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

Summary Objectives Frictional forces play a major role 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 ( μ ), volume loss and Vickers hardness number (VHN) of oxirane (EXL596 and H1) and methacrylate RBCs (Z100 and Filtek™ Z250) were evaluated. Archard's wear equation was implemented to obtain the wear coefficient ( K ) and expressed as a ‘fraction of friction’ ( K / μ ) 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 loss of EXL596 and H1 (5.9±0.4 and 4.7±0.3×10 −2  mm 3 ) was significantly increased compared with Z100 and Filtek™ Z250 (1.7±0.2 and 2.3±0.3×10 −2  mm 3 ). The VHN of EXL596 and H1 was either significantly greater ( P =0.021) or similar ( P =0.089) to Filtek™ Z250, respectively. An increase in K / μ was reported for EXL596 and H1 (34.7±4.1 and 22.8±2.4×10 −4 ) compared with Z100 and Filtek™ Z250 (8.50±0.7×10 −4 and 8.62±1.0×10 −4 ) ( P Conclusion The significant decrease in wear resistance of the oxirane compared with methacrylate RBCs was unexpected since frictional coefficients and/or surface hardness were statistically similar. The decreased wear resistance of EXL596 and H1 compared with Z100 and Filtek™ Z250 was further explained by the increase in K / μ from wear theory and the associated increase in surface fatigue identified from SEM. The simplistic testing procedure combined with SEM utilized in the current investigation provided a greater insight into the wear mechanism by considering the effect of frictional energy at the specimen surface which may benefit the development of improved wear resistance for experimental RBC materials.