Influence of concentration and activation on hydrogen peroxide diffusion through dental tissues in vitro.

This study evaluated the effect of physical and chemical activation on the diffusion time of different concentrations of hydrogen peroxide (HP) bleaching agents through enamel and dentin. One hundred and twenty bovine cylindrical specimens were divided into six groups (n = 20): 20% HP; 20% HP with light activation; 20% HP with manganese gluconate; 35% HP; 35% HP with light activation; and 35% HP with manganese gluconate. The specimens were fixed over transparent epoxy wells with internal cavities to simulate a pulpal chamber. This chamber was filled with an enzymatic reagent to simulate pulpal fluid. The bleaching gels were applied on enamel surface and the image of the pulpal fluid was captured by a video camera to monitor the time of peroxide penetration in each specimen. ANOVA analysis showed that concentration and type of activation of bleaching gel significantly influenced the diffusion time of HP (P < 0.05). 35% HP showed the lowest diffusion times compared to the groups with 20% HP gel. The light activation of HP decreased significantly the diffusion time compared to chemical activation. The highest diffusion time was obtained with 20% HP chemically activated. The diffusion time of HP was dependent on activation and concentration of HP. The higher concentration of HP diffused through dental tissues more quickly.

Temperature variation caused by high-intensity LED curing lights in bovine dentin.

This study sought to evaluate the temperature variations in bovine dentin when cured with high-intensity LED appliances and quartz-tungsten-halogen (QTH) appliances. Forty-five slices of bovine dentin (0.7 mm thick) were divided into three groups. Temperature variations were measured during polymerization of the adhesive (10 seconds), during polymerization of the resin composite (40 seconds), and 24 hours after the resin composite polymerization. The data were submitted to the ANOVA repeated measures test, which showed a statistically significant difference in the interaction factor (p = 0.0001). Tukey's test (p = 5%) revealed that the SmartLite PS LED appliance caused a significantly higher temperature increase than the other appliances following polymerization of the adhesive, that both LED appliances produced significantly greater temperature increases than the QTH curing light during polymerization of the resin composite, and that the SmartLite PS produced the greatest temperature increase after 24 hours.

Polymerization efficiency of high-intensity LEDs with different exposure times.

This study compared two high-intensity light-emitting diode (LED) appliances to a quartz-halogen-tungsten (QTH) appliance and measured their ability to polymerize resin composite efficiently. Eighty-four test specimens (2 mm x 5 mm) were made of resin composite and exposed to one of the two LED appliances for 10, 20, or 40 seconds; the QTH appliance was used as a control group for 40 seconds. It was concluded that using the high-intensity LEDs for 20 seconds produced microhardness similar to that produced by using the QTH appliance for 40 seconds, but the high intensity LEDs did not improve depth of cure.

Avaliação do desgaste superficial do esmalte escovado com dentifrícios e submetido à ação de agentes branqueadores / Evaluation of the superficial enamel wear brushed with dentifricies and submitted to bleaching agents

O objetivo deste trabalho foi o de avaliar quantitativamente a ocorrência de alterações superficiais do esmalte quando submetifo ao branqueamento dental noturno por dez dias com peróxido de carbamida 10 por cento e escovação com três diferentes dentifrícios. Foram empregadas as coroas de trinta incisivos bovinos que foram divididas em três grupos, A - escovado com Sorriso Branqueador, B - Sorriso e C - Close up com micropartículas, cada um contendo dez dentes. Cada grupo teve as coroas dentais seccionadas longitudinalmente em duas metades e incluídas em resina acrílica, com a face vestibular voltada externamente, de modo a ficarem dispostos lado a lado, possibilitando a subdivisão de cada grupo em dois sub-grupos, sendo que A1, B1 e C1 receberam o tratamento branqueador (aplicação do agente branqueador por 12 horas e três escovações diárias com os respectivos dentifrícios) e A2, B2 e C2 somente as escovações. Entre as escovações, os grupos foram imersos em saliva artificial a 37 ñ 1°C. As superfícies de esmalte foram medidas em máquina de ensaio de medição tridimensional antes e depois de realizado o branqueamento e/ou escovações. Na condição com clareador, a análise estatística (teste Kruskal-Wallis, e teste de Dunn, a=5 por cento, kw=6,073; gl=2; p=0,048), indicou que o grupo A difere estatisticamente do grupo B enquanto o grupo C não difere dos demais. Este estudo in vitro, sugere que dentifrícios mais abrasivos podem induzir a uma perda superficial maior do esmalte quando este está sendo submetido ao tratamento branqueador