Surface microhardness of enamel after different home bleaching procedures.
OBJECTIVE
The purpose of this study was to evaluate the influence of different home bleaching procedures on surface microhardness of human enamel.


METHODS
Among eight groups 192 incisors were distributed. The facial surface of each incisor was polished and baseline hardness of enamel (m0; Knoop) was assessed with a load of 1N for 30s. Subsequently, the enamel was treated for 14 days with the bleaching agent: groups 1, 2 and 4 Viva Style Paint on, 8% carbamide peroxide (CP) 1x20min, 2x20min and 2x5min; group 3 Colgate Simply White, 5.9% hydrogen peroxide (HP), 2x30min; group 5 Viva Style 10% CP 1x1h; group 6 Blend-a-med White Strips, 5.9% HP 2x30min; group 7 Odol-med3 Beauty-Kur, sodium chlorite 2x10min; group 8 control, running water 1x1h. Hardness was reassessed after the last bleaching treatment (m1) and after 6 weeks storage in artificial saliva (m2).


RESULTS
Changes in microhardness were as follows (m0-m1): (1) -2.3 (+/-20.3); (2) -8.9 (+/-27.2); (3) 63.4 (+/-56.3); (4) 9.6 (+/-30.1); (5) 12.8 (+/-62.6); (6) 92.2 (+/-50.2); (7) 158.4 (+/-59.7); (8) 10.6 (+/-38.5). Statistical analysis showed that hardness values were significantly (p< or =0.0005; Wilcoxon test) reduced in groups 3, 6, and 7 (m1) and in group 7 (m2).


CONCLUSIONS
Both type of bleaching agent and concentration have a significant influence on the microhardness of enamel. The most critical bleaching agent seems to be the one containing sodium chlorite in combination with citric acid.
Zantner
Catharina
C
Department of Operative Dentistry and Periodontology, University School of Dental Medicine, Campus Benjamin Franklin, Charité-Universitätsmedizin Berlin, Berlin, Germany. catharina.zantner@charite.de
Beheim-Schwarzbach
Nils
N
Neumann
Konrad
K
Kielbassa
Andrej M
AM
D000077463:Carbamide Peroxide; D002712:Chlorides / Q000008:administration & dosage / Q000627:therapeutic use; D019343:Citric Acid / Q000008:administration & dosage / Q000627:therapeutic use; D045424:Complex Mixtures / Q000008:administration & dosage / Q000627:therapeutic use; D003743:Dental Enamel / Q000187:drug effects* / Q000473:pathology; D004338:Drug Combinations; D005782:Gels; D006244:Hardness; D006801:Humans; D006861:Hydrogen Peroxide / Q000008:administration & dosage / Q000627:therapeutic use; D006863:Hydrogen-Ion Concentration; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D016877:Oxidants / Q000008:administration & dosage / Q000627:therapeutic use*; D010545:Peroxides / Q000008:administration & dosage / Q000627:therapeutic use; D012464:Saliva, Artificial / Q000008:administration & dosage; D013314:Stress, Mechanical; D014073:Tooth Bleaching / Q000379:methods*; D014508:Urea / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000627:therapeutic use; D014867:Water / Q000008:administration & dosage
D002712:Chlorides; C475021:Colgate Simply White Clear Whitening Gel; D045424:Complex Mixtures; D004338:Drug Combinations; D005782:Gels; D016877:Oxidants; D010545:Peroxides; D012464:Saliva, Artificial; C500417:Vivastyle; D014867:Water; D019343:Citric Acid; D000077463:Carbamide Peroxide; D014508:Urea; D006861:Hydrogen Peroxide; C001599:chlorite