Abstract
Dental bleaching occurs due to an oxidation reaction between the bleaching agents and the macromolecules of pigments in the teeth. This reaction is unspecific and the peroxides can also affect the dental matrix causing mineral loss. On the other hand, recent studies have suggested that the thickener agent carbopol can also cause mineral loss. Thus, the objective of this study was to evaluate in vitro the effect of at-home dental bleaching on dental enamel microhardness after the use of bleaching agents with and without carbopol as a thickener agent. Bovine dental slabs with 3 x 3 x 3 mm were obtained, sequentially polished, and randomly divided into 4 groups according to the experimental treatment: G1: 2% carbopol; G2: 10% carbamide peroxide with carbopol; G3: carbowax; G4: 10% carbamide peroxide with poloxamer. Bleaching was performed daily for 4 weeks, immersed in artificial saliva. Enamel microhardness values were obtained before the treatment (T0) and 7 (T1), 14 (T2), 21 (T3), 28 (T4), and 42 (T5) days after the beginning of the treatment. ANOVA and Tukey's test revealed statistically significant differences only for the factor Time (F = 5.48; p < 0.01). All bleaching and thickener agents caused no alterations on the enamel microhardness.
Highlights
Discolored teeth are considered a major problem by society and they are incorrectly attributed to diseases.[8]
The mean values of enamel microhardness, before and following the treatments, and the respective standard deviations are shown in Table 2, and the behavior of enamel microhardness may be observed in Graph 1
This study showed that the in vitro use of carbopol or carbowax caused no mineral loss, but further studies should be conducted to assess the effect of thickener agents for longer exposure times and to study other options of thickener agents that may cause less effects on enamel
Summary
Discolored teeth are considered a major problem by society and they are incorrectly attributed to diseases.[8] As a solution for this kind of problem there are many options like crowns, laminated veneers, enamel microabrasion, and dental bleaching.[8] Among these techniques, dental bleaching is the most conservative, easy, and commonly used by clinicians.[8]. At-home bleaching has become one of the most used techniques because of its simplicity, low cost and safety due to the use of low concentrations of peroxide (10% to 16% carbamide peroxide).[8] 10% carbamide peroxide is still currently commonly used, manufacturers have recently begun to introduce higher concentrations of bleaching agents and alternative methods for tooth bleaching to achieve faster results.[8,11]. Teeth are bleached by an oxidation-reduction reaction caused by the decomposition of the hydrogen peroxide into free radicals such as oxygen and perhydroxyl.[8,13] Because of the absence of an electron on the last layer, the oxygen (O) and perhydroxyl (HO2) – free radicals – are extremely electrophilic and diffuse throughout enamel and dentin matrix to attack the macromolecules of pigments (organic molecules) and acquire stability.[7,8] the intrinsic pigments composed by highly unsaturated organic macromolecules are transformed into less complex molecules, which are smaller, simpler and lighter than the original ones.[8]
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