Effect of tray-based and trayless tooth whitening systems on microhardness of enamel surface and subsurface.
OBJECTIVE
To evaluate the effect of tray-based and trayless tooth whitening systems on surface and subsurface microhardness of human enamel.


METHODS
Enamel slabs were obtained from recently extracted human third molars. Specimens were randomly assigned to six groups according to tooth whitening treatment (n = 10): 6.0% hydrogen peroxide (HP) (Crest Whitestrips), 6.5% HP (Crest Professional Whitestrips), 7.5% HP (Day White Excel 3), 9.5% HP (Day White Excel 3), 10% carbamide peroxide (Opalescence), and a control group (untreated). Specimens were treated for 14 days following manufacturers' recommended protocols, and were immersed in artificial saliva between treatments. Enamel surface Knoop microhardness (KHN) was measured immediately before treatment, and at days 1, 7, and 14 of treatment. After treatment, subsurface microhardness was measured at depths of 50-500 microm. Data were analyzed for statistical significance using analysis of variance.


RESULTS
Differences in microhardness for treated vs. untreated enamel surface were not statistically significant at any time interval. For 6.5% and 9.5% HP, there was a decrease in surface microhardness values during treatment, but at the end of treatment the microhardness values were not statistically different from the baseline values. For the enamel subsurface values, no differences were observed between treated vs. untreated specimens at each depth. Trayless and tray-based tooth whitening treatments do not significantly affect surface or subsurface enamel microhardness.
Teixeira
Erica C N
EC
Department of Operative Dentistry, School of Dentistry, The University of North Carolina at Chapel Hill, 302 Brauer Hall, CB#7450, Chapel Hill, NC 27599-7450, USA. teixeire@dentistry.unc.edu
Ritter
André V
AV
Thompson
Jeffrey Y
JY
Leonard
Ralph H
RH
Swift
Edward J
EJ
D000077463:Carbamide Peroxide; D002985:Clinical Protocols; D003743:Dental Enamel / Q000648:ultrastructure*; D004338:Drug Combinations; D006244:Hardness; D006801:Humans; D006861:Hydrogen Peroxide / Q000008:administration & dosage / Q000627:therapeutic use; D016877:Oxidants / Q000008:administration & dosage / Q000627:therapeutic use; D010545:Peroxides / Q000008:administration & dosage / Q000627:therapeutic use; D012464:Saliva, Artificial / Q000737:chemistry; D013997:Time Factors; D014073:Tooth Bleaching / Q000295:instrumentation* / Q000379:methods; D014508:Urea / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000627:therapeutic use
D004338:Drug Combinations; D016877:Oxidants; D010545:Peroxides; D012464:Saliva, Artificial; D000077463:Carbamide Peroxide; D014508:Urea; D006861:Hydrogen Peroxide