr (2.8% vs. 6.0%). No such changes were observed in the whitening and control groups.
  
  
  CONCLUSIONS
  In comparison to orange juice challenges, the effects of 6% H2O2 on surface enamel are insignificant. Orange juice erosion markedly decreased hardness and increased roughness of enamel.
authors.affiliation: University of Rochester Eastman Dental Center, 625 Elmwood Avenue, Rochester, NY 14620, United States. yanfang_ren@urmc.rochester.edu
authors.forename: Yan-Fang
authors.initials: YF
authors.lastname: Ren
authors.forename: Azadeh
authors.initials: A
authors.lastname: Amin
authors.forename: Hans
authors.initials: H
authors.lastname: Malmstrom
mesh_terms: D001628:Beverages; D032084:Citrus sinensis; D003743:Dental Enamel / Q000187:drug effects / Q000473:pathology*; D044622:Dental Pellicle / Q000473:pathology; D006244:Hardness; D006801:Humans; D006861:Hydrogen Peroxide / Q000627:therapeutic use*; D021621:Imaging, Three-Dimensional / Q000379:methods; D008029:Lighting / Q000295:instrumentation; D016877:Oxidants / Q000627:therapeutic use*; D012463:Saliva / Q000502:physiology; D014073:Tooth Bleaching / Q000379:methods*; D014077:Tooth Erosion / Q000209:etiology / Q000473:pathology
chemical_list: D016877:Oxidants; D006861:Hydrogen Peroxide