Interaction between staining and degradation of a composite resin in contact with colored foods

Composite resins might be susceptible to degradation and staining when in contact with some foods and drinks. This study evaluated color alteration and changes in microhardness of a microhybrid composite after immersion in different colored foods and determined whether there was a correlation between these two variables. Eighty composite disks were randomly divided into 8 experimental groups (n = 10): kept dry; deionized water; orange juice; passion fruit juice; grape juice; ketchup; mustard and soy sauce. The disks were individually immersed in their respective test substance at 37 ºC, for a period of 28 days. Superficial analysis of the disk specimens was performed by taking microhardness measurements (Vickers, 50 g load for 45 seconds) and color alterations were determined with a spectrophotometer (CINTRA 10- using a CIEL*a*b* system, 400-700 nm wavelength, illuminant d65 and standard observer of 2º) at the following times: baseline (before immersion), 1, 7, 14, 21 and 28 days. Results were analyzed by ANOVA and Tukey's test (p < 0.05). Both variables were also submitted to Pearson's correlation test (p < 0.05). The passion fruit group underwent the greatest microhardness change, while the mustard group suffered the greatest color alteration. Significant positive correlation was found between the two variables for the groups deionized water, grape juice, soy sauce and ketchup. Not all color alteration could be associated with surface degradation.

Intrapupal temperature variation during Er,Cr: YSGG enamel irradiation on carries prevention

Studies have shown the cariostatic effect of Er,Cr:YSGG (2.78 mm) laser irradiation on human enamel and have suggested its use on caries prevention. However there are still no reports on the intrapulpal temperature increase during enamel irradiation using parameters for caries prevention. The aim of this in vitro study was to evaluate the temperature variation in the pulp chamber during human enamel irradiation with Er,Cr:YSGG laser at different energy densities. Fifteen enamel blocks obtained from third molars (3 x 3 x 3 mm) were randomly assigned to 3 groups (n=5): G1 - Er,Cr:YSGG laser 0.25 W, 20 Hz, 2.84 J/cm², G2 - Er,Cr:YSGG laser 0.50 W, 20 Hz, 5.68 J/cm², G3 - Er,Cr:YSGG laser 0.75 W, 20 Hz, 8.52 J/cm². During enamel irradiation, two thermocouples were fixed in the inner surface of the specimens and a thermal conducting paste was used. One-way ANOVA did not show statistically significant difference among the experimental groups (a=0.05). There was intrapulpal temperature variation <0.1ºC for all irradiation parameters. In conclusion, under the tested conditions, the use of Er,Cr:YSGG laser with parameters set for caries prevention lead to an acceptable temperature increase in the pulp chamber.

Tratamento marginal de restaurações cerâmicas com laser de Nd: YAG - avaliação da microinfiltração / Marginal treatment of ceramic restorations using Nd: YAG laser - microleakage evaluation

Introdução - O objetivo deste estudo in vitro foi avaliar a microinfiltração em restaurações de porcelana com tratamento das margens com laser de Nd:YAG (1064 nm). Material e Métodos - Cavidades Classe V para restaurações indiretas, com término em esmalte e cemento/dentina, foram preparadas na face vestibular de 20 dentes bovinos. Após condicionamento ácido e aplicação do sistema adesivo nos preparos cavitários, e tratamento da superfície interna da porcelana com ácido fluorídrico e silano, as restaurações foram cimentadas com cimento resinoso de dupla ativação RelyX ARC (3M ESPE). As amostras foram distribuídas aleatoriamente em 4 grupos (n = 5): G1: controle - sem irradiação; G2, G3 e G4 foram irradiados com laser de Nd:YAG com diferentes parâmetros. Todas as amostras foram imersas em água destilada (37°C, 7 dias) submetidas à ciclagem térmica, impermeabilizadas e imersas em solução de nitrato de prata a 50% (8h). Posteriormente as restauraçõrs foram seccionadas longitudinalmente e imersas em solução fotoreveladora sob luz fluorescente por 16h. O grau de microinfiltração foi avaliado por três examinadores previamente calibrados, através da análise de fotografias, e os valores foram submetidos à análise estatística de Kruskal-Wallis e Mann-Whitney (p < 0,05). Resultados - Os resultados mostraram que em esmalte houve diferença significante entre o grupo controle e os tratados com laser, sem diferença entre os grupos irradiados; em dentina não houve diferença significante entre os grupos. Conclusão - A irradiação com laser de Nd:YAG influenciou negativamente na microinfiltração marginal das restaurações indiretas de cerâmica cimentadas com cimento resinoso