Microhardness evaluation of in situ vital bleaching and thickening agents on human dental enamel.

Bleaching systems and thickening agents lead to changes in the tooth enamel matrix as a result of an unspecific oxidation of the bleaching gel in the enamel. This reaction may result in a loss of mineral content and a decrease in microhardness. The aim of this study was to evaluate the effects of different bleaching systems and their thickening agents on the microhardness of human enamel in situ. Two dental slabs (3 x 3 x 2 mm) obtained from third molars were fixed on the buccal facial aspects of the maxillary first molars in a group of 45 volunteers. The volunteers were treated with 10% carbamide peroxide gel with carbopol as the thickening agent (group 1), 2% carbopol gel (group 2), 10% carbamide peroxide paste with poloxamer as the thickening agent (group 3), poloxamer (group 4), or 6.5% hydrogen peroxide strips for 21 days (group 5) (experimental treatment factor). The effects of the experimental treatment were evaluated by microhardness tests performed both before and after treatment (time factor). Data were submitted to split-plot analysis of variance and Tukey tests. Only time showed a statistically significant difference (P < .0001). All treatments reduced the enamel microhardness during treatment. Clinically, a reduction in microhardness can be expected after dental bleaching.

Efeito do carbopol como agente espessante sobre a rugosidade superficial do esmalte na técnica de clareamento dental caseiro / Effect of the thickener agent carbopol on dental enamel surface in the at-home dental bleaching

O objetivo deste estudo foi avaliar in vitro o efeito do clareamento caseiro sobre a rugosidade superficial do esmalte dental, utilizando agentes clareadores com e sem o carbopol e o efeito do tratamento com o agente espessante carbopol. Fragmentos de esmalte dental bovino com 3 x 3 mm foram obtidos, incluídos em resina de poliestireno e receberam polimento seqüencial. Em seguida, foram divididos aleatoriamente em 4 grupos, de acordo com o tratamento clareador: G1: peróxido de carbamida 10% com carbopol, G2: peróxido de carbamida 10% sem carbopol, G3: carbowax, e G4: carbopol. O tratamento clareador foi realizado por 6 horas diárias, permanecendo o restante do período em uma solução remineralizadora durante 4 semanas. Os corpos de prova permaneceram imersos na solução remineralizadora por um período adicional de 2 semanas. O efeito dos tratamentos clareadores sobre o esmalte dental foi comparado através da avaliação de rugosidade superficial com o parâmetro RA antes e após o 14, 28 e 42º dias do início do tratamento. A avaliação foi realizada por modelo de análise de variância, sendo em seguida utilizado o teste de Tukey. Após 28 dias de tratamento, todos os produtos testados diminuíram a rugosidade superficial do esmalte dental, permanecendo assim até 14 dias depois do término do tratamento.

The aim of this study was to evaluate in vitro the effect of the at-home dental bleaching on the enamel surface roughness after the use of bleaching agents with and without carbopol and the treatment with the thickner carbopol. Dental bovine slabs with 3 x 3 mm were obtained, embedded in polystyrene resin, and sequentially polished. They were randomized into four groups according to the bleaching treatment: G1: 10% carbamide peroxide with carbopol; G2: 10% carbamide peroxide without carbopol; G3: carbowax; and G4: carbopol. Four weeks of bleaching treatment was performed daily for 6 hours and immersed in artificial saliva for the remaining time. Follow that, the slabs were maintained in artificial saliva for 2 additional weeks. The effect of the bleaching treatments on the dental enamel was compared by surface roughness analyses employing the RA parameter obtained before and after 14th, 28th, and 42nd days of the treatment beginning. The results were statistically analyzed by ANOVA, followed by Tukey’s test. All beaching systems and thickeners agents reduced the enamel surface roughness over 28 days of treatment and also after 14 days after the end of the treatment.