title: Ultrastructural changes in the cemento-enamel junction after vital tooth bleaching with fluoride and fluoride-free agents - a pilot study.
abstract: BACKGROUND
  The impact of bleaching on the cemento-enamel junction (CEJ) is not well known. Due to frequent sensitivity of the cervical region of teeth after the vital bleaching, the aim of the present study was to evaluate the morphological features of the CEJ of human teeth after application of fluoridated and fluoride-free bleaching agents, as well as post-bleaching fluoridation treatment, by scanning electron microscopy (SEM) analysis.
  
  
  METHODS
  Thirty-five extracted permanent human teeth were longitudinally cut, yielding 70 specimens. Thirty specimens were randomly divided into the 3 experimental groups, and 20 specimens, were used as (2) control groups, each: negative (untreated) control group; positive control group treated with 35% hydrogen peroxide; experimental group 1, bleaching with 10% carbamide peroxide (CP); experimental group 2, treatment with a mixture of 10% CP and fluoride; and experimental group 3, treatment with 10% CP and 2% sodium fluoride gel applied 30 minutes after bleaching. Experimental groups were treated 8 h per day for 14 days. The samples were examined by SEM.
  
  
  RESULTS
  The bleaching materials tested caused morphological changes to the surface of the CEJ. There was a statistically significant difference between experimental groups (Kruskal Wallis Test chi-square=11,668; p<0.005). Mean value of experimental group 2 scores showed statistically significant difference from groups 1 and 3.
  
  
  CONCLUSIONS
  Bleaching gel with fluorides does not significantly change morphological appearance of the CEJ and represents a better choice than the hard tissue fluoridation process after bleaching.
authors.affiliation: Department of Restorative Dentistry and Endodontics, Clinic of Dentistry, Medical Faculty, University of Nis, Nis, Serbia. jgasic@yahoo.com
authors.forename: Jovanka
authors.initials: J
authors.lastname: Gasic
authors.forename: Ljiljana
authors.initials: L
authors.lastname: Kesic
authors.forename: Jelena
authors.initials: J
authors.lastname: Popovic
authors.forename: Aleksandar
authors.initials: A
authors.lastname: Mitić
authors.forename: Marija
authors.initials: M
authors.lastname: Nikolic
authors.forename: Sasa
authors.initials: S
authors.lastname: Stankovic
authors.forename: Radomir
authors.initials: R
authors.lastname: Barac
mesh_terms: D005459:Fluorides / Q000008:administration & dosage*; D006801:Humans; D006861:Hydrogen Peroxide / Q000008:administration & dosage*; D008855:Microscopy, Electron, Scanning; D010865:Pilot Projects; D014073:Tooth Bleaching; D019237:Tooth Cervix / Q000648:ultrastructure*
chemical_list: D006861:Hydrogen Peroxide; D005459:Fluorides