title: Graded changes in enamel component volumes resulted from a short tooth bleaching procedure.
abstract: OBJECTIVE
  To test the hypothesis that changes in enamel component volumes (mineral, organic, and water volumes, and permeability) are graded from outer to inner enamel after a short bleaching procedure.
  
  
  METHODS
  Extracted unerupted human third molars had half of their crowns bleached (single bleaching session, 3 × 15 min), and tooth shade changes in bleached parts were analyzed with a spectrophotometer. Ground sections were prepared, component volumes and permeability were quantified at histological points located at varying distances from the enamel surface (n=10 points/location), representing conditions before and after bleaching.
  
  
  RESULTS
  Tooth shade changes were significant (p<0.001; 95% CI=-1/-8; power=99%), and most of the enamel layer was unaffected after bleaching, except at the outer layers. Multiple analysis of covariances revealed that most of the variance of the change in enamel composition after bleaching was explained by the combination of the set of types of component volume (in decreasing order of relevance: mineral loss, organic gain, water gain, and decrease in permeability) with the set of distances from the enamel surface (graded from the enamel surface inward) (canonical R(2)=0.97; p<0.0001; power>99%).
  
  
  CONCLUSIONS
  Changes in enamel composition after a short bleaching procedure followed a gradient within component volumes (mineral loss>organic gain>water gain>decrease in permeability) and decreased from the enamel surface inward.
authors: Master Program in Dentistry, Health Sciences Center, Federal University of Pernambuco, Av. Prof. Moraes Rego 1235, 50670-901 Recife, Pernambuco, Brazil.
authors: Artemisa Fernanda Moura
authors: AF
authors: Ferreira
authors: Master Program in Dentistry, Health Sciences Center, Federal University of Pernambuco, Av. Prof. Moraes Rego 1235, 50670-901 Recife, Pernambuco, Brazil.
authors: Flávia Maria de Moraes Ramos
authors: FM
authors: Perez
authors: Department of Morphology, Health Science Center, Federal University of Paraiba, Cidade Universitária, 58051-900 João Pessoa, Paraiba, Brazil.
authors: Francisco de Assis
authors: Fde A
authors: Limeira Júnior
authors: Master Program in Dentistry, Health Sciences Center, Federal University of Paraiba, Cidade Universitária, 58051-900 João Pessoa, Paraiba, Brazil.
authors: Mirella de Fátima Liberato
authors: Mde F
authors: de Moura
authors: Master Program in Dentistry, Health Sciences Center, Federal University of Paraiba, Cidade Universitária, 58051-900 João Pessoa, Paraiba, Brazil; Department of Morphology, Health Science Center, Federal University of Paraiba, Cidade Universitária, 58051-900 João Pessoa, Paraiba, Brazil. Electronic address: fredericosousa@hotmail.com.
authors: Frederico Barbosa
authors: FB
authors: de Sousa
mesh_terms: D003743:Dental Enamel / Q000737:chemistry* / Q000166:cytology / Q000187:drug effects*; D006244:Hardness / Q000187:drug effects; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008855:Microscopy, Electron, Scanning; D008859:Microscopy, Polarization; D008903:Minerals / Q000032:analysis; D008964:Molar, Third / Q000187:drug effects; D013053:Spectrophotometry / Q000379:methods; D013499:Surface Properties; D014073:Tooth Bleaching / Q000009:adverse effects* / Q000379:methods; D058205:Tooth Bleaching Agents / Q000494:pharmacology; D017001:Tooth Demineralization; D014088:Tooth Permeability / Q000187:drug effects
chemical_list: D008903:Minerals; D058205:Tooth Bleaching Agents; D006861:Hydrogen Peroxide
keywords: Biochemistry; Enamel; Histology; Hydrogen peroxide; Tooth bleaching