ABSTRACT
Aim: The aim of this in vitro study was to evaluate the influence of dye solution on enamel color change after bleaching protocols and the effectiveness in maintaining the color of these agents. Material and Methods: The buccal surfaces of sixty-five bovine incisors were cleaned and polished, and the enamel specimens were divided into thirteen groups: G1 to G6: treated with 6% hydrogen peroxide using different surface agents; G7 to G12: treated with 15% hydrogen peroxide using different surface agents; G13: control. After 24 hours, the groups treated were immersed in black tea solution; the control group was stored in artificial saliva. The color was evaluated prior to bleaching, 24 hours later and after immersion in the dye solution; the roughness was measured immediately after bleaching, 24 hours later and 7 days after immersion in the dye solution. The data was analyzed using the Kruskal-Wallis test, followed by the Miller test for roughness analysis, and the Duncan test for color change analysis. It was used 5% significant level with p<0.05. Results: The data found in the evaluation of surface roughness after bleaching indicated a reduction of roughness in all the groups. The surface agent Bifluoride, when applied, showed an increase in roughness after its application and it decreases after immersion in dye solution; the surface agent Desensibilize and the XP Bond adhesive showed greater color alteration after immersion in dye solution. Conclusions: All the groups studied, under different whitening technique, were effective in promoting whitening.
ABSTRACT
Este estudo in vitro avaliou a influência do tempo de aplicação do bicarbonato de sódio a 10% na qualidade da união de um sistema adesivo universal unido ao esmalte bovino clareado por meio de testes de resistência de união (microtração imediata e após 6 meses) e grau de conversão na interface adesiva (espectroscopia micro-Raman). Cento e dez blocos de esmalte bovino (4x4 mm) foram planificados e distribuídos aleatoriamente em 5 grupos: C: controle, sem clareamento; B: clareamento com peróxido de hidrogênio 35% (HP); BS3: clareamento com HP seguido de tratamento com a solução de bicarbonato de sódio 10% (BS) por 3 min; BS5: clareamento com HP seguido de tratamento com BS por 5 min; BS10: clareamento com HP seguido de tratamento com BS por 10 min. O HP foi aplicado duas vezes (20 minutos cada, com exceção do grupo C) e em seguida as restaurações adesivas foram realizadas. Após 24 horas, 20 espécimes de cada grupo foram seccionados em palitos (1x1 mm) e submetidos ao teste de resistência de união (imediato e após 6 meses) em máquina de ensaios universal com velocidade de 0,5 mm/min (n=10). Os dados foram analisados por ANOVA a dois critérios (p <0,05). As médias das análises imediata e após 6 meses foram: C: 26,77 / 25,32; B: 26,42 / 26,42; BS3: 23,95 / 22,98; BS5: 23,65 / 26,64; BS10: 23,42 / 29,30. Nenhum dos fatores testados apresentou significância: tratamento (p=0,349) e tempo (p=0,234), não havendo interação entre estes (p=0,198). Falhas adesivas foram predominantes nos dois períodos de avaliação. Para a análise do grau de conversão, após 24 horas da restauração, 2 espécimes de cada grupo foram seccionados em fatias de 1mm, sendo apenas 3 fatias selecionadas. Os seguintes parâmetros foram utilizados: excitação dos espécimes com laser de argônio operando a 538 nm, espectro obtido a uma resolução ~4cm-1, sob uma região de espectro entre 1580-1660cm-1, verificando a altura dos picos 1608cm-1 e 1637cm-1. Os dados foram analisados por ANOVA a um critério (p <0,05) e as médias do grau de conversão foram: C: 71,10%; B: 72,11%; BS3: 73,98%; BS5: 69,25%; BS10: 70,56%. O fator de estudo tratamento não apresentou significância estatística (p=0,808). A adesão no esmalte clareado parece não ter sido afetada negativamente quando restaurações adesivas foram feitas imediatamente após o clareamento, independente da aplicação ou não da substância antioxidante. Mais estudos que avaliem a adesão em esmalte clareado, principalmente no que diz respeito ao grau de conversão e aos diferentes tipos de sistemas adesivos universais se fazem necessários para fins comparativos e para que possamos indicar seguramente as restaurações imediatas (quando necessárias) na prática clínica.(AU)
The present in vitro study evaluated the influence of the application time of 10% sodium bicarbonate in the adhesion quality of a universal adhesive system bonded to bleached enamel through microtensile bond strength testing (immediate and after 6 months) and the degree conversion (micro-Raman spectroscopy). One hundred and ten bovine enamel blocks (4x4mm) were flattened and randomly allocated into 5 groups: C: control, without bleaching; B: bleached with 35% hydrogen peroxide (HP); BS3: bleached and treated with 10% sodium bicarbonate solution (BS) for 3 min; BS5: bleached and treated with BS for 5 min; BS10: bleached and treated with BS for 10 min. HP was applied twice (20 minutes each, except in group C) and the adhesive restorations were performed. After 24 hours, 20 specimens from each group were sectioned into sticks (1x1 mm) and submitted to microtensile bond strength testing (immediately and after 6 months) in a universal testing machine with a crosshead speed of 0.5 mm/min (n = 10). Data was analyzed by two-way ANOVA (p <0.05). The means of the immediate and 6 months analysis were: C 26.77 / 25.32; B: 26.42 / 26.42; BS3: 23.95 / 22.98; BS5: 23.65 / 26.64; BS10: 23.42 / 29.30. None of the tested factors showed significance: treatment (p = 0.349) and time (p = 0.234), with no interaction between them (p = 0.198). Adhesive failures were predominant in both evaluation periods. For the degree of conversion analysis, 2 specimens of each group were sectioned into 1 mm slices after 24 hours of the restorative procedure, and 3 slices were selected. The following parameters were used: excitation of specimens with argon laser operating at 538 nm, spectrum obtained at a resolution of ~4cm-1, under a spectrum region between 1580-1660cm-1, evaluating the height of the peaks at 1608cm-1 and 1637cm-1. Data was analyzed by one-way ANOVA (p <0.05). The means of degree of conversion were: C: 71.10%; B: 72.11%; BS3: 73.98%; BS5: 69.25%; BS10: 70.56%. The study factor "treatment" was not statistically significant (p = 0.808). The results of bonding to bleached enamel was not negatively affected when adhesive restorations were made immediately after bleaching, regardless of the application of the antioxidant substance. Further studies to evaluate the adhesion on bleached enamel, mainly with regard to the degree of conversion and different types of universal adhesive systems are needed for comparative purposes. Only after this, the immediate restoration (if necessary) in clinical practice can be safely and indicated.(AU)