Microhardness of composite resins at different depths varying the post-irradiation time

OBJECTIVE: The purpose of this study was to assess the microhardness of posterior composite resins at different depths varying the post-irradiation time. MATERIALS AND METHODS: For each composite resin [Solitaire 2 (SO) - Heraus Kulzer, P60 (P) - 3M, Prodigy Condesable (PC) - Kerr, Surefil (S) - Dentsply and Alert (A) - Pentron], 6 specimens (3 mm in diameter; 4mm high) were prepared using a black polyurethane cylindrical matrix. The resins were inserted in a bulk increment and light cured for 40 seconds. Microhardness was analyzed at different depths (top, 0.4 mm, 1.0 mm, 2.0mm, 3.0 mm and 4.0 mm) and at two moments (20 minutes and 24 hours after light-curing). Data were analyzed by ANOVA and Tukey's test (p<0.05). RESULTS: Overall, microhardness means decreased significantly with the increase of depth, being lower in the first moment tested. P, S and PC showed the highest microhardness means. CONCLUSION: It may be concluded that the tested composite resins presented a gradual decrease of microhardness as depth increased and this drop was more accentuated for depths beyond 2 mm. For all materials, higher microhardness means were recorded 24 hours after light activation. P60 yielded the best results at the different depths evaluated.

Tensile bond strength of different adhesive systems to enamel and dentin

The aim of this study was to assess the tensile bond strength of four adhesive systems to enamel and dentin: Clearfil Liner Bond 2V - C, Prime&Bond NT/NRC - PB, Single Bond - SB and All Bond 2 -AB. For such purpose, 40 sound human molars were selected. Crowns were bisected in a mesiodistal direction and each half was ground until flat enamel (E) or dentin (D) surfaces were obtained. A total of 80 specimens were randomly assigned to 4 groups (n=20, 10 in enamel and 10 in dentin). After surface treatment, a composite resin (Z250; 3M) cone was prepared using a split Teflon® matrix. Bond strength was tested in an universal testing machine (0.5 mm/min). Bond strength means in MPa were: C - E: 18.66 (±2.67) and D: 21.62 (±5.29); PB - E: 18.13 (±2.96) and D: 3.19 (±1.40); SB - E: 20.06 (±6.11) and D: 16.95 (±2.57); AB - E: 18.20 (±3.94) and D: 15.94 (±4.72). Statistical analysis of data by two-way ANOVA showed that C presented the best results followed by SB. In conclusion, among the tested materials, Clearfil Liner Bond 2V self-etching primer adhesive syetem had the best performance. The substrate type influenced bond strength, being higher to enamel.

Este estudo avaliou a resistência à tração de diferentes sistemas adesivos ao esmalte/dentina: Clearfil Liner Bond 2V - C, Prime&Bond NT/NRC - PB, Single Bond -SB and All Bond 2 -AB. Quarenta molares humanos hígidos tiveram suas coroas seccionadas no sentido mesio-lingual, e posteriormente lixadas até que fossem obtidas superfícies lisas de esmalte (E) ou dentina (D). Oitenta espécimes foi aleatoriamente dividido em 4 grupos (n=20, 10 em esmalte e 10 em dentina). Após o tratamento da superfície de acordo com cada sistema adesivo testado, um cone de resina composta Z250 (3M) foi preparado com uma matriz de Teflon®. O teste de tração foi realizado em uma máquina universal de ensaios (0.5 mm/min). As médias de resistência à tração (em MPa) foram: C - E: 18,66 (±2,67) e D: 21,62 (±5,29); PB - E: 18,13 (±2,96) e D: 3,19 (±1,40); SB - E: 20,06 (±6,11) e D: 16,95 (±2,57); AB - E: 18,20 (±3,94) e D: 15,94 (±4,72). A análise estatística (ANOVA a critérios e teste de Tukey) mostrou que C obteve os melhores resultados, seguido por SB. Concluiu-se que, dentre os materiais testados, o Clearfil Liner Bond 2V teve melhor desempenho, e que o tipo de substrato tratado influenciou na resistência adesiva, sendo esta maior em esmalte.