Wear and Microhardness of Light-cured Composites Versus Pre-cured Composite Blocs

Objectives: The aim of this study was to evaluate the surface microhardness and wear after brushing of different direct light-cured composites versus indirect pre-cured CAD/CAM composite blocs after toothbrushing.
Methods: 160 composite samples were prepared using light-cured (LC) and pre-cured (PC) composites of different manufacturers (n=20): GSO-GrandioSO (LC, Voco), GB-Grandio Blocs (PC, Voco), Z-Z350 XT (LC, 3M/Espe), L-Lava Ultimate (PC, 3M/Espe), K-Kalore (LC, GC), C-Cerasmart (PC, GC), O-Opallis (LC, FGM), B-Brava (PC, FGM). For the PC composite blocs, specimens with 6mm of diameter and 2mm thick were obtained. The LC composites were applied inside a silicone mold with the same dimensions of the PC samples, in a single increment and light-cured. The surface was polished with P1200, P2400 and P4000 SiC sandpaper. The surface microhardness was evaluated using a Knoop microhardness tester. The wear was measured using a contact profilometer comparing the baseline and final profiles. The samples were submitted to 100,000 brushing cycles, using a flat toothbrush under a load of 200g, associated with slurry prepared with a toothpaste (Colgate Total 12, Colgate-Palmolive) and artificial saliva. The data was analyzed using one way ANOVA and Tukey test.
Results: Significant differences were observed for microhardness (p=0.0001) and wear (p=0.0001). The results for microhardness were: K-61.21(±4.02)a, O-65.17(±3.02)ab, B-66.90(±5.08)ab, C-69.28(±5.17)b, Z-83.59(±5.24)c, L-113.74(±8.09)d, GSO-116.09(±8.33)d, GB-130.10(±12.36)e. The results for wear were: GB-6.41(±2.44)a, GSO-8.86(±2.46)ab, L-10.77(±2.65)ab, Z-11.42(±2.72)b, C-17.14(±2.93)c, O-28.94(±8.99)d, K-31.78(±6.38)d, B-47.11(±7.61)e. The groups followed by the same letter do not present significant differences.
Conclusions: For each manufacturer, the pre-cured materials showed higher microhardness than the light-cured ones. Grandio Blocs presented higher microhardness values than all materials tested. The pre-cured materials showed less wear than the light-cured ones, with exception to Brava versus Opallis. Grandio Blocs and Lava ultimate showed less wear than the other pre-cured composites tested. Brava showed more wear the all the other materials tested.