title: Effect of hydrogen peroxide on intertubular dentine.
abstract: OBJECTIVE
  To evaluate the effect of 30% hydrogen peroxide on the surface changes and nanomechanical properties of intertubular dentine.
  
  
  METHODS
  Five freshly extracted human premolars were sectioned and two specimens were obtained from each tooth. Atomic force microscopy (AFM) images of dentine were taken. Baseline hardness and Young's modulus of intertubular dentine were determined using nanoindentation testing and recorded. The specimens were then treated with either 0.5 ml of Hank's balanced salt solution (control group) or 30% hydrogen peroxide at 24 degrees C for 24 h. AFM imaging and determination of hardness and Young's modulus of intertubular dentine were then repeated. The images were compared and statistical analyses of hardness and Young's modulus were carried out using paired sample t-tests.
  
  
  RESULTS
  The AFM images showed recession of the intertubular dentine surface post-bleaching. For the control group, there was no significant change in hardness (p=0.124) and Young's modulus (p=0.438) of intertubular dentine. However, a significant decrease in hardness (p=0.002) and Young's modulus (p=0.001) of intertubular dentine was observed for the experimental group.
  
  
  CONCLUSIONS
  Exposure to 30% hydrogen peroxide for 24 h caused surface changes to intertubular dentine and significantly decreased the hardness and Young's modulus of intertubular dentine.
authors.affiliation: Department of Restorative Dentistry, Faculty of Dentistry, National University of Singapore, 5 Lower Kent Ridge Road, Singapore 119074, Singapore. rsdchk@nus.edu.sg
authors.forename: H K
authors.initials: HK
authors.lastname: Chng
authors.forename: H N
authors.initials: HN
authors.lastname: Ramli
authors.forename: A U J
authors.initials: AU
authors.lastname: Yap
authors.forename: C T
authors.initials: CT
authors.lastname: Lim
mesh_terms: D003804:Dentin / Q000187:drug effects* / Q000648:ultrastructure; D004548:Elasticity / Q000187:drug effects; D006244:Hardness / Q000187:drug effects; D006801:Humans; D006861:Hydrogen Peroxide / Q000633:toxicity*; D018625:Microscopy, Atomic Force; D016877:Oxidants / Q000633:toxicity*; D014073:Tooth Bleaching / Q000009:adverse effects*
chemical_list: D016877:Oxidants; D006861:Hydrogen Peroxide