The relationship between physical parameters and wear of dental composites

Materials and methodsA wear method was developed that mainly simulates attrition wear using a commercially available chewing simulator (Willytec, Germany). In this test, a standardized stylus made of pressable ceramic (Empress) hits flat specimens 120,000 times with a 5 kg weight, a descent speed of 60 mm/s and a lateral movement of 0.7 mm with a speed of 40 mm/s under constant exchange of water at different temperatures (325 × 5 °C/55 °C). The volume loss was measured on plaster replicas with the Laserscan 3D (Willytec) and the Match 3D software. Twenty-four experimental and commercial composites (n = 8) were tested with a volumetric wear range of between 5.5 and 147 × 10−2 mm3. On standardized specimens made of the same composites, the Vickers hardness (H), elastic modulus (E) and fracture toughness (K1c) were measured. The mean particle size (d  ) and volume content (vfvf) of the inorganic filler were evaluated. Furthermore, a differentiation was made between the main filler with the largest mean size (d1, vf,1vf,1) and the total filler content (vf,totvf,tot).ResultsThe best linear regression curve fit with an adjusted R2 of 0.908 was found forwear index=d10.6K1cvf,1vf,tot(E/H).ConclusionsThe good mathematical fit of the formula may be an indication that the wear method is based on physical properties and that it provides a highly reproducible standard.