Several mechanical properties of experimental composites and an unfilled resin were studied. The dynamic Young's modulus was measured with a non-destructive dynamic method. The Young's modulus and also the transverse strength were determined statically by means of three-point bending. The hardness was studied by means of Wallace indentation depth measurements, and in vitro wear resistance was assessed under stress-bearing conditions. An exponential regression of the results measured for each property as a function of the volumetric filler fraction was appraised. An excellent correlation was found with each property. This exponential mixture rule is proposed for the study of the mechanical properties of isotropic dental composites.