title: Effects of carbamide peroxides on wear resistance and color change of enamel opposing porcelain.
abstract: OBJECTIVE
  This study evaluated the effects of a simulated 1- and 2-week night guard bleaching technique using various bleaching gel concentrations on wear resistance and color change of human enamel opposing a feldspathic porcelain substrate.
  
  
  METHODS
  VMK 68 feldspathic porcelain was formed into 15-mm disks (n = 63) and fired according to manufacturer's recommendations. Enamel cusps were formed and shaped from extracted third molars and treated with 1 of 3 bleaching materials for 7 or 14 days. Specimens were kept at 37 degrees C in 100% humidity. The control group was subjected to identical conditions but with water replacing the bleaching gel between and during bleaching treatments. After simulated bleaching, the enamel cusp specimens were subjected to 3-body wear testing opposite a highly polished porcelain substrate. Enamel wear was evaluated using optical scanning methods, and color was measured with a small-aperture colorimeter. Data were subjected to a one-way repeated- measure analysis of variance and various post hoc statistics.
  
  
  RESULTS
  Results indicated that the within effect of treatment time (7 or 14 days) did not significantly affect (p = 0.13) the size of the resulting enamel wear facet, whereas the between effect of bleaching concentration was significant (p = 0.01). Statistical analysis of unbleached control groups suggests that between-group differences can be explained by variations in wear rates of the 3 enamel groups, not by the concentration differences in bleaching gels. All bleaching treatments resulted in significant color changes (p = 0.04) compared to the unbleached control, but the bleach concentration did not significantly influence the magnitude of color change (p = 0.81).
  
  
  CONCLUSIONS
  A simulated night guard vital bleaching treatment of 1 or 2 weeks had no significant effect on the wear resistance of human enamel in vitro. The increased bleaching treatment time and concentration did not significantly affect the amount of enamel color change.
authors.affiliation: Ohio State University College of Dentistry, Columbus, OH 43218-2357,USA. clelland.l@osu.edu
authors.forename: Nancy L
authors.initials: NL
authors.lastname: Clelland
authors.forename: Yassamin
authors.initials: Y
authors.lastname: Dorosti
authors.forename: Robert R
authors.initials: RR
authors.lastname: Seghi
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry; D000704:Analysis of Variance; D000077463:Carbamide Peroxide; D003116:Color; D003124:Colorimetry; D003743:Dental Enamel / Q000033:anatomy & histology / Q000187:drug effects*; D003776:Dental Porcelain / Q000737:chemistry; D004338:Drug Combinations; D006244:Hardness; D006801:Humans; D006813:Humidity; D016877:Oxidants / Q000008:administration & dosage / Q000627:therapeutic use*; D010545:Peroxides / Q000008:administration & dosage / Q000627:therapeutic use*; D017680:Potassium Compounds / Q000737:chemistry; D013223:Statistics as Topic; D013696:Temperature; D013997:Time Factors; D014073:Tooth Bleaching / Q000295:instrumentation / Q000379:methods; D014508:Urea / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000627:therapeutic use*; D014867:Water / Q000737:chemistry
chemical_list: D000538:Aluminum Silicates; D004338:Drug Combinations; D016877:Oxidants; D010545:Peroxides; D017680:Potassium Compounds; C111131:VMK 68; D014867:Water; D003776:Dental Porcelain; C016447:feldspar; D000077463:Carbamide Peroxide; D014508:Urea