In vitro Wear of Three Bulk Fill Composites

Objectives: The aim of this study was to test the hypothesis that there is no difference in wear in vitro among the composites investigated and their respective antagonists.
Methods: Tetric-N-Ceram Bulkfil (Ivoclar Vivadent; [T]), and X-tra Fil (Voco; [X]), both composites were with multimodal filler, and QuiX (Dentsply; [Q]) were subjected to wear in a chewing simulator (CS 4.8, SD Mechatronik) with steatite balls (Ø 6mm) as antagonists. Eight specimens of each composite (n=8) were made by bulk-packing into a cylindrical cavity (Ø 8mm, depth 1.5mm), light cured (Bluephase G2 1450 mW/cm²) for 10s, polished with Soflex discs (3M ESPE) and stored in distilled water for 3 weeks. They were subjected to 1.2x10⁵ cycles between 0 and 49N with 0.7mm lateral movement at 1 Hz. The specimens were simultaneously thermocycled (5/55°C) every 90s. The wear of the composite and the antagonist in volume was measured with a 3D laser scanner (Laserscanner LAS-20; SD Mechatronik) at prescribed number of cycles.
Results: The total wear of composite in volume was 0.64±0.07 mm³, 0.66±0.08 mm³ and 1.58±0.14 mm³ for [X], [T] and [Q]. The wear of [Q] was significantly greater than [T] and [X] (p<0.0001). The total wear of antagonists in volume was 0.24±0.02 mm³, 0.27±0.02 mm³ and 0.32±0.04 mm³ for [Q], [T] and [X]. The wear of antagonist by [X] is significantly greater than those by [T] and [Q] (p<0.001). The wear between 5,000 and 120,000 wear-cycles was linear and the wear rates were calculated to be 10.46x10³ μm³/cycle, 5.28 x10³ μm³/cycle and 4.41 μm³/cycle for [Q], [T] and [X]. Further analysis shows that there is a negative correlation between the wear of the composite materials and that of the antagonist.
Conclusions: The null hypothesis was rejected.