The clinical wear of three posterior composites

The wear of three posterior composites and two amalgams was assessed clinically and measured on replica models. For the composite restorations abrasion was measured as the depth of enamel exposed at the cavity margin. Attrition was measured for all materials as the depth of surface wear determined by laser interfereometry. For the posterior composites the mean abrasion was: Clearfil 79.2 microns, Occlusin 175.9 microns and P-30 96.1 microns. The corresponding values for attrition were: 153.4 microns, 205.9 microns and 255.5 microns, respectively. The attrition of the two amalgams was: New True Dentalloy 120.8 microns, Solila Nova 115.3 microns. Therefore, attrition was greater than abrasion and the attrition of the three composites was greater than that of the two amalgams. Abrasion was affected by local factors, including the marginal contour of the restoration, whereas attrition was largely a function of the properties of the material itself. These findings indicate that composites should not be considered as a direct alternative to amalgam, especially in patients with high occlusal stress.