RESUMO
OBJECTIVES: The aim of this study was to evaluate the effects of different light sources and curing time on the degree of conversion and microhardness of two surfaces within a nanofilled composite resin. METHODS: Four experimental groups (n=10) were formed in accordance with the light source (quartz-tungsten halogen (QTH - 600mW/cm(2)), or light-emitting-diode (LED - 800mW/cm(2))) and the time of curing (20 s or 40 s). The specimens were prepared with a circular mould (5 mm ∅ and 2 mm thick), according to the respective protocol, and the Knoop microhardness and degree of conversion was measured at the top and the base of the specimens. The degree of conversion was evaluated by the Fourier transform infrared spectrometer (FTIR). The results were analyzed by ANOVA two-way repeated measures and Tukey's test (α=,05). RESULTS: Both the degree of conversion and microhardness were higher at the top than at the bottom of the specimens. The QTH light source presented better values on the degree of conversion evaluation, but this result was not observed in the microhardness evaluation. Although forty seconds of curing promotes an increased level of microhardness, it did not influence the degree of conversion. CONCLUSION: It could be concluded that increasing the time of curing to 40 s promotes an increase in microhardness, but it does not influence the degree of conversion of a nanofilled composite resin. QTH promote better monomeric conversion; however, the microhardness values are similar to LED curing. For all situations tested, the bottom of the specimens presented lower results than the top.
RESUMO
O objetivo desta pesquisa "in vivo", foi estudar as possíveis alterações histopatológicas causadas, pela luz emitida por um aparelho fotopolimerizador, que apresenta um comprimento de onda oscilando entre 400 nm a 520 nm e uma intensidade de luz de 420 mW/cm2 a 600 mW/cm2. Foram utilizados 21 coelhos da raça Nova Zelândia, adultos que recebiam a exposição da luz azul encostado a pele do lábio ou a uma distância de 10 cm do olho. Os tempos de exposição variaram de doses unitária de 10 segundos até 30 minutos intercalados por dia durante 6 meses. Após os tempos estabelecidos para cada grupo, os animais eram anestesiados e sacrificados e tinham os segmentos da pele expostos e seus olhos submetidos à tramitação laboratorial de rotina para análise histológica. Os resultados obtidos através de comparações com os que não foram expostos à luz, mostraram que as estruturas analisadas, não sofreram alterações histológicas nestes períodos de exposição à luz
The aim of this "in vivo" research, was to study the possible histopathological changes caused by a light resin-curing with 420 to 600 mw/cm2 and 400 nm to 520 nm wave length. There were used 21 adult New Zealand rabbits, which were exposed to a blue light, either touching the lip skin or 10 cm far away from their eyes. The expouse time ranged from 10 sec. unitary dose till 30 minutes a day during 6 months. Once complete the exposition periods, the animals were anesthethyzed and sacrified, and had their exposed skin areas and eyes, submitted to histopathological routine analysis. The control group were not exposed to light. Based in our results, it was concluded that the analysed structures did not show any histopathological changes after the light exposure periods