Effect of delayed start of light-curing on microtensile bond strengths of two adhesives bonded to dentin

Abstract

The aim of the present study was to evaluate the microtensile bond strength to dentin (µTBS) of two total-etching adhesives applied with delays of 1–30s for curing. Fifty extracted molar teeth were used. Occlusal enamel was sectioned to expose flat dentin surface, which was further polished with 600-grit paper for smear layer standardization. The specimens were divided into two groups, G1: Single Bond total-etching adhesive (SB), and G2: Prime & Bond NT total-etching adhesive (PB). Each group was further divided into 5 subgroups according to the delayed light-cure initiation after the adhesive systems application (n=5): Subgroup 1s – 1s; Subgroup 5s – 5s; Subgroup 10s – 10s; Subgroup 20s – 20s; Subgroup 30s – 30s. Composite resin cones 5mm height and 10mm in diameter were fabricated. Specimens were stored in distilled water at 37°C for 24h and sectioned to obtain 1×1mm2 transversal specimens. Specimens were thermocycled and µTBS was measured. Data were submitted to two-way ANOVA (AdhesiveXDelay time) and Tukey׳s test. The level of significance was set at 5%. The results in mean MPa(±SD) for interaction between adhesive and delay time were: PB/1s – 23.82± 2.54a; SB/5s – 19.52± 2.67b; PB/5s – 18.56± 3.06bc; SB/1s – 15.49± 2.69cd; SB/20s – 16.33± 2.55d; SB/10s – 13.88 ±1.67d; PB/10s – 11.04 ±1.28e; PB/30s – 10.89± 1.31e; PB/20s – 10.24± 2.33e; SB/30s – 9.19±1.91e. It was concluded that light-cure initiation timing of total-etching adhesives interferes negatively with µTBS to dentin.