The purposes of this study were to evaluate the sealing ability of different glass ionomer cements (GICs) used for sandwich restorations and to assess the effect of acid etching of GIC on microleakage at GIC-resin composite interface. Forty cavities were prepared on the proximal surfaces of 20 permanent human premolars (2 cavities per tooth), assigned to 4 groups (n=10) and restored as follows: Group CIE - conventional GIC (CI) was applied onto the axial and cervical cavity walls, allowed setting for 5 min and acid etched (E) along the cavity margins with 35% phosphoric acid for 15 s, washed for 30 s and water was blotted; the adhesive system was applied and light cured for 10 s, completing the restoration with composite resin light cured for 40 s; Group CIN - same as Group CIE, except for acid etching of the CI surface; Group RME - same as CIE, but using a resin modified GIC (RMGIC); Group RMN - same as Group RME, except for acid etching of the RMGIC surface. Specimens were soaked in 1% methylene blue dye solution at 24ºC for 24 h, rinsed under running water for 1 h, bisected longitudinally and dye penetration was measured following the ISO/TS 11405-2003 standard. Results were statistically analyzed by Kruskal-Wallis and chi-square tests (a=0.05). Dye penetration scores were as follow: CIE - 2.5; CIN - 2.5; RME - 0.9; and RMN - 0.6. The results suggest that phosphoric acid etching of GIC prior to the placement of composite resin does not improve the sealing ability of sandwich restorations. The RMGIC was more effective in preventing dye penetration at the GIC-resin composite-dentin interfaces than CI.

Esse estudo testou as hipóteses de que: 1. maior tempo de fotopolimerização (TF) produz maior dureza superficial em diferentes profundidades (0 e 3 mm) de resina composta (RC); 2. a cor escura (A3) de RC exige maior TF do que a RC clara (A1) para obter o mesmo grau de D. Foram fabricados 24 corpos-de-prova para cada cor de RC em único incremento de 3 mm (Z100), dividindo-os em 3 grupos (n=8), de acordo com os TF (400 mW/cm²) na superfície superior (S): A1-10 e A3-10: 10 s; A1-20 e A3-20: 20 s; A1-40 e A3-40: 40 s. Os corpos-de-prova foram armazenados sem luz, a 37ºC por 24 h, antes de aferir o grau de dureza nas superfícies S e inferior (I) com um durômetro. Foram realizadas 3 penetrações Vickers em cada superfície (S e I) dos corpos-de-prova (n=24). As diagonais das penetrações foram medidas e os valores de dureza calculados. ANOVA e Tukeyforam usados nas análises estatísticas (a=0,05). Ocorreram diferenças significativas entre S e I para cada combinação de cor-TF (p=0,0001) e entre os TF de mesma combinação cor-superfície (p=0,0001), exceto entre A1S20 e A1S40, confirmando a hipótese 1, mas rejeitando parcialmente a hipótese 2.

This study tested the following hypotheses: 1. increasing light irradiation time (IT) produces greater values of superficial hardness on different depths (0 and 3 mm); and 2. a dark shade composite (A3) needs longer IT than a light shade composite (A1) to produce similar hardness. Disk-shaped specimens (n=24 per shade) were fabricated using a 3-mm-thick increment of composite resin (Z100). Specimens were randomly assigned to 3 groups (n=8) according to the IT (400 mW/cm2) at the upper (U) surface: A1-10 and A3-10: 10 s; A1-20 and A3-20: 20 s; A1-40 and A3-40: 40 s. Specimens were stored in black lightproof containers at 37ºC for 24 h before indentation in a hardness tester. Three Vickers indentations were performed on the U and lower (L) surfaces of each specimen. The indent diagonals were measured and the hardness value calculated. The results were analyzed statistically by ANOVA and Tukey's test (alpha=0.05). Statistically significant differences were found between U and L surfaces of each composite shade-IT combination (p=0.0001) and among the ITs of same shade-surface combination (p=0.0001), except between groups A1-20U and A1-40U, confirming the study hypothesis 1 and partially rejecting the hypothesis 2.