Effect of Tooth Brushing on the Surface of Bulk-Fill Composites

Objectives: This study evaluated the effect of the light-activation with two curing units on the surface roughness (SR), microhardness (SM) and volume loss (VL) of three bulk-fill composites after tooth brushing.
Methods: Valo (Ultradent) and Demi Ultra (Kerr) curing units were used for 10 seconds to polymerize three bulk-fill composites: Surefil SDR Flow (SDR - DENTSPLY), Tetric N-Ceram Bulk Fill (TET - Ivoclar Vivadent) and Filtek Bulk Fill Posterior (FBF - 3M ESPE). Composite resin disks that were 2 mm thick and 1 cm diameter were prepared and the cured surface was lightly polished with aluminum oxide paper (600-grit). Adhesive tape was placed over half the composite disks (control area) and other half was submitted to brushing (30,000 cycles), using soft toothbrush and toothpaste (Oral-B Pro-Health). The SM was determined in control and brushed areas. Composite disks were also analyzed regarding SR and VL using confocal microscope (LXTOLS 4000, Olympus). SR data was analyzed by Paired-T test and VL and SM were analyzed by two and three-way ANOVA and post-hoc Tukey test (α=0.05).
Results: The SR of FBF light activated with Demi Ultra was not affected by brushing. TET showed higher VL when polymerized with Valo, while for Demi Ultra higher VL was observed with SDR. Higher SM was always found with FBF, followed by TET and SDR. Light activation of TET with Valo resulted in higher SM than when cured with the Demi Ultra, while no difference was noted for SDR and FBF.
Conclusions: Brushing can alter the SR of bulk-fill composites. All composites presented VL of their surface mass after brushing, but the amount of VL of SDR depended on the type of curing unit used. The choice of light curing unit affects the SM of some composites.