This study investigates the wear resistance of four different types of occlusal splint materials based on two-body wear simulations under wet and dry conditions. Twenty specimens of each splint material (Dentalon Plus, Orthoplast, Biocryl C, and Eclipse), each with a diameter of 16 mm and a thickness of 3 mm, were tested, half under wet and half under dry conditions. Each wear test was performed using a device called chewing simulator CS-4 (n = 10; test load: 50 N; number of cycles: 10 000, 20 000, and 30 000; continuous rinsing with 30 degrees C water for wet conditions); the antagonists were simulated using steel balls. Wear was determined using a 3D laser scanner and a surface analysis program. To detect significant statistical differences, wear data after 10 000; 20 000; and 30 000 cycles were compared using the KruskalWallis test and the MannWhitney U-test. The level of significance was set at 5%. Significant differences were found between the groups of different materials tested under wet conditions (P < 0.05), whereas no differences between them were found under dry conditions (P > 0.05). No significant difference was found between the wet and dry conditions for all materials and cycles (P > 0.05). For groups of different materials tested under wet conditions, the degree of volume loss generated in the Chewing Simulator CS-4 was found to differ significantly for different numbers of cycles. The presence of water had no effect on the volume loss in the different material groups that were tested.