Research Article: Dental enamel bleached for a prolonged and excessive time: Morphological changes

Date Published: April 5, 2019

Publisher: Public Library of Science

Author(s): Kelly Fernanda Barbosa Vilhena, Bárbara Catarina Lima Nogueira, Nathalia Carolina Fernandes Fagundes, Sandro Cordeiro Loretto, Rômulo Simões Angelica, Rafael Rodrigues Lima, Mário Honorato Silva e Souza, Aristides Docoslis.


This work aimed to evaluate the roughness, microhardness, ultrastructure, chemical composition and crystalline structure in submitted teeth to a prolonged home bleaching regimen with 10% carbamide peroxide (10% PC) for different periods. The specimens were divided into the following groups: G1: negative control (application of water-soluble gel); G2: tooth whitening group (positive control), under application time recommended by the manufacturer (4h/14 days); G3: prolonged whitening 50%, under prolonged time recommended by the manufacturer in 50% (4h/21 days); G4: excessive whitening 100%, under exceeded manufacturer recommended time by 100% (4h/ 28 days). The results were evaluated descriptively and analytically. There were no changes in the roughness in any of the evaluated groups. However, the microhardness decreased in the G4 group. Scanning electron microscopy showed changes in the enamel surface of groups G2, G3 and G4. Dispersive X-ray spectroscopy identified changes in the concentration of chemical elements O, Mg, P, K in all groups. Thus, this study showed that prolonged home bleaching could cause changes in the ultrastructure, chemical composition and microhardness of the enamel.

Partial Text

The search for whiter teeth pattern has encouraged the consumption of bleaching agents. Due to this demand, a high diversity of products has been launched, with a portion of these characterized by low-cost sale without a dentist office visit [1]. Possible damages to the oral structure can occur with excessive use of bleaching products such as burns, transient sensitivity, reduction of microhardness and increase of roughness [2,3], information that is usually omitted by the manufacturer or even ignored by the population.

The use of 10% CP gel for an extended period was able to cause changes in the structure and microhardness of the dental enamel, but without changes in the enamel roughness (Table 1). The O, Mg, P, K elements varied in their levels throughout the studied period without modification of the crystalline structure of the enamel.

Finally, the results of this investigation show that the 10% PC bleaching gel, when used in a way that exceeds the time recommended by the manufacturer, was able to reduce the microhardness, modify the ultrastructure and promote variations in the chemical composition of the enamel.




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