The influence of two home-applied bleaching agents on enamel microhardness: an in situ study.
OBJECTIVE
This in situ study evaluated the influence of two home-applied bleaching agents (10% carbamide peroxide and 7.5% hydrogen peroxide) on enamel microhardness.


METHODS
Ninety enamel slabs were obtained from human third molars and baseline Knoop hardness measurements were recorded under a 50 g load for 5s. The specimens were attached to intra-oral devices delivered to 10 volunteers (donor of the teeth) who used the devices 24h/day throughout the experiment. The specimens were divided in three groups, two experimental and one control; in the last group, enamel slabs were not submitted to bleaching agents, but exposed only to the action of saliva. Two custom-made trays were made for each volunteer to recover the teeth and the appliances containing the enamel slabs. The bleaching regimen was 1h/day for 21 consecutive days. Subsequently, additional hardness measurements were recorded.


RESULTS
The mean values of the baseline and final microhardness were: 348 and 352.2; 346.6 and 354.5; 342 and 340.8, for control, 10% carbamide peroxide and 7.5% hydrogen peroxide groups, respectively. One-way ANOVA of the microhardness mean values revealed no statistically significant differences among groups, the specimens treated with 7.5% hydrogen peroxide has shown a tendency (p=0.056) to microhardness decrease.


CONCLUSIONS
Data suggested that the tested home bleaching agents did not change the superficial enamel microhardness.
Paulista University - UNIP, Brasília, DF, Brazil. elamaia@uol.com.br
Elaine
E
Maia
Luiz Narciso
LN
Baratieri
Mauro Amaral
MA
Caldeira de Andrada
Sylvio
S
Monteiro
Luiz Clóvis Cardoso
LC
Vieira
D000328:Adult; D000704:Analysis of Variance; D000077463:Carbamide Peroxide; D016022:Case-Control Studies; D003743:Dental Enamel / Q000737:chemistry / Q000187:drug effects*; D004338:Drug Combinations; D005260:Female; D006244:Hardness / Q000187:drug effects; D006801:Humans; D006861:Hydrogen Peroxide / Q000009:adverse effects / Q000494:pharmacology*; D008297:Male; D016877:Oxidants / Q000009:adverse effects / Q000494:pharmacology*; D010545:Peroxides / Q000009:adverse effects / Q000494:pharmacology*; D014073:Tooth Bleaching / Q000379:methods*; D014508:Urea / Q000009:adverse effects / Q000031:analogs & derivatives* / Q000494:pharmacology
D004338:Drug Combinations; D016877:Oxidants; D010545:Peroxides; D000077463:Carbamide Peroxide; D014508:Urea; D006861:Hydrogen Peroxide