Susceptibility of bleached enamel and root dentin to artificially formed caries-like lesions.
OBJECTIVE
To evaluate in vitro the susceptibility of caries-like lesion formation on enamel and root dentin that had been bleached with carbamide peroxide agents.


METHODS
150 slabs of bovine enamel and root dentin were ground flat and polished. According to a randomized complete block design, the specimens were then allocated to be bleached with agents (Rembrandt) containing 12% [CP12], 16% [CP16], 22% [CP22] or 30% [CP30] of carbamide peroxide over 21 days. The control group remained unbleached. Afterwards, all specimens were randomly distributed between two subgroups (n= 15): one was subjected to alternating demineralizing and remineralizing solutions to induce caries-like lesions and the other was not. Enamel specimens were cycled four times in demineralizing (pH 5.0) and remineralizing solutions (pH 7.0), while root dentin specimens were cycled twice. Microhardness measurements were carried out at the post-bleaching and at the post-caries lesion formation phases.


RESULTS
In the post-bleaching condition, microhardness values for both enamel and root dentin were dependent on the bleaching agent used. At the post-caries formation stage, there was a significant interaction between the bleaching treatment and substrate condition (carious or noncarious) for enamel and root dentin. Regardless of the bleaching agent, carious enamel and root dentin presented significantly lower microhardness values as compared to the noncarious counterparts. For carious enamel, those specimens exposed to CP16 exhibited higher microhardness values than the subset group formed by CP22, CP30 and unbleached samples. Both subsets did not differ from CP12. For carious root dentin, no difference was observed among the microhardness values attained as a result of the different bleaching treatments.
Department of Restorative Dentistry, Faculdade de Odontologia de Ribeirão Preto - USP, Av. do Cafd, s/n Monte Alegre, SP, Brazil.
Márcio
M
de Menezes
Cecilia Pedroso
CP
Turssi
Juliana Jendiroba
JJ
Faraoni-Romano
Mônica Campos
MC
Serra
D000818:Animals; D000077463:Carbamide Peroxide; D002417:Cattle; D003731:Dental Caries / Q000139:chemically induced*; D003743:Dental Enamel / Q000737:chemistry / Q000187:drug effects; D003804:Dentin / Q000737:chemistry / Q000187:drug effects; D004338:Drug Combinations; D006244:Hardness; D016877:Oxidants / Q000009:adverse effects; D010545:Peroxides / Q000009:adverse effects; D014073:Tooth Bleaching / Q000009:adverse effects*; D014092:Tooth Root / Q000737:chemistry / Q000187:drug effects; D014508:Urea / Q000009:adverse effects / Q000031:analogs & derivatives
D004338:Drug Combinations; D016877:Oxidants; D010545:Peroxides; D000077463:Carbamide Peroxide; D014508:Urea