PURPOSE: To compare the wear of an enhanced resin-modified glass-ionomer (RMGI) restorative material (ACTIVA BioACTIVE Restorative) to a resin composite (Filtek Supreme Ultra), RMGI (Fuji II LC), and glass-ionomer (GI) (Fuji IX) material.METHODS: Specimens of each material (n = 8) were prepared in a silicone mold. All specimens other than the GI material were light polymerized for 40 seconds. After 24-hour storage (H2O, 37 degrees C), the specimens were loaded into the modified Alabama wear testing device. Freshly extracted cusps of human premolars were prepared as antagonists. Specimens were loaded with 20N for 100,000 cycles at 1 Hz. A 33% glycerin lubricant was cycled throughout testing. Specimens and enamel antagonists were scanned before and after wear testing with a non-contact optical profilometer and volumetric wear was measured with superimposition software. Representative specimens were examined with scanning electron microscopy. Data were analyzed with a 1-way ANOVA and Tukey post-hoc analysis (alpha = 0.05).RESULTS: Significant differences were found between materials. Materials ranked in order of increasing wear: Filtek Supreme Ultra and ACTIVA BioACTIVE Restorative < Fuji II LC < Fuji IX. Micrographs revealed that Filtek Supreme Ultra and ACTIVA BioACTIVE Restorative underwent abrasive wear whereas Fuji II LC and Fuji IX underwent fatigue wear.