The frictional coefficients and associated wear resistance of novel low-shrink resin-based composites

Objectives. Frictional forces play a major rote in the oral wear process of dental resin-based composites (RBCs) and it would be of interest to consider how the energy from friction is dissipated at the material surface. Consequently, the micromechanical wear properties of conventional methacrylate compared with novel oxirane RBCs were assessed. Method. The frictional coefficient (p), volume loss and Vickers hardness number (VHN) of oxirane (EXL596 and H1) and methacrylate RBCs (Z100 and Fittek(TM) Z250) were evaluated. Archard's wear equation was implemented to obtain the wear coefficient (K) and expressed as a 'fraction of friction' (K/mu) to indicate the dissipation of frictional energy that resulted in wear. Scanning electron microscopy (SEM) was used to qualitatively asses the wear facets of each RBC following 50000-cycles. Results. The mean frictional coefficients observed between the oxirane and methacrylate RBCs were not significantly different (P> 0.05). However, the volume toss of EXL596 and H1 (5.9 +/- 0.4 and 4.7 +/- 0.3 X 10(-2) mm(3)) was significantly increased compared with Z100 and Filtek(TM) Z250 (1.7+/-0.2 and 2.3+/-0.3 X 10(-2) mm(3)). The VHN of EXL596 and H1 was either significantly greater (P = 0.021) or similar (P=0.089) to Filtek(TM) Z250, respectively. An increase in K/mu was reported for EXL596 and H1 (34.7+/-4.1 and 22.8+/-2.4x10(-4)) compared with Z100 and Filtek(TM) Z250 (8.50 +/- 0.7 x 10(-4) and 8.62+/-1.0x10(-4)) (P