Enamel and Dentin Microhardness and Chemical Composition After Experimental Light-activated Bleaching.
OBJECTIVE
To evaluate 1) the influence of five bleaching agents (with additional light activation) on enamel and dentin surface microhardness and chemical composition and 2) the remineralizing potential of artificial saliva and amorphous calcium phosphate (ACP).


METHODS
The study was conducted on 125 human third molars dissected into quarters for separate enamel and dentin measurements. The bleaching process was performed with 38% and 25% hydrogen peroxide (HP) and 30%, 16%, and 10% carbamide peroxide (CP) gels two times for 15 minutes each time. All bleaching gels were tested alone and in combination with ZOOM2, light-emitting diode (LED), organic LED, and femtosecond laser. A total of 25 bleaching combinations (n=10) were evaluated. Microhardness was measured by a Vickers diamond. Chemical analysis was performed using energy-dispersive X-ray spectroscopy.


RESULTS
Bleaching agents used in the absence of light activation caused a significant reduction in enamel and dentin surface microhardness (p<0.001), ranging from 8% for 16% CP to 40% for 25% HP. The effects of different light activations were negligible. After two-week treatment with ACP and artificial saliva, maximum deviation from baseline microhardness was just 3%. Such treatment increased the concentrations of calcium, phosphorus, and fluorine.


CONCLUSIONS
An increase in peroxide concentration and gel acidity negatively affected microhardness and concentrations of calcium and phosphorus in enamel and dentin. ACP and artificial saliva stimulated the remineralization of hard tissues.
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Milat
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D002130:Calcium Phosphates / Q000494:pharmacology*; D000077463:Carbamide Peroxide / Q000494:pharmacology*; D003743:Dental Enamel / Q000737:chemistry / Q000187:drug effects*; D003804:Dentin / Q000737:chemistry / Q000187:drug effects*; D006244:Hardness; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D008027:Light; D008963:Molar; D012464:Saliva, Artificial / Q000494:pharmacology; D013499:Surface Properties; D014073:Tooth Bleaching / Q000009:adverse effects / Q000379:methods; D058205:Tooth Bleaching Agents / Q000494:pharmacology*; D017001:Tooth Demineralization / Q000628:therapy; D014089:Tooth Remineralization / Q000379:methods
D002130:Calcium Phosphates; D012464:Saliva, Artificial; D058205:Tooth Bleaching Agents; C519480:amorphous calcium phosphate; D000077463:Carbamide Peroxide; D006861:Hydrogen Peroxide