Effect of fluoride therapies on the surface roughness of human enamel exposed to bleaching agents.

OBJECTIVES: To evaluate in vitro the effect of fluoride therapies on the surface roughness of human dental enamel exposed to bleaching agents. METHOD AND MATERIALS: Sixty-six specimens obtained from 33 third molars were centrally cut, mounted on acrylic resin supports, polished, and submitted to baseline surface roughness readings (RaB). Next, the specimens were distributed into 11 groups and exposed to one of the bleaching agents-16% carbamide peroxide (CP) or 35% hydrogen peroxide (HP)-and one of the fluoride therapies-0.05% NaF daily (DF); 0.2% NaF weekly (WF); 2% final topical fluoride (FTF); or 2% initial and final topical fluoride (IFTF). The positive control group specimens were exposed to neither bleaching agents nor fluoride therapies. The negative control group specimens were exposed to the bleaching agents but none of the fluoride therapies. After storage in artificial saliva for 7 days, final surface roughness readings (RaF) were taken. Percentage differences between RaB and RaF were analyzed by ANOVA and Tukey HSD tests at a P value of .05. RESULTS: The bleaching agents CP and HP increased the surface roughness compared with the control group; FTF and IFTF reduced the surface roughness of enamel exposed to CP and HP; DF and WF did not reduce the surface roughness of enamel exposed to CP and HP. CONCLUSION: Both bleaching agents tested increased the surface roughness of dental enamel, and both topical fluoride therapies were effective at reducing the increase in enamel surface roughness after bleaching.

Effects of irradiance, wavelength, and thermal emission of different light curing units on the Knoop and Vickers hardness of a composite resin.

The aim of this study was to evaluate the effects of irradiance, light emission wavelength, and heating of different light curing units on the Knoop and Vickers hardness of a hybrid composite resin. The specimens were irradiated during 40 s with ten different light curing units, LEDs, and halogen lights. The spectral emission of each light curing unit was assessed by a spectrometer, the irradiance was measured by two commercial radiometers, and the heating measured with a thermocouple. After 48 h of storage in a dark recipient under a 100% humidity condition, the Knoop and Vickers hardness tests were carried out. The hardness results were analyzed by ANOVA, and Tukey HSD test (p < 0.05). The results showed that the surface hardness of the composite resin depends not only on the irradiance, but strongly on the emission wavelength and heating of the light curing units. It was observed, a linear correlation between the conversion degree and radiant exposure. In addition, it is suggested that the well known base to top surface hardness ratio convention of 80-90% is not appropriate to evaluate curing efficiency of composites, since the top surface is not always sufficiently polymerized.

Specific concentration evaluation of 16% carbamide peroxide compounded at dispensing pharmacies.

The aim of this work was to evaluate the concentration of carbamide peroxide compounded at different dispensing pharmacies. Immediate concentration analysis was made of bleaching gels dispensed by specialized pharmacies, and of a commercially available gel (control group) (n=20). The carbamide peroxide concentration was determined by titration and the results were analyzed statistically by the Kruskal-Wallis test. The commercial bleaching agent (control group) and one of the gels from the pharmacies presented the best mean concentration values, close to 16%. In conclusion, the concentration of the manipulated and industrialized carbamide peroxide gels presented concentration values differing from 16%.

Specific concentration evaluation of 16 percent carbamide peroxide compounded at dispensing pharmacies

The aim of this work was to evaluate the concentration of carbamide peroxide compounded at different dispensing pharmacies. Immediate concentration analysis was made of bleaching gels dispensed by specialized pharmacies, and of a commercially available gel (control group) (n = 20). The carbamide peroxide concentration was determined by titration and the results were analyzed statistically by the Kruskal-Wallis test. The commercial bleaching agent (control group) and one of the gels from the pharmacies presented the best mean concentration values, close to 16 percent. In conclusion, the concentration of the manipulated and industrialized carbamide peroxide gels presented concentration values differing from 16 percent.

O objetivo deste trabalho foi avaliar a concentração do peróxido de carbamida manipulado em diferentes farmácias de manipulação. Foram utilizados géis clareadores manipulados em farmácias especializadas e um industrializado (grupo controle) (n = 20) com análise de concentração imediata. A concentração do peróxido de carbamida foi obtida por titulometria e os resultados foram submetidos a análise estatística pelo teste de Kruskal-Wallis. Como resultado, o agente clareador (controle) e um dos produtos manipulados em farmácia apresentaram as melhores médias de concentração, próximas a 16 por cento. Pode-se concluir que a concentração do peróxido de carbamida manipulado e dos industrializados apresentaram valores de concentração diferentes de 16 por cento.