Methods: Four experimental RBCs derived from a control commercial formulation (Grandioso, Voco; Resin: BisGMA:TEGDMA–3:1 ratio; filler: 1.5µm diameter barium–alumina borosilicate particles at 71.4%vol.) varied in the resin composition, average filler size and filler content: G1) BisGMA:TEGDMA–3:1 ratio, 1.5µm diameter filler at 74.5%vol.; G2) UDMA:aliphatic dimethacrylates–1:1 ratio, 1.5µm diameter filler at 74.5%vol.; G3) BisGMA:TEGDMA–3.5:1 ratio, 2.5µm diameter filler at 73%vol.; G4) Ormocer, 2.5µm diameter filler at 73%vol.Ten specimens (13mm length x 10mm width x 2.5mm depth) of each RBC were fabricated on the outer surface of a test wheel. The test wheels were mounted in the ACTA machine against an antagonist steel wheel with a spring force of 15N. A medium containing rice and millet seed shells in aqueous solution was used as a third body. The wear depth on the RBC surface was measured after 200000 contact cycles using a profilometer. Data were submitted to one-way analysis of variance and Tukey’s test (µ=0.05).
Results: Significantly reduced wear depth (p<0.001) was observed for the commercial RBC (Grandioso: 15.8±1.0µm) compared with the experimental RBCs. A non-significant homogeneous grouping of the wear depths was observed for G1 (21.9±2.1µm) and G2 (21.3±2.5µm); however, G3 (26.5±3.1µm) and G4 (37.8±3.2µm) were significantly increased (p<0.001).
Conclusions: Experimental RBCs with smaller filler particles and higher filler volume fraction, in the specified BisGMA:TEGDMA or UDMA:aliphatic dimethacrylates resins, showed reduced wear depth compared with compositions using larger filler particles and lower filler volume fraction. Amongst the compositions using larger filler particles, the experimental RBC containing BisGMA:TEGDMA monomer mixture exhibited significantly lower wear depth than the Ormocer organic matrix.