Effect of rotational forces on the durability of dental materials: implications in biology and anthropology

Both natural and synthetic prosthetic teeth undergo mechanical degradation, impacting their durability. Experimental studies typically simulate dental contacts using simple configurations involving normal and lateral forces. While often necessary due to the constraints of apparatus set-ups and mathematical models, these assumptions oversimplify the complex conditions during mastication and ignore poorly understood but potentially important rotational forces, which occur when teeth are compressed into the alveolar bone. We investigate the influence of rotational forces on contact damage/wear in synthetic dental materials using advanced equipment with decoupled biaxial actuators. Cyclic contact loads combining compression (50 N) and rotation (30°) are applied to zirconia (Z), composite (CP), feldspathic (F) and lithium silicate based (ZLS) glass-ceramics. After 105 cycles, Z exhibits the greatest wear resistance (wear volume 4.16 × 10-4 mm3), followed by F (5.83 × 10-3 mm3), CP (9.17 × 10-3 mm3) and ZLS (1.64 × 10-2 mm3), with p-values 0.004 (Z-F), 0.631 (F-CP), 0.012 (F-ZLS) and 0.009 (CP-ZLS). Abrasion is the primary wear mode, with specific mechanisms such as plastic deformation and microfracture varying with material microstructure. Contact mechanics analysis indicates that rotational forces induce lower wear than non-rotational sliding. Potential implications in dentistry, biology and anthropology are discussed, including the design of culturally and behaviourally informed dental prosthetics.