Method: The Pin-on-Disc (PoD) method was used to measure the frictional sliding wear between GIC discs and a ceramic antagonist pin (3mm diameter). Two commercial GICs were used according to the manufacturers’ recommendations: Equia (GC Europe, Leuven, B) and Chemfil Rock (Dentsply, Konstanz, G). The wear tests (n=10) were performed in balanced electrolyte solution at 23°C at a constant sliding speed of 45 rpm. The static normal force on the pin was set to 14.1 N (2MPa) perpendicular to the wear surface. The resulting sliding force was continuously recorded using a 50N load cell. After 40.000 wear cycles, the mean wear depths were measured using an optical profilometer (CT100 Cybertechnologies, Ingolstadt, G) with a scan head of ± 0.2µm z-resolution. The COFs were calculated as the ratio between friction force and the applied normal force. The wear depth and sliding force data were analysed using ANOVA (α=0.05).
Result: The wear depth for Equia was significantly reduced (38.97 ± 12.8 µm) compared to Chemfil Rock (48.52 ± 8.3 µm) as well as the sliding force after 40.000 wear cycles (5.24 ± 0.1 N (Equia) versus 7.82 ± 0.2 N (Chemfil Rock)). COFs were 0.37 and 0.55, respectively.
Conclusion: The superior results for Equia are most probably due to the resin coating layer. The finer cement microstructure might have further contributed to the reduced COF for Equia. The coating layer thickness was measured 30-50 µm, thus accounting for a complete removal during the test runs. COFs were measured for a specific material pairing (cement-alumina) and highly influenced by process variables and lubricant solution.