The friction and wear behavior of dental ceramics (Vita VMK95) against uniform Si3N4 balls has been investigated using a small amplitude reciprocating apparatus under simulated oral conditions. The variables of ball radii (2mm, 6 mm, 13mm, and 21mm), load (10N, 20N, 30N, and 40N), reciprocating amplitude (200(m), frequency (2Hz) and use of artificial saliva lubrication or no lubrication were selected. Tests lasting up to 10,000 cycles were conducted. The wear scars of the samples were characterized with 3-D con focused laser-scanning microscope. The wear depths were analyzed statistically. The correlations between the wear behaviors and antagonist radii were also compared. The results show the friction coefficient of dental porcelain goes up with the decreasing of antagonist radii, and the wear depth decreases with the antagonist diameters. Load and lubrication effect is significant for friction coefficient and wear depth. The friction and wear mechanism of dental ceramics was characterized by abrasive wear and delaminating.