Dental bleaching agents with calcium and their effects on enamel microhardness and morphology

Aim: To evaluate enamel microhardness and morphology after bleaching with hydrogen peroxide containing calcium in different concentrations. Methods: One hundred specimens of human teeth were ground and polished and had the initial microhardness evaluated. The specimens were randomly assigned into five groups (n=20): Group 1 - Control group (no treatment); Group 2 - Home Peroxide 6% (without calcium); Group 3 - Home Peroxide 7.5% (without calcium); Group 4 - White Class 6% (with calcium); Group 5 - White Class 7.5% (with calcium). For each group, the bleaching was performed according to the manufacturer's specifications. The specimens were bleached once a day for 5 days and subjected to pH cycling. Microhardness and scanning electron microscopy (SEM) analysis were performed before and after bleaching. Results: The results showed that groups submitted to bleaching treatment presented hardness loss compared to the control group. The group of 7.5% hydrogen peroxide with calcium showed a lower percentage of hardness loss in relation to other groups. Conclusion: Calcium in association with a higher hydrogen peroxide concentration may decrease microhardness changes on enamel.

Avaliação da microdureza em resinas compostas fotopolimerizadas com sistemas de luz halógena e diodo emissor de luz / Evaluation of microhardness on polymerization's photo of resin composites by helogen light and light emitting diode

O objetivo deste estudo foi o de avaliar a microdureza de duas resinas compostas, uma compactável (Tetric Ceram) e outra do tipo flow (Tetric Flow), utilizando-se duas fontes de luz, uma halógena e outra à base de diodo emissor de luz (LED). Foram confeccionados quarenta corpos de prova, utilizando-se uma matriz de teflon, e divididos em quatro grupos: Grupo I - Tetric Ceram Halógena; Grupo II - Tetric Ceram LED; Grupo III - Tetric Flow Halógena e Grupo IV - Tetric Flow LED. Após o lixamento e polimento dos corpos de prova, foi realizada a análise da microdureza (Vickers) nas regiões de topo e de base em cada amostra. A análise de variância (ANOVA) e o teste de Tukey foram aplicados ao nível de significância de 5%. Os resultados mostraram que a fonte de luz halógena foi estatisticamente mais efetiva (p=0,05) que o LED na microdureza superficial; quando comparados os tipos de resina compostas, a Tetric Ceram apresentou valores de microdureza estatisticamente maiores (p,<,05) que a Tetric Flow, e as regiões de topo apresentaram microdureza maior (p<0,05) em relação às regiões de base, independente da fonte de luz e do material resinoso utilizado. Os resultados sugerem que a fonte de luz halógena é mais efetiva que o LED.

The light curing of resin composite by halogen light is frequent in dental. Therefore the emitting diodes (LEDs), have been suggested in opposite to halogen light, which can present more advantages. The aim of this study was to evaluate the microhardness of the two resin composites, a condensable resin (Tetric Ceram) and other flow resin (Tetric Flow), using two light curing units, a halogen light (Ultarlux EL) and a LED (Ultraled XP). Forty specimens (5x5x6mm) were obtained using a matrix of teflon and dividing in four groups: Group I - Halogen Tetric Ceram; Group II - LED Tetric Ceram; Group III - Halogen Tetric Flow e Grupo IV - LED Tetric Flow. After the sandpaper and the polish of specimens, the Vickers' microhardness analysis on top and base was measured in all specimens. The values obtained were submitted to a two-way variation of ANOVA analysis and the pared test t (Student's) to level of 5% significance. The results showed that source halogen light was more effective (p?0,05) than LED. When two types of resin composite were compared, the Tetric Ceram presented microhardness values higher (p?0,05) than Tetric Flow and the top regions obtained microhardness values higher (p?0,05) in relation to base regions independently of light unit used. The results suggest that halogen light curing unit is more effective than LED.