The influence of antagonist standardization on wear

For differences among materials to be easily detected, low variation in in vitro wear tests is desirable. The working hypothesis of this paper was tha t antagonists standardized for shape and size and according to materials wo uld show mean values similar to those found in natural, non-standardized cu sps, and that standardization would lead to a reduction in mean variation. First, the shapes and sizes of palatal cusps of non-erupted human upper thi rd molars were measured. The cusp cupola was best described by the formula y = 0.001 x(2) and was symmetrical around the axis of rotation. Up to 200 m u m of the y-axis, this parabola corresponded best to a ball radius of 0.6 mm. Based on this information, standardized antagonists were fabricated fro m both human enamel and steatite. Wear in the occlusal contact area and the wear of opposing conventional ceramic and fine hybrid composite, respectiv ely, were quantified in a computerized chewing simulator. As a control, nat ural human enamel cusps were used. Standardization of enamel cusps did not reduce the variation of the resulting wear compared with that of non-standa rdized enamel antagonists. Furthermore, standardization led to significantl y different results both in the antagonists and in the opposing restorative materials. Thus, natural enamel antagonists are preferable for the simulat ion of wear in the occlusal contact area.