Methods: Six experimental RBCs modified from a commercial RBC were tested where disc-shaped specimens (13.0 ± 0.1 mm diameter and 2.0 ± 0.1 mm height) of each RBC were irradiated at 540 ± 14 mW/cm2. Short-term three-body wear simulation was carried out in the Oregon Health Science University (OHSU) four chamber oral wear simulator for 50,000 cycles and long-term was performed up to 300,000 cycles. The wear facets were analysed using a non-contact optical profilometer. One-way analysis of variance (ANOVA) were made at P=0.05, guided as necessary by Tukeys correction in multiple partial analyses of the mean total volumetric wear and mean maximum wear depth.
Results: The filler was dominant over the resin in terms of mechanical properties namely short- and long-term wear behaviour. Increasing the filler fraction (71.4 to 76vol%) and mean filler diameter (1.5 to 2.5 mm) significantly decreased (P<0.001) the long-term wear behaviour but increasing the filler density resulted in a significant increased (P<0.001) the long-term wear behaviour.
Conclusions: For each RBC monomeric resin and filler (type, density and diameter) combination employed, a finite filler volume fraction exists. Operating at the finite filler volume fraction increases the difficulty in improving the mechanical properties of the RBCs tailored from a commercial product although the filler was dominant over the resin in terms of wear performance.