Objective of the study: to measure the in vitro wear of two bioactive smart composite restorative materials and one glass ionomer cement. Materials and methods: The smart composites Activa (Pulpdent) and Cention N (Ivoclar Vivadent) and the glass ionomer cement Fuji IX (GC) were applied into aluminum sample holders, pressed against a glass plate and stored in water for 3 weeks after curing. The samples were subjected to 400,000 load cycles of 49 N in the CS-4 chewing simulator (Mechatronik) against steatite antagonists and subjected to 4,440 thermocycles from 5 °C to 55 °C. Samples were evaluated with replicas after 5,000, 10,000, 20,000, 40,000, 60,000, 80,000, 100,000, 120,000, 160,000, 200,000, 240,000, 280,000, 320,000, 360,000 and 400,000 cycles with a laser scanner (LAS-20, Mechatronik) and the Geomagic software (wear volume). The data was analyzed with ANOVA and Tukey test. Selected wear facets were analyzed with a scanning electron microscope (SEM). Results: The increase in wear was almost linear and after 60,000 cycles significantly different depending on the material (Activa Cention N Fuji IX). After 400,000 load cycles the following wear was measured: Activa 1.571 mm3, Cention N 2.455 mm3 and Fuji IX 5.622 mm3. The wear of the antagonist was slight and in the reverse order (p 0.001): Fuji IX 0.021 mm3, Activa 0.091 mm3 and Cention N 0.126 mm3. SEM analysis showed pores in the powder-liquid systems. The composite and their antagonists had scratched surfaces, something that was not seen on the glass ionomer cement. Discussion: The bioactive composites that were tested had wear values comparable to the modern hybrid composites determined by the authors with the identical test method. The lesser wear of Activa in comparison to Cention N can be explained by the fact that the latter material is designed as a powder-liquid system with manual mixing. Conclusion: Based on their wear behavior the tested bioactive smart composites are suitable for posterior fillings (as an amalgam replacement) while the great wear to the glass ionomer cement confirms this indication (non load-bearing class I and II fillings). University of Florida, College of Dentistry, Department for Restorative Dental Sciences, 1395 Center Drive, Gainesville FL 32608 USA: Prof. Dr. Jean-François Roulet, Dr. Hind Hussein BDS, Dr. Nader F. Abdulhameed BDS. MS. PhD Cand., Chiayi Shen Ph.D. Keywords: alcasites, glass ionomer cement, in-vitro-wear, smart composites